RE: [Repeater-Builder] Adding capacitors to lower electric bill
The guy did ok on the first part explaining how power factor works but fell down when it comes to the save money part. The utilities do not charge you extra or give you a break if you do or don't have any power factor correction. Unless you are an industrial customer. I have seen demonstrations at shows where the guy trying to sell consumers power factor correction devices had a motor and an ammeter showing current draw. He then switches in a capacitor and shows you how the current drops and shows you how volts times amps reduces the wattage used. Only problem is the electric meter doesn't care what the power factor is! So the utility will bill you the same amount if you use power factor correction or not in your home. The other thing involved if you are going to do power factor correction is that it needs to be done on EACH motor or inductive device. If you just hang a capacitor across the main power line of the proper size when all motors are running it will correct that. But when a motor or other inductive device is shut down and the capacitor is still across the line, now it will have a capacitive load rather than an inductive load. Same problem; capacitive current that is out of phase. You can hook a large AC capacitor across your power line and measure the current thru it. It may look like you are drawing a lot of power thru it but the meter will not see it. Yes it cost the utility more to generate that extra current whether it be capacitive or inductive but you don't pay for it. If the utility was really worried about it they would give incentives for high power factor equipment or they would bill you like they do in industry. We are small potatoes to them. Trying to sell power factor correction to home owners and small business' is a scam. You save nothing on your bill! 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Bon Hal Sent: Saturday, August 21, 2010 2:39 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Adding capacitors to lower electric bill This is a reply to the power issue from a friend of mine: Yes, it's true. Heavy industry uses this technique to reduce their electrical utility costs. Steel production is an example. Some utility companies require that customers with large inductive loads use and pay for capacitor banks to correct the plant's power factor. The issue arises when large inductive loads are connected to the electrical grid. For example, a large horsepower electric motor presents two loads to the grid. One load is the energy consumed or dissipated in work. The other load is inductive. The inductive load stores electrical energy, does not dissipate it, and it is returned to the grid. It can't be helped. It is built into the design of electric motors. This is understandable. We understand that practical electric motor armatures are turned by a strong magnetic field. That magnetic field is produced by large inductors. As an electrical circuit, you can visualize the motor as a resistor in series with an inductor driven by a sine wave 60 Hz alternating voltage source (AC). On the positive half cycle voltage swing (0-180 degrees), electrical energy is dissipated in the load, the resistor. In the resistor the energy is dissipated in heat. In a motor, the energy is dissipated in work done. The inductor stores electrical energy on the positive half cycle then returns the energy to the grid on the negative half cycle (180-360 degrees). The resistor again draws and dissipates energy on the negative half cycle. In the electrical circuit analogy, if the inductor was zero Henrys and the Resistor was non zero Ohms, the Power Factor (PF) is defined as 1.0, or unity. This is a purely dissipative load. If the inductor was non zero Henrys and the Resistor was zero Ohms, the PF is defined as 0.0. This is a purely inductive load. In a practical circuit with some inductance, L, and some resistance, R, PF therefore varies between 0.0 and 1.0. For given values of L and R, PF can be measured or computed. The utility company sells the energy dissipated in a load. If PF = 1.0, the utility company sells all the energy it supplies. As PF decreases due to inductance, the load increasingly stores and returns larger amounts of energy to the utility company. The utility has to generate the additional power needed to charge the connected inductive loads, even if the energy is returned to the grid. The utility needs significantly more capacity and therefore greater investment and operating capital. Worse yet, the increased current flow causes more dissipative energy loss in the line resistance. This inefficiency is a measurable loss of money to the utility. Adding capacitance across and close to the load helps a lot. Briefly and simply, it works like this. The utility initially charges the
RE: [Repeater-Builder] Adding capacitors to lower electric bill
You won't see any difference. The electric meter reads true power not VA. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Friday, August 20, 2010 8:00 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Adding capacitors to lower electric bill A while back, maybe a year or two ago, there was a discussion on here where a list member had success adding a capacitor to his electric service which reduced his bill. It was debated for a while. Anyway, I am wondering if the utility company ever came and replaced the spinning disk meters with electronic versions, and if so, what the outcome was. Could the original poster respond either here or privately? I just today had a similar discussion with another ham who tried essentially the same thing with no success - only his was a commercial model, so it cost him considerably more. Chuck WB2EDV Yahoo! Groups Links
RE: [Repeater-Builder] Polyphaser Question
Here is a little primer on lightning: Having your antenna grounded does not drain off any charge that helps prevent a strike. As a matter of fact grounding the antenna makes it slightly more prone to a strike but not grounding it is much worse as you have no control over what path the energy will take if not grounded. When a storm cloud moves over the area charge builds on objects on the ground. The ground items, towers etc start to emit streamers. When a strike is imminent step leaders come down from the charged cloud and move in approximately 150 foot steps. Changing directions with each step. When a step leader gets close enough to a streamer a connection is made. What follows is a plasma trail which is a very low impedance path that the lightning charge follows. Lightning can be thought of as a current source. In other words if there is a 10 KA strike it is going to develop that much current into whatever it strikes. If for example it hits your tower and the total impedance to ground is quite low then the voltage developed across the tower will be relatively low. But if the ground system is not a good one then the voltage will rise higher. It will still develop the 10 KA current. Bonding all equipment to a common point is one of the first steps to take. Just adding a polyphaser coax protector to the coax line will only equalize the current between center conductor and shield. If power is not protected and everything bonded together the coax protector will do little good. Even without a coax protector, just bonding everything is a great first step. The whole idea is to keep everything at the same voltage level when a strike occurs. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Tony KT9AC Sent: Wednesday, August 18, 2010 9:25 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Polyphaser Question Remember the objective is not to take the brunt of a lightning strike, but to drain off any static that would attract that strike. Lightning is just a spark looking to close the gap, and if your antenna is closer to DC ground, it will find something closer to its potential (i.e. static charged) to hit. Any protection is better than nothing, and don't scrimp on buying the cheapest used protector. Its your equipment your protecting and potentially avoiding liability. I buy new Polyphasers for our site and sleep just fine. On 08/18/2010 08:56 AM, wd8chl wrote: On 8/17/2010 11:55 PM, Ray Brown wrote: What do you do when you want to install a small UHF linking repeater on a 4-story building that has no lightning protection on its' roof? (this is to link an ambulance at a hospital to its' base repeater 40 miles away) From what I've heard, it may not be a good idea to hook it to the HVAC, either. (sigh) Ray, KB0STN No. I would find the nearest copper pipe from either the in-house water system or the sprinkler system, and clamp to that (making sure you don't crimp the pipe!!!) using #6 or maybe #8 wire if it's REALLY close (less then 5') Again, not as good as a dedicated system, but MUCH better then nothing.
RE: [Repeater-Builder] Coax length, etc.
Russ, Of course the Bird 43 does not measure power directly. But it does sample voltage AND current on the line in amounts that are combined to indicate power. It is a directional coupler. The only time you will have a problem with it deviating from its accuracy is when the directivity becomes too low such as when the line impedance is way off from its design 50 ohms. As I said before it will read power accurately even if the transmission line is no a 50 ohm line. The manual even tells you that you can use it to measure line loss with an open at the far end of the line. Please read chapter 2 theory of operation of the Bird manual that you show the reference to. Then read it again! 73 Gary K4FMX Another chance? Which part, erroneous readings, don't directly measure power, or the voltmeter part? Sure, what the heck. ;-) I've had Bird 43's, and calibrated line sections with matched elements for that matter, give erroneous reflected power readings depending upon what was going on with the transmission line. By erroneous, I mean it was usually a reading that was, for example, excessively high versus what we knew was going on, such as a straight piece of rigid line or coax terminated into a known good load. On rare occasion, we found we slipped a bullet or had a bad connector. More often, relocating the instrument somewhere else along the line resolved those bad readings. RF calorimeters can measure power directly. But unless they've one hidden in them somewhere, ThruLine meters can not. Just because the Commission might accept wattmeter readings, or Bird says so, doesn't make it so. As for the voltmeter part, check out page 6 of the Bird 43 manual (page 18 of the PDF), a copy of which you'll recall is here: http://www.repeater-builder.com/bird/pdf/bird-43-wattmeter-2004.pdf I respectfully submit what is shown is a schematic/diagram of a directional coupler attached to a voltmeter as an indicator. An induced RF voltage sample is rectified, filtered and applied through a dropping resistor to a shunt-connected ammeter. By definition, a voltmeter is the shunt-connected ammeter with series resistor part. But don't take my word for it. Take a peek at Chapter 25 in any recent ARRL Handbook (this works for my 2007 copy anyway). Is it less a voltmeter because the induced voltage tracks current on the line? Want to call it an ammeter or current meter then, after all that's what the actual meter movement is? I submit this particular voltmeter happens to be calibrated to read average power at 50 ohms impedance, and it does this quite well within its limitations. I now await your thrashing. Please be gentle. ;-) Like the manual says, the Bird 43 is fast, convenient and accurate. I agree it's fast and convenient. I'll agree it's accurate with the caveats expressed. It beats lugging a slotted line around, and it beats every other meter like it, IMHO, including my old Daiwa dual-metered POS wattmeter. ;-) Oh, BTW, the emperor has no clothes either. :-P 73, Russ WB8ZCC
RE: [Repeater-Builder] Coax length, etc.
nits. It's the next yahoo's turn. ;-) 73, Russ WB8ZCC On 8/15/2010 2:08 PM, Gary Schafer wrote: Russ, Of course the Bird 43 does not measure power directly. But it does sample voltage AND current on the line in amounts that are combined to indicate power. It is a directional coupler. The only time you will have a problem with it deviating from its accuracy is when the directivity becomes too low such as when the line impedance is way off from its design 50 ohms. As I said before it will read power accurately even if the transmission line is no a 50 ohm line. The manual even tells you that you can use it to measure line loss with an open at the far end of the line. Please read chapter 2 theory of operation of the Bird manual that you show the reference to. Then read it again! 73 Gary K4FMX Another chance? Which part, erroneous readings, don't directly measure power, or the voltmeter part? Sure, what the heck. ;-) I've had Bird 43's, and calibrated line sections with matched elements for that matter, give erroneous reflected power readings depending upon what was going on with the transmission line. By erroneous, I mean it was usually a reading that was, for example, excessively high versus what we knew was going on, such as a straight piece of rigid line or coax terminated into a known good load. On rare occasion, we found we slipped a bullet or had a bad connector. More often, relocating the instrument somewhere else along the line resolved those bad readings. RF calorimeters can measure power directly. But unless they've one hidden in them somewhere, ThruLine meters can not. Just because the Commission might accept wattmeter readings, or Bird says so, doesn't make it so. As for the voltmeter part, check out page 6 of the Bird 43 manual (page 18 of the PDF), a copy of which you'll recall is here: http://www.repeater-builder.com/bird/pdf/bird-43-wattmeter-2004.pdf I respectfully submit what is shown is a schematic/diagram of a directional coupler attached to a voltmeter as an indicator. An induced RF voltage sample is rectified, filtered and applied through a dropping resistor to a shunt-connected ammeter. By definition, a voltmeter is the shunt-connected ammeter with series resistor part. But don't take my word for it. Take a peek at Chapter 25 in any recent ARRL Handbook (this works for my 2007 copy anyway). Is it less a voltmeter because the induced voltage tracks current on the line? Want to call it an ammeter or current meter then, after all that's what the actual meter movement is? I submit this particular voltmeter happens to be calibrated to read average power at 50 ohms impedance, and it does this quite well within its limitations. I now await your thrashing. Please be gentle. ;-) Like the manual says, the Bird 43 is fast, convenient and accurate. I agree it's fast and convenient. I'll agree it's accurate with the caveats expressed. It beats lugging a slotted line around, and it beats every other meter like it, IMHO, including my old Daiwa dual-metered POS wattmeter. ;-) Oh, BTW, the emperor has no clothes either. :-P 73, Russ WB8ZCC
RE: [Repeater-Builder] Coax length, etc.
I don't know if you really don't get it or you are just trying to be controversial. I tend to think a little of both. Either way, I give up. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Russ Hines Sent: Sunday, August 15, 2010 7:37 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Coax length, etc. Last round. Hi again, Gary. ;-) On 8/15/2010 7:09 PM, Gary Schafer wrote: Hi again Russ, _ From: mailto:Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Russ Hines Sent: Sunday, August 15, 2010 4:54 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Coax length, etc. I see some folks are heading for the Advil. My apologies. Thanks, Gary, for admitting the 43 doesn't measure power directly. One myth down. Of course, it is a directional coupler, no argument. That makes it a reflectometer, it enables the instrument to isolate forward/reflected samples to some degree of reliability. What's the rest of the circuit? ;-) IMHO, what makes the 43 better than most (if not all) meters of its type, is the directional coupler is a true transmission line coupler, not a ferrite transformer, directly connected capacitor, etc. But it works the same way. Yeah, and? The Bird does it better. As far as rereading the manual, I have been. Bird's explanation requires the reader to suspend a standing wave viewpoint of transmission line theory, and buy into their traveling wave viewpoint. Uh, okay. But that kind of thing sends up red flags for me. I shouldn't have to suspend accepted transmission line theory to understand how their meter works. There are no standing waves that you can measure directly with the Bird meter. In order to truly measure standing waves you need to have a line length greater than a half wave length and measure where the nulls are along the line. Swr is calculated from forward and reflected power at one point on the line with a Bird type of meter. That's correct. As I said, the 43 isn't a slotted line. Regarding VSWR, all in-line meters make an attempt at this, some have fancy cross-needle indicators where VSWR is represented at the intersection of the needles. How else would you do determine VSWR with such a device? That was a rhetorical question. ;-) As it turns out, I don't. When line impedances get away from 50 ohms, accuracy falls and the meter behaves like you'd expect. It tracks whatever current is on the line at that (the meter's) point in the line without regard for impedance. Since it's just not calibrated for whatever that impedance might be, how can it be accurate? The Bird is set up so that the ratio of voltage and current that are detected work out to the power at 50 ohms. When the line is not 50 ohms that voltage/current ratio change that the meter detects. So you can no longer simply look at the scale on the meter and directly read power. For ANY reflected power reading you must subtract the reflected power shown from the forward power shown to find the true power delivered to the load. This holds true no matter what the impedance of the line is. Thanks, Gary, that's right. The meter is calibrated at 50 ohms impedance. When the line impedance isn't 50 ohms, you can't just look at the meter, the meter scale is no longer accurate, is it? Subtracting reflected from forward is a given, and never at issue here. Well, impedance does matter. At the characteristic impedance of the meter, line, load, etc., seems a waste of time to subtract nothing, you'll see right away there's no reflected power. ;-) If the meter did as you suggest, then it would show what the voltage and current are at any point in the line, and therefore be able to tell you what the impedance is at that point, all with some level of accuracy. It simply can't do all that. With the Bird meter you don't care what the impedance is because it measures voltage (by way of capacitive coupling) and current (by way of inductive coupling). Both create voltages that add together in the proper ratio to give the meter reading that represents power level for that combination of voltage and current. Gary, you seem to be contradicting yourself. A paragraph ago you said the ratio of voltage and current work out to the power at 50 ohms. Now we don't care what the impedance is? We either do or don't. As for me, I choose to care 'cuz that's the kind of guy I am. ;-) I understand the coupling, both are present, agreed. But if impedance didn't matter, then the meter would indicate power accurately regardless of line impedance. That's simply not so. The Bird manual even says it's not so. It's limited by its own line section. Yes, Bird describes what happens when using 70 ohm lines with the meter under less-than-perfect conditions. IMHO
RE: [Repeater-Builder] Coax length, etc.
One correction here; the Bird power meter is not just a voltage measuring meter. It does in fact measure voltage and current to calculate power. It will give true power even if used in a non 50 ohm circuit. But you must always subtract reflected power from indicated forward power to find true power delivered to the load. When measuring SWR you must always calculate it (or use the chart) and compare reflected to forward indicated on the meter. It is easy to be fooled as indicated forward power also drops as reflected power drops. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Russ Hines Sent: Saturday, August 14, 2010 4:30 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Coax length, etc.73 Some related comments, if you don't mind. Temperature changes seem to be the biggest detuner of largely mechanical devices like cavity duplexers. We often send our repeaters off to live in less-than-ideal environments, then expect cavity input/output impedances to remain as we measured them in the shop? Don't think so. IMHO, we're making the same mistake I made in a post the other day, saying VSWR when what we really mean is reflected power as indicated on a meter. Jeff is correct, VSWR along a transmission line doesn't change if source, load and line impedances are stable, the ratio remains the same. What does change, and what is affected by line length, are actual impedances along the line under not-so-perfect-or-stable conditions; the actual impedances along the line change but the ratio does not. For example, 100+j0, 25+j0, 40+j30, and 40-j30, are different impedances yet all exhibit a VSWR of 2:1 in a 50-ohm impedance system. Voltage is proportional to impedance. We can't really have a voltage standing wave ratio greater than 1:1 without a voltage differential, and that really can't happen if impedances along the line remain the same. Our friends at Agilent have put together a Java applet demonstrating what happens along a transmission line. Maybe you're aware of it, it's really kind of cool. The applet allows you to change the load impedance of the model and see the changes, so have fun with it. http://education.tm.agilent.com/index.cgi?CONTENT_ID=6 Our in-line power meters, like our trusted Bird 43, do not directly measure power. They're really voltage meters calibrated in watts at a specific impedance. That's why they can be fooled into displaying an erroneous reflected power reading, perhaps lulling us into a sense of security that the VSWR on the line is acceptable when it may not be. With most transmitters I'm familiar with, a high VSWR condition is detected from a reflected RF sample from a directional coupler at the transmitter's output, so it's not a real VSWR measurement per se, it's a voltage measurement. Worse, these couplers tend not to be very selective, so out-of-channel and even out-of-band energy can cause high VSWR trips even when our measurements indicate all is well on our frequency of interest. Great discussion, keep it going. If I repeated what was already mentioned, my apologies. 73, Russ WB8ZCC _._,___
RE: [Repeater-Builder] Coax length, etc.
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Jeff DePolo Sent: Saturday, August 14, 2010 10:45 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Coax length, etc. Jeff, you aren't stepping on my toes at all. Glad to see your comments. OK, good. Since you've never met me, I can assure you, you definately DO NOT want me stepping on your toes, it would be painful. I do have to agree with Kevin that most duplexer manufacturers recommend different cable length trials between the transmitter and the duplexer when full power can not be reached into the duplexer. Ah, but the crux of the matter is that we're not changing the performance of the duplexer, we're just getting the transmitter to transfer more power into the line. Yes! I fully agree. Over the years I have been a manufacturers rep for TX-RX, Sinclair and Telewave. All of them recommend the same thing. Again, it's a CYA measure as Kevin pointed out. PA won't make power? Don't blame us, try mucking with the cable length, see if that helps. But it is not necessarily the duplexer's problem. I am not a transmitter expert but it is my understanding that the problem is not one of the duplexer not presenting 50 ohms at the wanted frequency but the impedance that it presents off frequency to the transmitter finals. Some solid state devices do not like to see high reactance, even off frequency. But why? If all of the power (or, let's hope, at least 99.99% of it) is on-channel, *should* a properly-designed and properly-functioning transmitter misbehave due to the poor match a duplexer presents at frequencies far removed from the channel center? Well yes, properly designed transmitter. But how much do you want to pay for it? A built in isolator will solve all of those problems as an example. For one thing the reactance causes them to draw more current than normal. Again, why? Not sure why. I have been told by device engineers that is a characteristics of some devices. This may be why you find that tuning for minimum pa current and maximum power out don't exactly agree with one another. I can promise you they almost never do, but that's not any great mystery. You are probably finding a balance between the off frequency reactance and the on frequency wanted load that the finals see. No, that's not it. The off-frequency Z issue is a totally separate topic from the efficiency vs maximum output subject. Let's keep those two topics separate for the sake of this discussion. If what you find in tuning happens directly into a 50 ohm load I agree. If you have the duplexer properly tuned to provide 50 ohms at its input port, the transmitter may still not be happy because of the off frequency reactance presented by the duplexer. I disagree. I would accept the notion that the transmitter may not be happy (and I put that in quotes not to mock you, but becuase I can't come up with a better word either) because it is not *properly matched* when looking into a 50+j0 load. This indicates a deficiency in the amplifier; if it were designed and working right, it *should* make rated power when terminated in a 50 ohm load on-channel. Yes it would be a transmitter problem. Maybe as designed. Changing the cable length in this case really does nothing for the on frequency load between the duplexer and transmitter, when the duplexer is presenting 50 ohms, but it can change the off frequency impedance transformation that the transmitter sees. Yes, but again, I argue that this all points back to a PA problem. Or the input Z of the duplexer really isn't 50 ohms and the line is acting as a transformer. Again I agree. In this instance I was describing a duplexer that did present 50 ohms at the operating frequency and still the transmitter was not happy. Because of the off frequency impedance being transformed to something that the transmitter does not like. It is almost impossible for a high Q cavity to not present some reactance away from the tuned frequency. If it didn't then it would not have any selectivity. The random length cable of course transforms that reactance to something that the transmitter may or may not be comfortable with as discussed above. Detuning the duplexer and or changing cable length to get the transmitter power up is the wrong way to go here. First the transmitter should be optimized into a 50 ohm load. Then optimize the duplexer input for 50 ohms input. Of course I am talking about when the duplexer is presenting a good 50 ohm input impedance at the operating frequency. Yes, yes, yes, amen! Someone asked about a rule of thumb for transmitter to duplexer cable length. There is none! Yes there is. You take out a tape measure and the distance from the transmitter to the duplexer. You make
RE: [Repeater-Builder] Re: Coax length, etc.
Hi Allan, Do we really care what the output impedance of the transmitter is? Most transmitters do not present a pure 50 ohm output but are tuned to transfer maximum power into a 50 ohm load. This often comes out to something way different than a 50 ohm source impedance. As the source impedance does not affect SWR the system doesn't care what it is as long as the transmitter can transfer maximum power into 50 ohms. What the transmitter does sometimes care about is the reflected impedance from the first cavity (being hi Q) that is not on frequency. This presents a highly reactive load to the transmitter that can sometimes cause the transmitter to overheat or reduce output. Placing a cable of a different length between output and the first cavity can sometimes change the unwanted off frequency load seen by the transmitter. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of allan crites Sent: Friday, August 13, 2010 12:56 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Coax length, etc. Nate, I have both the 12th and 14th edition of the ARRL Antenna books, the 12th I acquired in 1974 and have read and re-read the section on transmission lines and impedance matching probabily more than anyone else has. I sometimes learn new things with each re-reading, as there is much to be learned. In my discussions with Kevin Custer about the length of the transmission line connecting the xmtr output and the input to the duplexer, he suggested and I accepted, to colaborate on an article explaining the problems associated with matching the output impedance of a solid state transmitter of somewhat different than the normal 50 Ohms, and the attempts made by a manufacturer of duplexers to adapt (read match) the xmtr output via certain lengths of transmission line and readjustment of the tuning of the cavity closest to the xmtr output to effect this matching, ignoring the possible degradation resulting to the pass and notch characteristics. The transmitter in our discussions was the HB GE Mastr 2 which, in the information available to me, appears to be having an output source impedance of 35+ or - (some unknown) reactance Ohms. Kevin commented that it appears that many hams are unaware of, or understand the methods needed, to do an appropriate job of impedance matching. Therefor we will be making this article for the benefit of those who don't understand the impedance matching necessary for optimum power transfer with a simple to understand way of impedance matching without the use of the infamous Smith Chart (which I have utilized for the past 50 yrs in all my impedance matching solutions and cannot be without). I agree that much information for impedance matching is contained in the ARRL Antenna Book but in my experience, real life adaptation of this information is and can be difficult to many hams. There is also another book I rely on and recommend, which is Electronic Applications of the Smith Chart by Philip Smith. Now, if you would like to contribute to our efforts I would gladly accept your contributions. Thanks for your input. Allan Crites wa9zzu _ From: Sid purvis...@yahoo.com To: Repeater-Builder@yahoogroups.com Sent: Fri, August 13, 2010 10:38:25 AM Subject: [Repeater-Builder] Re: Coax length, etc. I have a note in my file that I do not recall where it came from relative to cable length between the duplexer and the TX or between the duplexer and additional filter. Length = (30)(32.785)(vf/freq). 30 is for 30 degrees, vf is velocity factor, freq is the average of the pass and reject frequencies. If too short add 180 degrees. Don't know if this is good info or not. The article would be appreciated. Sid. --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com , Nate Duehr n...@... wrote: On Aug 5, 2010, at 11:20 AM, Kevin Custer wrote: Allan Crites and I are currently in discussion which will be used as the basis of a RB web article that will explain exactly what is happening, why it happens, and why an 'optimized' cable length can be used to transfer power ending up with the stated loss of the duplexer and have little reflected power toward the transmitter - so long as the duplexer is tuned properly and exhibits good return loss on the frequency it's designed to pass. There's already a great book on that topic, it's called the ARRL Antenna Handbook, and the chapter on transmission lines covers it in more detail than anyone will ever need to know in the real-world, who's not a practicing RF Engineer. That book if read cover-to-cover, is also damn good for insomnia. Or at least it'll keep you distracted while you can't sleep! :-) -- Nate Duehr n...@... facebook.com/denverpilot twitter.com/denverpilot
RE: [Repeater-Builder] Re: how far
It sounds like you have a linear amplifier. Linear amplifiers are used when multiple low power transmitters are to be amplified by one amplifier. The peak power (actually peak envelope power) capability of the amplifier must be quite high in order to handle the multiple signals without generating intermodultion distortion. The peak envelope power increases by the square of the number of signals going into the amp. N^2 * power Example: two 5 watt signals into the amplifier have a peak envelope power of 20 watts. Three have a PEP of 45 watts. Ten 5 watt signals works out to a PEP of 500 watts. (10^2 = 100*5 watts = 500 watts pep) So if you have ten 5 watt transmitters fed into the amplifier the amplifier must be capable of 500 watts PEP. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of George Sent: Sunday, April 25, 2010 4:08 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: how far well this amplifier is rated 90 watts you can see it on e-bay just type powerwave in the search. it has error eliminating computer inside and no distortion what so ever. i have it modified and use it at 450 watts and i pushed it with two power supplys that can put more than 120 ampers at 24 volts. the antenna is rated at 500 watts... i wonder why woud they do that...just to put out 5 watts? --- In Repeater-Builder@yahoogroups.com, Joe k1ike_m...@... wrote: The typical cell site is probably running a 10 watt amplifier with an ERP of about 100 watts. City sites probably a lot less power. Your in the high power paging transmitter class. Physical damage can be done in the nearby horizontal field of the antenna using this much power and antenna gain. Joe On 4/25/2010 3:13 PM, George wrote: what do you mean...a cell site in the city radiates much more times than my antenna, its on the same level and shoots directly in peoples houses... Yahoo! Groups Links
RE: [Repeater-Builder] Re: how far
I am not saying that you are misleading anyone. I am just pointing out to all that the amplifier, if intended for multiple low power transmitter amplification, is indeed capable of rather high power output. 500 watts PEP output with multiple transmitters fed to it is certainly capable of 500 watts carrier output with a single transmitter. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of George Sent: Sunday, April 25, 2010 7:19 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: how far i am using BIRD watt meater with 1000 watt slug and i am not misdirectioning anybody --- In Repeater-Builder@yahoogroups.com, Gary Schafer gascha...@... wrote: It sounds like you have a linear amplifier. Linear amplifiers are used when multiple low power transmitters are to be amplified by one amplifier. The peak power (actually peak envelope power) capability of the amplifier must be quite high in order to handle the multiple signals without generating intermodultion distortion. The peak envelope power increases by the square of the number of signals going into the amp. N^2 * power Example: two 5 watt signals into the amplifier have a peak envelope power of 20 watts. Three have a PEP of 45 watts. Ten 5 watt signals works out to a PEP of 500 watts. (10^2 = 100*5 watts = 500 watts pep) So if you have ten 5 watt transmitters fed into the amplifier the amplifier must be capable of 500 watts PEP. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of George Sent: Sunday, April 25, 2010 4:08 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: how far well this amplifier is rated 90 watts you can see it on e-bay just type powerwave in the search. it has error eliminating computer inside and no distortion what so ever. i have it modified and use it at 450 watts and i pushed it with two power supplys that can put more than 120 ampers at 24 volts. the antenna is rated at 500 watts... i wonder why woud they do that...just to put out 5 watts? --- In Repeater-Builder@yahoogroups.com, Joe k1ike_mail@ wrote: The typical cell site is probably running a 10 watt amplifier with an ERP of about 100 watts. City sites probably a lot less power. Your in the high power paging transmitter class. Physical damage can be done in the nearby horizontal field of the antenna using this much power and antenna gain. Joe On 4/25/2010 3:13 PM, George wrote: what do you mean...a cell site in the city radiates much more times than my antenna, its on the same level and shoots directly in peoples houses... Yahoo! Groups Links Yahoo! Groups Links
RE: [Repeater-Builder] Re: Pager Interference Revisited
Just for grins, find a place (house) to hook your spectrum analyzer up to the local cable system and see if it is on there. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mike Besemer (WM4B) Sent: Saturday, April 24, 2010 6:15 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Pager Interference Revisited Problem is Milt, the darn signal level varies like crazy from day to day and location to location. I can be in a certain spot and receive the signal very well, drive until it disappears, and then have it reappear at a high level as I continue on. Obviously elevation and blockage has a lot to do with that, but it actually does that to the point of being ridiculous. almost like it moves. I have been wondering if one of the pole-mounted CATV amps is going crazy and the stuff is squirting out of the CATV system every place it leaks. Sure wish we'd get a trace of audio (besides the pager) on the darn thing. This is gonna drive us nuts before we're done. I'm hearing the stupid thing in my sleep! 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Milt Sent: Saturday, April 24, 2010 5:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Pager Interference Revisited OK, this is probably not going to be an easy one. I have seen several instances of mast-mounted TV preamps oscillating and acting as miniature transmitters capable of sweeping over wide swaths of spectrum as the temperature changes. They usually exhibit a raw AC buzz on the signal. They are almost never active when the weather is cold, only coming active as the ambient temperature rises. Usually were fed with twin lead. Your description of the audio seems to put that possibility pretty far down the list. At this point I would probably want to look at the incoming signals on the repeater with a spectrum analyser and see if you can quantify the level of the incoming interference signals. If the interference level is high enough you should be able to hear it and maybe track it with a service monitor that can be run off of 12v in a mobile. Since you can call a number on one of the transmitters you can control things a bit. Good luck hunting. Milt - Original Message - From: Mike Besemer (WM4B) mailto:mwbese...@cox.net To: Repeater-Builder@yahoogroups.com Sent: Saturday, April 24, 2010 4:42 PM Subject: RE: [Repeater-Builder] Re: Pager Interference Revisited Milt, Not sure what you mean by 'come and go'. It's there when the pager transmitter is up, gone when it's not. It also comes and goes with heat and sun. we may have days with no interference if it's cool and cloudy or just plain cold. Rain makes no difference. Nothing remarkable about the audio. sounds like clean, clear paging tones. Never heard anything els There is an abundance of TV stations, DTV, translators, AM, FM. you name it. The paging signals are both, depending on which site it's coming from. I can get my hands on pretty much anything I need. Spectrum analyzer is no problem. I have a good 'connection'. Did some hunting with a spectrum analyzer last year to no avail, but now that I have the ability to call the system and have it send out a page we have a little better advantage. I'd call the area 'populated', but not 'urban'. Mostly housing around the site, but plenty of industry (and towers) visible from the top of the water tank. (We are, by the way, the only user on the tank.) From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Milt Sent: Saturday, April 24, 2010 4:19 PM To: Repeater-Builder@yahoogroups.com Subject: e: [Repeater-Builder] Re: Pager Interference Revisited Mike, Does the interfering signal come and go or is it constant? Does it have any AC component; ie buzz or hum at 60Hz, 120Hz, etc., or any raw buzzing noise? Are there any broiadcast TV stations in the area, DTV or LP translators? Is the UHF pager signal analog, digital or both? What test equipmet do you ahve available? Is the repeater in a poplulated area or remote? Milt N3LTQ - Original Message - From: Mike Besemer (WM4B) mailto:mwbese...@cox.net To: Repeater-Builder@yahoogroups.com Sent: Saturday, April 24, 2010 3:36 PM Subject: RE: [Repeater-Builder] Re: Pager Interference Revisited I don't think so, Chuck. I work on Robins and traverse it pretty much from end-to-end daily. I also have to traverse it quite a ways just to get off of it to go foxhunt this beast. Generally the signals on-base are weak to non-existent. It's bloody amazing how much RF crap is in the air. Using a Google Earth application I can see zillions of sites within earshot. The mixing possibilities are endless! I'm
RE: [Repeater-Builder] Sineman/Gary Schafer
Yes I got it, thanks. I never saw one of those that was after my time with helper. -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Dawn Sent: Saturday, March 27, 2010 5:45 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Sineman/Gary Schafer Did you get the e-mail of the Sineman brochure or do I have a wrong e- mail addy?
RE: [Repeater-Builder] Re: Helper Instruments (Voltadder VA 502)
Gary: The guy that marketed that 40 db power pad was actually a rep, a real character. I still have the data sheet and picture somewhere here in my library. He used to tell me his real money came from making and selling waders. BTW I do have the schematic and JPEG of the Cushman 40 db pad with the fuse inside. Should I send it to someone? Ciao, Tony, K3WX 73 Gary K4FMX Hi Tony, That was Don Simons. I think that he is still a rep but last I heard from him he was in Loveland, Co. He even left the rep business for a few years selling his waders. :) 73 Gary K4FMX
RE: [Repeater-Builder] Re: Helper Instruments (Voltadder VA 502)
The idea of the dual meter unit was to be able to quickly go thru a circuit without having to touch the meter to change ranges or change to AC or DC. If you stuck it on a DC circuit it would read that right. If you stuck it on an AC circuit it would read that. Also you could read an AC voltage riding on top of a DC voltage. One meter would display the DC and the other the AC value. Kind of handy sometimes. I may have a catalog sheet of it somewhere around here but I haven't run across it in some time, Yes the mod box was ok but didn't sell to well. The other item I assume that you meant lineman. That was a very slick box and sold well. It was a line level meter with tone generator and audio amp/speaker and mike. It had the commonly used tone remote tones built in so you could check the line level at those frequencies. Usually people bought two of them, one to use on each end of a line being tested. You could talk back and forth to the guy on the other end and send each other tones and measure levels each way. 73 Gary K4FMX There were very few combination analog/DVM's at service instrument prices and the DMM's that had bar graphs didn't have the resoloution for trends at the time. I can only think of a few off hand such as the Keithly,Simpson had an early one in a 260 type case with Nixies,Ballentine $, and Fluke . I think Heath had one for a short time too. I'd love to see a picture of this meter. I'm still trying to grasp what was so special about two separate meters for AC and DC. There had to be some of Bill's magic either comparator presets, audible alarm or some neat thing that would make service easier. While the subject is odd Helper stuff, remember the Mod Box or the Sineman?
RE: [Repeater-Builder] Re: Helper Instruments (Voltadder VA 502)
Ok, I never saw that one. That was after my time with them. There was another small company in Indiana that was started by a couple of ex wavetek guys that build a line test box too. It would fully simulate DC and tone remotes, measure line levels etc. Was a pretty nice box but pricey. I can't remember the name of it now. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Dawn Sent: Friday, March 26, 2010 4:29 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Helper Instruments (Voltadder VA 502) No Gary. I meant Sineman. I'm fully aware of the lineman. That was a bit overpriced for what it did. We had two Nortel units that we bought ex- telco that did the same thing elegantly. The Sineman was a unit that we received a mailed brochure. I'm looking at it now. The description: Microprocessor controlled test set features: AC voltmeter,Sineadder,Line Level meter,Single and DTMF tone decoding and portable battery operation $550 for a short time. The drawing of the unit shows a square box with a large meter and 16 digit keypad on the right. Bridge and terminate switch. 4 controls labeled Mode, Scale,Vol., Level. This doesn't have the typical appearance of Helper products. It looks like a keypad entry version of the Toner 3,Lineman,Sinadder 3 with DTMF decode added. This arrived after Susan took control of the company. I can scan this and upload it if anyone is interested. --- In Repeater-Builder@yahoogroups.com, Gary Schafer gascha...@... wrote: The idea of the dual meter unit was to be able to quickly go thru a circuit without having to touch the meter to change ranges or change to AC or DC. If you stuck it on a DC circuit it would read that right. If you stuck it on an AC circuit it would read that. Also you could read an AC voltage riding on top of a DC voltage. One meter would display the DC and the other the AC value. Kind of handy sometimes. I may have a catalog sheet of it somewhere around here but I haven't run across it in some time, Yes the mod box was ok but didn't sell to well. The other item I assume that you meant lineman. That was a very slick box and sold well. It was a line level meter with tone generator and audio amp/speaker and mike. It had the commonly used tone remote tones built in so you could check the line level at those frequencies. Usually people bought two of them, one to use on each end of a line being tested. You could talk back and forth to the guy on the other end and send each other tones and measure levels each way. 73 Gary K4FMX There were very few combination analog/DVM's at service instrument prices and the DMM's that had bar graphs didn't have the resoloution for trends at the time. I can only think of a few off hand such as the Keithly,Simpson had an early one in a 260 type case with Nixies,Ballentine $, and Fluke . I think Heath had one for a short time too. I'd love to see a picture of this meter. I'm still trying to grasp what was so special about two separate meters for AC and DC. There had to be some of Bill's magic either comparator presets, audible alarm or some neat thing that would make service easier. While the subject is odd Helper stuff, remember the Mod Box or the Sineman? Yahoo! Groups Links
[Repeater-Builder] RE: Helper Instruments (Voltadder VA 502)
That was an auto ranging voltmeter. They were rather expensive at the time, compared to nowadays. As I remember it you could select auto range, or lock it in a particular range. 73 Gary K4FMX -Original Message- From: Alicia Mehrdad [mailto:abcza...@gmail.com] Sent: Wednesday, March 24, 2010 3:26 PM To: gascha...@comcast.net; skipp...@yahoo.com; Repeater- buil...@yahoogroups.com Subject: Helper Instruments (Voltadder VA 502) Hello gentlemen, I found your e-mails on line and I was wondering if you could help me figure out what type of equipment is this, I have a Voltadder Part No. VA 502 from Helper Instruments, it has two windows with a needle meter type and in between the windows it has some lights and number going down. please see example below. -DC + Volts db AC, 500+ 50 150+ 40 50 +30 15 +20 5 +10 1.5 0 db .5-10 .15 -20 . Your help would be greatly appreciated. thank you.
RE: [Repeater-Builder] Re: Helper Instruments (Voltadder VA 502)
Yes he did build some for a few years. They were never a big seller as the price was pretty high. They did work pretty well. It did not have a digital display, only analog meters. There were lights that showed what range it was on. You could read AC on one meter and DC on the other. Handy for some things. I kind of remember him playing around with an attenuator pad to go ahead of a service monitor. I don't remember the wattmeter part though. There was a guy in California making a 40 db power pad to use ahead of a service monitor. It was made during the Singer monitor era to go in front of it. It had a port for the transceiver and one for the signal generator and another for the receive input on the monitor. It worked pretty well. There may be a few floating around yet. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Dawn Sent: Wednesday, March 24, 2010 4:37 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Helper Instruments (Voltadder VA 502) Whoa! Bill actually went through with this? I never seen this as a production item although the idea of a service bench Analog/Digital voltmeter was something he was interested in doing. The DMM's A/D section was to go to an integrator and drive a meter for peaking or nulling. My understanding was this was going to be a service grade instrument with a 3 1/2 autoranging digit DMM basic. Was this a protoype? Are there any pics? While we're at it, what ever happened to the watt meter that fed a power pad like a termaline with an attenuated output? Was that talk, or did they ever do anything with that? --- In Repeater-Builder@yahoogroups.com, Gary Schafer gascha...@... wrote: That was an auto ranging voltmeter. They were rather expensive at the time, compared to nowadays. As I remember it you could select auto range, or lock it in a particular range. 73 Gary K4FMX -Original Message- From: Alicia Mehrdad [mailto:abcza...@...] Sent: Wednesday, March 24, 2010 3:26 PM To: gascha...@...; skipp...@...; Repeater- buil...@yahoogroups.com Subject: Helper Instruments (Voltadder VA 502) Hello gentlemen, I found your e-mails on line and I was wondering if you could help me figure out what type of equipment is this, I have a Voltadder Part No. VA 502 from Helper Instruments, it has two windows with a needle meter type and in between the windows it has some lights and number going down. please see example below. -DC + Volts db AC, 500+ 50 150+ 40 50 +30 15 +20 5 +10 1.5 0 db .5-10 .15 -20 . Your help would be greatly appreciated. thank you. Yahoo! Groups Links
RE: [Repeater-Builder] GAW/Motorola Test equipment
Hi Tony, Yes I remember them! They had some similar products to what Helper Instruments built and Automated Industrial electronics (AIE) run by Tony Crady in North Carolina. AIE later bought out the remains of the Measurements Corp. As I remember GAW did private label some products for Motorola for awhile and may have had their name on them in the Motorola catalog for awhile. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Tony Faiola Sent: Tuesday, March 23, 2010 5:11 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] GAW/Motorola Test equipment From what I remember, Norman Gaw was an ex engineer of the Measurement Corp, Boonton, NJ or one of the other Boonton companies. I still might have some product info in my library (hello Gary Shafer remember them?). Do you need more light? Ciao, Tony, K3WX On Mar 23, 2010, at 4:10 PM, Dawn wrote: Does anyone know what the background of GAW was? There wasn't a shop that I worked in that didn't have one of the Sinad/Distortion analyzers or the two tone generator that also was sold under the Motorola name. IIRC, there was also a small power supply with a hair trigger current trip/disconnect for pagers and handhelds that also was rebadged as a Motorola TEK product. I've heard two stories. One was the Galvin family owned the product line and another was that it was a private venture by an employee and distributed through the Moto network. Can anyone shed any light on this and what other products they made? I don't believe that I've ever seen any of these units sold on E-bay or through private sales although they were pretty ubiquitous. From what I remember, the construction quality was similar to kit grade rather then a professionally assembled product. dwt Yahoo! Groups Links Yahoo! Groups Links
RE: [Repeater-Builder] Re: GAW/Motorola Test equipment
I said North Carolina before but it should have been South Carolina where AIE was located. Yes Batesburg was the city. I think that he worked on a service monitor of his own that never really got off the ground. I don't know if he sold any or not. He later bought out the Singer Instruments service monitor, I think it was an FM100. That didn't go very far either as it was too expensive to build. Same reason Singer abandoned it. Motorola did have a bunch of the GAW two tone generators in their paging plant in Ft.Lauderdale. They also bought a pot load of the AIE two tone generators from me around 1984. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Dawn Sent: Tuesday, March 23, 2010 6:08 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: GAW/Motorola Test equipment Just about the time Detwiller came out with that service monitor (SM- 512) based on a Bearcat BC-210xlt, AIE sent us a flyer introducing a similar product under the Measurements name. From what I remember, it was a rectangular box like a CE-50 and based on a mobile scanner using LED bar graph displays instead of meters. Batesburg, Va. Wasn't it? Never heard anything about them after that. --- In Repeater-Builder@yahoogroups.com, Gary Schafer gascha...@... wrote: Hi Tony, Yes I remember them! They had some similar products to what Helper Instruments built and Automated Industrial electronics (AIE) run by Tony Crady in North Carolina. AIE later bought out the remains of the Measurements Corp. As I remember GAW did private label some products for Motorola for awhile and may have had their name on them in the Motorola catalog for awhile. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Tony Faiola Sent: Tuesday, March 23, 2010 5:11 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] GAW/Motorola Test equipment From what I remember, Norman Gaw was an ex engineer of the Measurement Corp, Boonton, NJ or one of the other Boonton companies. I still might have some product info in my library (hello Gary Shafer remember them?). Do you need more light? Ciao, Tony, K3WX On Mar 23, 2010, at 4:10 PM, Dawn wrote: Does anyone know what the background of GAW was? There wasn't a shop that I worked in that didn't have one of the Sinad/Distortion analyzers or the two tone generator that also was sold under the Motorola name. IIRC, there was also a small power supply with a hair trigger current trip/disconnect for pagers and handhelds that also was rebadged as a Motorola TEK product. I've heard two stories. One was the Galvin family owned the product line and another was that it was a private venture by an employee and distributed through the Moto network. Can anyone shed any light on this and what other products they made? I don't believe that I've ever seen any of these units sold on E-bay or through private sales although they were pretty ubiquitous. From what I remember, the construction quality was similar to kit grade rather then a professionally assembled product. dwt Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links
RE: [Repeater-Builder] Antenna Paint
Marine epoxy paint. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Tim - WD6AWP Sent: Wednesday, March 17, 2010 11:38 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Antenna Paint I picked up a used Telewave antenna ANT150F6-2. It has a minor case of the fiberglass fuzzies and most of the blue paint is gone as it has been in the elements for 15 years. Should I paint it, apply a cote of resin, or just leave it alone? -- Tim, WD6AWP Yahoo! Groups Links
RE: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire
_ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Jack Davis Sent: Wednesday, March 17, 2010 1:15 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire http://groups.yahoo.com/group/Repeater-Builder/message/98899;_ylc=X3oDMTJxM XBnc3YwBF9TAzk3MzU5NzE1BGdycElkAzEwNDE2OARncnBzcElkAzE3MDUwNjMxMDgEbXNnSWQDO Tg4OTkEc2VjA2Rtc2cEc2xrA3Ztc2cEc3RpbWUDMTI2ODgwMDcyMw-- Re: Copper pipe rather than 2/0 copper wire Posted by: Eric Lemmon mailto:wb6...@verizon.net?subject=%20re%3a%20copper%20pipe%20rather%20than% 202%2F0%20copper%20wire wb6...@verizon.net http://profiles.yahoo.com/wb6fly wb6fly Tue Mar 16, 2010 5:55 pm (PDT) Jesse, Not a good idea. Both NFPA 70 (the National Electrical Code) and NFPA 780 (the Lightning Protection Code) have strict requirements for wire sizes and connection methods. Neither grounding systems nor lightning protection systems may use a soldered connection in the circuit. Perhaps your best course of action is to understand the Code requirements, and construct your system accordingly. Keep in mind the fact that your insurance underwriter may deny any and all claims for damages due to lightning, if your system was constructed in a manner inconsistent with the applicable codes. 73, Eric Lemmon WB6FLY You dont need any solder joints with type K or L soft copper. The material comes is 60 or 100 foot rolls and you just flatten the ends and drill holes for mounting bolts and star washers. ½ inch soft copper is actually 5/8 inch OD and makes a great conductor. The material comes in size up to 2 inch but that gets pretty expensive. This pipe is designed to be buried in the ground so you can be assured it will stand up just fine outdoors. One caution is to anchor it down, swinging in the wind will cause it to break due to repeated flexing. All the normal bend radius for electrical conductors should be observed as lightning does not like to make sharp corners. Jack K6YC 5/8 OD gives you 1.96 inches (5/8 x 3.14) of surface area. 1 inch copper strap gives 2 inches of surface area. 2 inch copper strap gives you 4 inches surface area. Copper strap should be less expensive than copper tubing.__,_._,__ Why would you use copper tubing? 73 Gary K4FMX
RE: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of wd8chl Sent: Wednesday, March 17, 2010 1:36 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire On 3/17/2010 12:11 PM, Gary Schafer wrote: 5/8 OD gives you 1.96 inches (5/8 x 3.14) of surface area. 1 inch copper strap gives 2 inches of surface area. 2 inch copper strap gives you 4 inches surface area. Copper strap should be less expensive than copper tubing.__,_._,__ Why would you use copper tubing? Because it's cheaper and a lot easier to find. Many people probably already have some laying around scrap. Hardware stores don't carry copper strap. I know I would have to order it from someone like Tessco or someone else that sells tower site supplies. A quick google search turns up this: http://www.dxengineering.com/Products.asp?ID=102SecID=51DeptID=19 2 inch strap for $1.83 per foot. Someone earlier said that 1/2 inch copper pipe cost around $2.20 per foot. If 1/2 inch pipe is really 5/8 inch outside diameter that would give you a surface area, as I said before, of 1.96 inches. 2 inch copper strap would give you a surface area of 4 inches. Better than twice the surface area of the pipe and less money. To get the same surface area with pipe as with copper strap you would have to pay about $4.50 per foot for pipe verses $1.96 for strap. Doesn't look cheaper to me. 73 Gary K4FMX
RE: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire
Here is another place to get copper strap even cheaper: http://www.gacopper.com/ $1.05 per foot for 2 inch strap. (.012 thickness) $1.70 per foot for 2 inch strap. (.022 thickness) 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Gary Schafer Sent: Wednesday, March 17, 2010 3:39 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of wd8chl Sent: Wednesday, March 17, 2010 1:36 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire On 3/17/2010 12:11 PM, Gary Schafer wrote: 5/8 OD gives you 1.96 inches (5/8 x 3.14) of surface area. 1 inch copper strap gives 2 inches of surface area. 2 inch copper strap gives you 4 inches surface area. Copper strap should be less expensive than copper tubing.__,_._,__ Why would you use copper tubing? Because it's cheaper and a lot easier to find. Many people probably already have some laying around scrap. Hardware stores don't carry copper strap. I know I would have to order it from someone like Tessco or someone else that sells tower site supplies. A quick google search turns up this: http://www.dxengineering.com/Products.asp?ID=102SecID=51DeptID=19 2 inch strap for $1.83 per foot. Someone earlier said that 1/2 inch copper pipe cost around $2.20 per foot. If 1/2 inch pipe is really 5/8 inch outside diameter that would give you a surface area, as I said before, of 1.96 inches. 2 inch copper strap would give you a surface area of 4 inches. Better than twice the surface area of the pipe and less money. To get the same surface area with pipe as with copper strap you would have to pay about $4.50 per foot for pipe verses $1.96 for strap. Doesn't look cheaper to me. 73 Gary K4FMX Yahoo! Groups Links
RE: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire
The math is right. RF will not flow on the inside of a tube. It acts as a waveguide beyond cutoff. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kirk Mefford Sent: Wednesday, March 17, 2010 4:49 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire Not that I think copper pipe is a good alternative to strap, but Gary's math is slightly off. If you are saying 2 inch strap has 4 inches of surface area by counting both sides of the strap, then you need to count both sides of the pipe. Inside and outside surfaces of a pipe equal to 5/8OD would be very close to the same surface area of a 2 inch strap of the same thickness. Might be ok for grounding a temporary setup or for ground radials on an HF antenna but I wouldn't want to gamble on insurance covering a station using flattened copper pipe as a grounding solution. - Original Message - From: Gary Schafer mailto:gascha...@comcast.net To: Repeater-Builder@yahoogroups.com Sent: Wednesday, March 17, 2010 11:11 AM Subject: RE: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Jack Davis Sent: Wednesday, March 17, 2010 1:15 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire http://groups.yahoo.com/group/Repeater-Builder/message/98899;_ylc=X3oDMTJxM XBnc3YwBF9TAzk3MzU5NzE1BGdycElkAzEwNDE2OARncnBzcElkAzE3MDUwNjMxMDgEbXNnSWQDO Tg4OTkEc2VjA2Rtc2cEc2xrA3Ztc2cEc3RpbWUDMTI2ODgwMDcyMw-- Re: Copper pipe rather than 2/0 copper wire Posted by: Eric Lemmon mailto:wb6...@verizon.net%20 wb6...@verizon.net http://profiles.yahoo.com/wb6fly wb6fly Tue Mar 16, 2010 5:55 pm (PDT) Jesse, Not a good idea. Both NFPA 70 (the National Electrical Code) and NFPA 780 (the Lightning Protection Code) have strict requirements for wire sizes and connection methods. Neither grounding systems nor lightning protection systems may use a soldered connection in the circuit. Perhaps your best course of action is to understand the Code requirements, and construct your system accordingly. Keep in mind the fact that your insurance underwriter may deny any and all claims for damages due to lightning, if your system was constructed in a manner inconsistent with the applicable codes. 73, Eric Lemmon WB6FLY You dont need any solder joints with type K or L soft copper. The material comes is 60 or 100 foot rolls and you just flatten the ends and drill holes for mounting bolts and star washers. ½ inch soft copper is actually 5/8 inch OD and makes a great conductor. The material comes in size up to 2 inch but that gets pretty expensive. This pipe is designed to be buried in the ground so you can be assured it will stand up just fine outdoors. One caution is to anchor it down, swinging in the wind will cause it to break due to repeated flexing. All the normal bend radius for electrical conductors should be observed as lightning does not like to make sharp corners. Jack K6YC
RE: [Repeater-Builder] Copper pipe rather than 2/0 copper wire
Copper strap is better as you get the benefit of both sides of the copper. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Jesse Lloyd Sent: Tuesday, March 16, 2010 11:42 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Copper pipe rather than 2/0 copper wire Hey All, I am thinking about lightening protection for a site and using 1/2 copper pipe runs rather than a heavy guage wire like 2/0. 1/2 copper is about $2.20 a ft, while 2/0 is about $3/foot... and 2/0's diameter is about 0.36 inches so bang for the buck 1/2 copper pipe seems the way to go. I know skin effect plays a big role in lightening since its mainly RF, what do you think about the idea? Cheers, Jesse Yahoo! Groups Links
RE: [Repeater-Builder] Copper pipe rather than 2/0 copper wire
3 wide copper strap gives you 6 of surface area. ½ pipe gives you 1.57 surface area. So even 1 strap provides more surface area than ½ pipe. I think that you will find it less expensive than pipe and with the added benefit of not having to splice it every 10 feet. ¾ pipe gives you 2.355 surface area. The inside area of pipe does not count. RF will not flow on the inside of a tube/pipe. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of David Jordan Sent: Tuesday, March 16, 2010 12:18 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Copper pipe rather than 2/0 copper wire Strap meaning solid copper, not copper or silver tinned braid. However, one might argue that the copper tubing has an equal amount of surface area and is more robust than the thin copper strap being sold.. if you fold 3 wide copper strap into a piece of tubing you get a ¾ OD tube. So, does the inside surface count? If not then the strap is the clear winner with double the surface area. What a hoot, Dave Wa3gin _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Gary Schafer Sent: Tuesday, March 16, 2010 11:59 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Copper pipe rather than 2/0 copper wire Copper strap is better as you get the benefit of both sides of the copper. 73 Gary K4FMX
RE: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
This is a resend of my email to Nate last night. It looks like good old yahoo stripped my reply. Hi Nate, A UHF pass band cavity for example will pass only a UHF frequency that it is tuned for. On frequency signals coming into it will see 50 ohms. Off frequency signals will see a short circuit and will be greatly attenuated. The input loop of the cavity (as well as the output loop) looks like a short circuit at all but the tuned frequency. So anything that happens to be in parallel with the loop will also see the short circuit if the frequency is not that to which the cavity is tuned to. So if you had a half wave length cable between the cavity and your T connector, then the short circuit at the cavity (off frequency short) would also look like a short circuit at the T connector. No problem for the UHF signal as that frequency sees 50 ohms at the T. but any other frequency sees a short circuit at the T and would be attenuated there. Now if that cable was a quarter wave length instead of a half wave length, the short circuit (off frequency short) would be transformed to an open circuit at the T connector. That would allow all other frequencies to be present with no attenuation at the T. If you used a random length of cable here, you may be ok and you may not be depending on how far away from a quarter wave length the cable happened to be. This is exactly how a duplexer works. The cables between the T and each cavity set is a quarter wave length at the opposite frequency for which the cavity is tuned to. The quarter wave length cable connected to the T always wants to see a short at the other end at the frequency that it does not want to pass, as the quarter wave length transforms the short to a open which does not load down the other side of the circuit.. With close spaced duplexers sometimes the two cables may be very close in length or the same, as the cable is not near as high a Q as the cavity is. Further to your current post, there is more of a chance of hitting a bad cable length than there is of not. Only a quarter wave length will transform short (low impedance) to a high impedance to the T. All other lengths will be something with lower impedance at the T, which you don't want. If everything is set up right you should be able to remove the other cable from the T and notice no difference on the remaining receiver. As far as passive splitters go rather than using the above cavity setup, it is always a good idea to use a splitter for isolation between receivers. The same thing can happen as described above (with no cavities) as the tuned input stage on the receiver will do the same thing to rob power from the other receiver depending on cable length between a T and the receivers. A splitter really does not rob any power from the system. If you think about it, each receiver is going to pull half of the power from the antenna line anyway. So just the fact that you connected the two together, the total antenna power is going to be shared between the two receivers if you are lucky enough to not have other losses due to impedance match problems sucking more than that out. So the 3 db loss that a splitter gives you is there anyway. But with the splitter everything sees the proper impedance and maximum power is transferred to each. UNUSED PORTS ON A RECEIVER MULTICOUPLER A receiver multicoupler by the way is basically just a multi way splitter. A TV splitter is built exactly the same. There are two different type of couplers used. One type the unused ports must be terminated in order to maintain 50 ohms at all other ports. The other type it doesn't matter if they are terminated or not as the port on this type is isolated by the amount of port to port isolation. Depends on the manufacturer. VSWR LOSSES ON RECEIVER ANTENNA LINE Yes you can have vswr losses on your receiver line going up the tower depending on the match that the line sees down at the BOTTOM of the tower. It works just the opposite of a transmitter line. The transmitter line requires a good match at the antenna end of the line in order to keep the vswr low on the line. This will keep lose to a minimum. But when the energy is originating at the antenna end of the line, then the match at the bottom of the line becomes important to minimize vswr loss on the line. A mismatch at the bottom of the line causes reflections (with part of the received power) to go back up the line and become attenuated by the regular line loss. At the top of the line that energy is re-reflected back down the line again and is further attenuated by the regular line loss. This re-reflected energy eventually adds to the signal (minus the amount lost). So the worse the match the more reflected energy there is going back and forth on the line and less ultimately reaches the receiver. The more original line loss there is the worse the problem becomes. This is another reason for paying attention to proper matching at the receive end. You end up with the
RE: [Repeater-Builder] Dual receivers on one antenna for RX only site
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of wd8chl Sent: Tuesday, March 09, 2010 11:07 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Dual receivers on one antenna for RX only site It you are not combining the UHF and VHF signals with cavities then a signal splitter should be used. Even a TV cable type splitter will work ok for this. Don't worry about it being 75 ohms rather than 50 ohms. Without a splitter one receiver can load the input of the other considerably (depending on the luck of cable lengths) if just a simple T is used to connect the antenna to the two receivers. I know of a system that has 2 VHF receivers tied to one antenna with a 'T' connector and random coax-deliberately. At the T junction, the receivers need *many* uV of signal...plus the squelch is all the way tight. Too many problems with out-of-town junk on the input. So it has many rx's and a big voter. It proves your point-if you just use a 'T' connector, it'll be deaf as a doorknob. In this case the receivers would benefit from a splitter. That would make everything see 50 ohms regardless of cable lengths. Also the splitter 3 db loss per side will probably be less that what it is now as each receiver takes half the power to start with no matter if you have a splitter or not. 73 Gary K4FMX
RE: [Repeater-Builder] Antenna Phasing Question
As far as phasing the antennas around the tower, it can't be done. Well it can but you will end up with more nulls and a worse pattern than you started with. The problem is that most signals will arrive at more than one antenna. Because they are different distances apart to the mobile there will be a time difference between the two. So you say ok, I will just make the phasing harness that same length as the antennas are apart. That would work great for one specific direction. But what happens when that mobile moves to a new azimuth location? Then there will not be the same distance to him between the two antennas as there was when you made the phasing harness. Now you have a new time difference between arriving signals but you have the same length phasing lines. The result is that the combined signals are no longer in phase so you have less gain. If the two signals fall out of phase then they will cancel. You have a big null in the pattern there. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of afa5tp Sent: Wednesday, March 10, 2010 12:31 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Antenna Phasing Question Hello Folks I have three (3) Antel [BCD 80010] 806-900 mHz vertical antennae that I would like to mount on the three legs of my tower for omni pattern (Rec. only). Several questions come to mind. 1.) At the rated frequency, how many inches should the side arm place the ant. from the tower? 2.)What would be the best way to phase the antennae? I have a Andrews three port Splitter, and will use LDF4-50A for feedline. I would suspect the length of the pigtail from each antenna to splitter is going to be critical...or not, for receive only? BTW..How good of an antenna is the Antel BCD 80010? Many thanks for any guidance and wisdom. Tim Hardy W7TRH/AFA0TP Vashon Is. Wa. Yahoo! Groups Links
RE: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
Well yes the T is sort of a magical device that makes the OTHER SIDE of the T disappear electrically. Actually it is not the T itself that does the job (that is just where IT happens) but it is the quarter wave length cables that perform the magic! Without the quarter wave length cables between the T and each set of cavities the duplexer would not work! That is what provides the 50 ohm isolation between tx and rx cans so the feed line still sees 50 ohms. The quarter wave cable effectively disconnects the transmitter from the feed line at the T (at the receive frequency). The quarter wave cable on the receive side of the T effectively disconnects the receive side from the feed line (at the transmit frequency). Without doing this each would load the other down and there would not be 50 ohms at the antenna port of the T. Once you are on the other side of the T (the antenna port) the feed line length has no effect on the duplexer operation. All that the quarter wave lines do on the duplexer side of the T are to give isolation to the opposite side (tx-rx) so each does not short out the feed line. A similar thing happens between can cables in a duplexer but rather than using them for isolation they are used to enhance the notch of each can by presenting a high impedance at each cans T from the previous cavity. Working with a high impedance is easier to notch out than a low impedance. The notch in the first cavity presents a short (low impedance) at the unwanted frequency and 50 ohms at the wanted frequency. By coupling the next cavity with a quarter wave length cable (at the unwanted frequency) that short is transformed to a quite high impedance at the next cavity while at the same time the wanted signal being at 50 ohms is passed to the next cavity where it sees 50 ohms and goes on its way unatenuated. But we are left with the high impedance at the unwanted frequency that was transformed by the quarter wave cable. The second cavity notch is also tuned to the unwanted frequency which it pulls down to a short (low impedance) to give further attenuation. When I say the notch presents a short it is not really a short but a very low impedance of say a few ohms. But by having the unwanted source impedance high rather than at 50 ohms it is much easier to pull the high impedance down with the few ohms short circuit than it would be if we were working at 50 ohms for the unwanted. It works like a voltage divider between the two impedances. The higher the source is (from previous cavity) to the short the more loss there will be which is just what we are looking for. In the case of the quarter wave cable to the T on the output of the duplexer we want to transform the low impedance up to a very high impedance at the T so that it does not load the circuit at that point on that frequency. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Dan Hancock Sent: Wednesday, March 10, 2010 12:50 PM To: repeater builders Subject: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site One thing was missed regarding cable lengths. The loops in the cans are part of the equation for figuring the 1/4 wave length. I've seen that discussed here many times in postings related to inter-cable lengths on duplexers. But the 1/4 wave length issue only applies to the inter-cabling between the cans. It is my understanding that the antenna to duplexer lengths are irrelevant since the T connector and the rest of the feedline are all part of the equation. It's not like the T is some magical device that makes the rest of the feedline disappear electrically. The only time length might be a problem is if the entire feedline happens to be a resonant length. If by some chance that happens, then changing the jumper a couple of inches will clear that. Dan N8DJP Posted by: n...@no6b.com http://us.mc1104.mail.yahoo.com/mc/compose?to=n...@no6b.com n...@no6b.com http://us.mc1104.mail.yahoo.com/mc/compose?to=n...@no6b.com no6b Date: Tue Mar 9, 2010 8:29 pm ((PST)) At 3/9/2010 20:12, you wrote: OK, question... If you put a cable which is 1/4-wavelength at VHF between the T and the UHF cavity, it's 3/4-wavelength at UHF. Since any odd multiple of a quarter wavelength will invert the impedance, what will this really accomplish on the UHF cavity side? Doesn't matter at UHF, since the cavity looks like (hopefully something close to) 50 + j0 ohms @ UHF, so the cable length has no effect (other than plain ol' cable loss) @ UHF. At VHF, the short at the UHF cavity connector (I'll take Gary's word that it looks like a short off-resonance, though to be sure you'd want to put the can on a VNA to get the actual phase angle at the connector) needs to be transformed to an open at the T so it has no effect VHF. The short-to-open transformation @ VHF is accomplished with a 1/4 wavelength of coax @ VHF. The
RE: [Repeater-Builder] Dual receivers on one antenna for RX only site
Quarter wave length cables are the thing to use to couple the cavities together at the antenna connection side of them. The uhf cavity gets a cable that is a quarter wave length at the VHF frequency and the VHF cavity gets a cable that is a quarter wave length at the UHF frequency. These connect to a T connector at the antenna line. This is the same way that you connect TX and RX cavities of a duplexer to an antenna. The UHF cavity loop provides a short circuit at the VHF frequency but the quarter wave cable from it transforms the short to an open (high impedance) at the T connection so you get no attenuation of the VHF signal there. The VHF signal then passes to the VHF cavity as if the UHF cavity was not there. The same thing happens to the UHF signal going to the other cavity. Without the proper length cables between the cavities and the antenna T connector both UHF and VHF signals will be attenuated depending on the luck of the cable length. The quarter wave length cable is the electrical length. It you are not combining the UHF and VHF signals with cavities then a signal splitter should be used. Even a TV cable type splitter will work ok for this. Don't worry about it being 75 ohms rather than 50 ohms. Without a splitter one receiver can load the input of the other considerably (depending on the luck of cable lengths) if just a simple T is used to connect the antenna to the two receivers. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Nate Duehr Sent: Tuesday, March 09, 2010 5:11 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Dual receivers on one antenna for RX only site Answers below On 3/9/2010 8:29 AM, Ross Johnson wrote: Can a dualband antenna VHF/UHF for RX ONLY be fed to two receivers one VHF, one UHF, without a quote duplexer using a T instead? Yes. Typically performance is better with mono-band antennas, since all multiband antennas are a trade off in their design, but a T, or even splitting multiple times is certainly an option for any receive-only antenna system, with the caveat that there's loss at each split. Pre-amplifiers can help a bit, but once an RF signal is lost, there's no getting it back by amplification. Here's the idea. This is a remote RX site. The idea is to run something like a beefed up X500 dualbander at tower top, then 7/8 hardline 100 feet down to the receivers. So far fine. Both receivers will have one or two bandpass cavities inline before the T. I assume when you say before the T you mean antenna - split - bandpass - receiver. Yes, this is probably a good idea to keep the receiver from being hammered by other signals that are out-of-band, but not 100% necessary if this receive antenna is out in the middle of nowhere with no high-power transmitters nearby. The bandpass filtering is lossy too, of course. The higher the Q of the bandpass filter, the less the loss. (High Q bandpass cavities are typically MUCH larger than BpBr duplexer cans. At VHF they're enormous and take up a lot of space. Ceiling mounts are common.) remember also that you're really only adding the bandpass to design for what the receivers NEED to have filtered to perform at their best. If the receivers are something like the GE MASTR II or similar with a cavity helical filter front-end (bandpass filter) built-in, you don't NECESSARILY need more filtering in front of them. Just sayin'. Design your filters specifically for your receiver's ability to handle out-of-band or nearby signals and the signals that you expect to be present at the site. The filtering has nothing to do with the multi-bandedness of the antenna, etc. UNLESS your chosen receiver is particularly bad when say, a 1/4 KW 900 MHz transmitter is 2 feet away from the receive antenna, and your particular radio doesn't like that. (An example I saw once... even WITH filtering the amount of 900 MHz energy coming through the filters was enough to piss off a UHF receiver, being it was a 2x multiple of the UHF's front end and passed through without much loss. Would a duplexer be necessary in this case. Or could it be done with proper cable lengths and a T? A duplexer is a set of filters designed to pass a transmit frequency and filter it out of a receiver on a nearby frequency. Did you mean diplexer? I think that's what you're really meaning to ask. And the answer is no... you don't truly need a diplexer. ESPECIALLY if you're running separate bandpass filters on each receiver. Think about what a diplexer does... it passes lower frequencies to one port, and higher frequencies to another port... if you're already going to bandpass filter there's no need for it. As far as cable lengths go, I have no idea what you're asking. Cable lengths should have no effect on this system at all. Thanks for your time and for the probably obvious answer I'm not sure of.
RE: [Repeater-Builder] Dual receivers on one antenna for RX only site
_ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Nate Duehr Sent: Tuesday, March 09, 2010 7:24 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Dual receivers on one antenna for RX only site On 3/9/2010 4:53 PM, Gary Schafer wrote: Without the proper length cables between the cavities and the antenna T connector both UHF and VHF signals will be attenuated depending on the luck of the cable length. What technical reason causes this? Nate Hi Nate, A UHF pass band cavity for example will pass only a UHF frequency that it is tuned for. On frequency signals coming into it will see 50 ohms. Off frequency signals will see a short circuit and will be greatly attenuated. The input loop of the cavity (as well as the output loop) looks like a short circuit at all but the tuned frequency. So anything that happens to be in parallel with the loop will also see the short circuit if the frequency is not that to which the cavity is tuned to. So if you had a half wave length cable between the cavity and your T connector, then the short circuit at the cavity (off frequency short) would also look like a short circuit at the T connector. No problem for the UHF signal as that frequency sees 50 ohms at the T. but any other frequency sees a short circuit at the T and would be attenuated there. Now if that cable was a quarter wave length instead of a half wave length, the short circuit (off frequency short) would be transformed to an open circuit at the T connector. That would allow all other frequencies to be present with no attenuation at the T. If you used a random length of cable here, you may be ok and you may not be depending on how far away from a quarter wave length the cable happened to be. This is exactly how a duplexer works. The cables between the T and each cavity set is a quarter wave length at the opposite frequency for which the cavity is tuned to. The quarter wave length cable connected to the T always wants to see a short at the other end at the frequency that it does not want to pass, as the quarter wave length transforms the short to a open which does not load down the other side of the circuit.. With close spaced duplexers sometimes the two cables may be very close in length or the same as the cable is not near as high a Q as the cavity is. 73 Gary K4FMX
RE: [Repeater-Builder] Motorola cabinet key wanted
Ok, thanks to all that replied. It looks like it is a 2553 that I need. Looking at the chart it looks like the CH751 is for the old outdoor cabinet and the 2553 is for the indoor cabinet. Also looks like the GE cabinet that I have is probably the desk mate and takes the LL201 key. Ted, K9MDM sent me an email saying that he has those keys for sale. I will probably get them from him. Thanks again to all Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Bill Hudson Sent: Wednesday, February 24, 2010 1:51 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Motorola cabinet key wanted This is what you saw - and this is what you are looking for: http://www.repeater-builder.com/keyspage/keyspage-index.html Bill Hudson W6CBS Ex-Motorola 1983 _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of ka9qjg Sent: Tuesday, February 23, 2010 10:35 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Motorola cabinet key wanted Let Me tell You youngsters out here How bad Memory loss is , as Some of us get older I could swear that on this group or one I use Someone Posted a File about KEYS But for the life of Me I cannot find it , It listed Everything . And I have searched for 2 hours trying to help but did not find it. Oh well just wait Some of you will catch up soon , My favorite saying is that it's Great as We get Older to learn something New every day it is remembering it is the problem PS Please tell Me that I am not just making this up Happy Repeater Building Don KA9QJG
RE: [Repeater-Builder] Motorola cabinet key wanted
Hi Bill, Well now I am having second thoughts! The Motorola cabinets that I have are older than the Motrac era. I can't recall the model of the radios but the finals in one are 100TH tubes. That was before the motrac. The cabinets are at my farm in Wisconsin so I can't run out and look at them for a few months. They are not the black wrinkle paint finish. They have 3 or 4 simpson meters on the top outside. On the GE cabinet I am not sure what vintage that is. The key list that you referred to shows the LL201 being for some GE desk mates and also the BF10A for later ones I assume. Thanks! Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Bill Hudson Sent: Wednesday, February 24, 2010 5:30 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Motorola cabinet key wanted OK - you are getting closer. Yes, from your original description of the Motorola cabinet, the 2553 is correct. It is the Micor / Motrac era. Yes, the CH751 is the large beige upright cabinet with a handle on it. Motrac era. NO, if it is truly a GE DESKMATE cabinet, it will take a BF10a key. While the documentation I referred you to discusses LL201 for a deskmate cabinet, I have never seen an LL201 work on a deskmate cabinet. The deskmate was during the progress line era. LL201, is for what was known as pre progress line. Just for fun, I tried an LL201 in a GE DESKMATE cabinet, and it would not work. I'm sure there is an exception somewhere in the world. I have just about every key for all radios including EF Johnson. I hate getting locked out of radios and cabinets. Ha ha Bill Hudson W6CBS _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Gary Schafer Sent: Wednesday, February 24, 2010 1:16 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Motorola cabinet key wanted Ok, thanks to all that replied. It looks like it is a 2553 that I need. Looking at the chart it looks like the CH751 is for the old outdoor cabinet and the 2553 is for the indoor cabinet. Also looks like the GE cabinet that I have is probably the desk mate and takes the LL201 key. Ted, K9MDM sent me an email saying that he has those keys for sale. I will probably get them from him. Thanks again to all Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Bill Hudson Sent: Wednesday, February 24, 2010 1:51 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Motorola cabinet key wanted This is what you saw - and this is what you are looking for: http://www.repeater http://www.repeater-builder.com/keyspage/keyspage-index.html -builder.com/keyspage/keyspage-index.html Bill Hudson W6CBS Ex-Motorola 1983 _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of ka9qjg Sent: Tuesday, February 23, 2010 10:35 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Motorola cabinet key wanted Let Me tell You youngsters out here How bad Memory loss is , as Some of us get older I could swear that on this group or one I use Someone Posted a File about KEYS But for the life of Me I cannot find it , It listed Everything . And I have searched for 2 hours trying to help but did not find it. Oh well just wait Some of you will catch up soon , My favorite saying is that it's Great as We get Older to learn something New every day it is remembering it is the problem PS Please tell Me that I am not just making this up Happy Repeater Building Don KA9QJG
RE: [Repeater-Builder] Re: Can the 4th harmonic of 1250 AM keep UHF repeaters locked up?
Don't be too sure about that. Once the am station signal gets into the receiver it can go anywhere and cause havoc. It could be getting into the IF or the mixer once picked up by cables. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of KT9AC Sent: Wednesday, February 24, 2010 4:42 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Can the 4th harmonic of 1250 AM keep UHF repeaters locked up? If it was just audio then there would be no feedback of the PL/DPL tones, keeping the repeater locked up. Good advice though. Jeff DePolo wrote: On 2/23/2010 3:11 PM, Jim WB5OXQ inb Waco, TX wrote: Is it possible the AM signal is getting into an audio stage instead of the receiver front end? I had that happen once. Same here. All audio inteconnects are now tiny coax cables at that site now, installed with shield grounded at ONE end... Nate WY0X At AM broadcast sites or studios co-located with the transmitter, hard-grounding the shield at one end and RF-coupling the shield at the other end to the equipment ground via caps (0.01 uF as a rule of thumb) is often the most effective technique in many situations. --- Jeff WN3A Yahoo! Groups Links
[Repeater-Builder] Motorola cabinet key wanted
I am in need of a cabinet key for an old Motorola base station cabinet. It is an old low band 1/4 kw rig. Had 100TH tubes in final. This is the 6 foot tall cabinet. Anyone know the key number for these? Have a key? Also have an old GE progress line base cabinet that needs a key. This cabinet is about 3 feet tall and longer than wide. Thanks! Gary K4FMX
RE: [Repeater-Builder] Motorola cabinet key wanted
Hi Bill, The key is like a 2135 and a 2135 will fit in the lock (I have a 2135) but it will not open it. I actually have two of these station cabinets and my 2135 key will not open either cabinet. I kind of remember that some of the cabinets had a different key from the mobiles way back when. Any other guesses? Thanks Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Bill Hudson Sent: Tuesday, February 23, 2010 10:37 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Motorola cabinet key wanted Just because I gamble a little - I'm going to bet that the older Motorola cabinet is a CH751. This is a one sided key unlike a 2135. The Micor cabinets became a 2553. Cabinet Keys more prominent in the high power stations. I'll go along with the BF10a for the Prog Line - that's for sure. Bill Hudson W6CBS _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Andrew Seybold Sent: Tuesday, February 23, 2010 6:18 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Motorola cabinet key wanted The Motorola key should be a 2135 and the GE Key is probably a BF10A, they are hard to find but around-I can make you copies if you want to pay the key making price and postage. Andy W6AMS From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Gary Schafer Sent: Tuesday, February 23, 2010 6:16 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Motorola cabinet key wanted I am in need of a cabinet key for an old Motorola base station cabinet. It is an old low band 1/4 kw rig. Had 100TH tubes in final. This is the 6 foot tall cabinet. Anyone know the key number for these? Have a key? Also have an old GE progress line base cabinet that needs a key. This cabinet is about 3 feet tall and longer than wide. Thanks! Gary K4FMX
RE: [Repeater-Builder] Re: DB-201 Measurements for 6 Meters?
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Kris Kirby Sent: Monday, February 22, 2010 5:03 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: DB-201 Measurements for 6 Meters? On Mon, 22 Feb 2010, Jeff DePolo wrote: On Mon, 22 Feb 2010, Jeff DePolo wrote: Kinda along the same lines as always make the cable from the connector on the transmitter to the connector on the duplexer an even half-wave. The reason for doing that is that if the duplexer presents a short-circuit, said short-circuit won't appear at antenna port. Uwhat? I was thinking quarter-waves. If you have a tee, connect the antenna at the center and a duplexer to either side using quarter-wave cables, the effect I noted should occur, minimizing losses. -- Kris Kirby, KE4AHR Disinformation Analyst Well, at the output side of the duplexer that is what is happening already. The cables are a quarter wave length. The one from the transmit cans (to the antenna port) is a quarter wave length at the receive frequency and the one from the receive can (to the antenna port) is a quarter wave length at the transmit frequency. Since the receive can is tuned to the receive frequency, its output loop presents a short circuit to the transmit frequency. And since the cable going from that loop to the antenna T is a quarter wave length at the transmit frequency that short at the loop is seen as a very high impedance to the transmit frequency at the antenna T. The same thing happens on the transmit side of the affair but on the other frequency. That's how you get separation between the transmitter and receiver at the T junction. However, what Jeff was talking about was the cable between the TRANSMITTER and the duplexer input. His comment was tongue in cheek to make his point about the antenna. That cable in most cases can be any random length. There are times when a selected length will help the transmitter with the load that it sees due to out of band impedances that get presented to it. But you can not say that a certain length will be called for. 73 Gary K4FMX
RE: [Repeater-Builder] Re: battery
Paul has some good points about batteries. Here are a few more: A so called marine deep cycle/starting battery is nothing more than a little heavier starting battery. A true deep cycle battery has much larger plates than a starting battery. A starting battery has thinner plates which allows it to release energy faster than batteries with thick plates. The thin plate batteries can release very high currents in a short time but too much and it will warp the plates. A true deep cycle battery with heavy plates can not supply current as fast as a regular battery but it can be discharged to a lower point without harm. A regular starting battery should not be discharged below around 80% and should be immediately recharged after the draw down. A deep cycle battery should not be discharged below 50% and should be immediately recharged after use. Every discharge will shorten the life a battery. Leaving it in the discharged state for a few days is sure death of the battery. Proper charging of batteries needs to be controlled. Too much charging current will warp the plates just like too much discharge current and ruin the battery. Batteries need to be overcharged a little so that there is some gassing or they will never reach full charge. Batteries also need to be floated at the proper voltage to maintain their life. 13.6 volts is about right for most deep cycle batteries and some regular automotive types. It depends on the material used in the plates. In most cases 13.8 float voltage will kill these batteries over time. A tenth of a volt or so is critical with the float voltage. AGM batteries require a different float voltage. Ask the manufacturer what it should be. A battery that is designed to be floated at 13.6 volts will never reach full charge at 13.6 volts after a discharge. It will take at least 14 volts to charge it properly with current limiting. There are a lot of old 13.8 volt chargers out there that have been around for years. These were used a lot on boats. They were big heavy beasts that could supply lots of current when needed. Most were the fero-resonant regulated type. 13.8 was a compromise between charge and float voltage. They are responsible for more battery sales than any other cause. 13.8 will not fully charge the battery but at the same time it will allow it to gas and boil off the water over time which exposes the plates and kills the battery. If the batteries were floated at 13.6 they would last a long time but will not fully charge at this voltage unless they were first charged at a higher voltage. Just because you have a 140 AH battery doesn't mean that you can draw that much power from it in an hour. That is usually a 10 or 20 hour ratting. That means that you could draw 14 amp from it for 10 hours. Then it would be dead. Since you don't want to go below 50% for a deep cycle battery that means that it would only last around 5 hours. Note that a 10 hour verses a 20 hour curve is different. You can't just half or double one to get the other. They are not linear. The 10.5 volt rate for a dead battery is with no load. A starting battery will drop down to 7 or 8 volts sometimes under starter load. It all depends upon the internal resistance of the battery. As they get old the internal resistance goes up as the plates become sulfated and they are not able to supply as much current without a large voltage drop. Think of it this way: If you need large amounts of current for a short time then a regular starting battery is best. If you need moderate amounts of current for a long time then a deep cycle battery is what to use. Find out what the recommended discharge rate is for the batteries that you are going to use for backup and match that against the current draw of your equipment. You can't just arbitrarily throw batteries in and expect good results. AGM batteries are not all they are cracked up to be. They are really just a regular flooded cell type battery but with a gel rather than liquid electrolyte. They have matting to hold the gel to the plates. Some may have a different plate material makeup. The big advantage is the no vent requirement. The best bang for the buck in deep cycle batteries are gulf cart batteries. Usually they come as 6 volt batteries. They are very tough, can withstand lots of vibration and abuse. Very good life if properly managed. You do need to vent liquid filled batteries to outside air. On boats when the batteries are mounted in the engine compartment they have natural venting from engine air vents. You don't want them in a sealed box. Placing these type batteries in an equipment cabinet may be fine for a long time as long as they are just being floated. But when the equipment goes down and a heavy draw is place on the batteries they will gas. Also during charging they will gas, sometimes heavily. If there is not much air movement for the gas to escape the cabinet an arc from a relay can set it off. Same reason that you always want to turn off a
RE: [Repeater-Builder] Re: The GLB Preselector- Preamplifier
It comes down to where are the IM products really being generated. I think what Skipp is trying to say is that if the preamp generates spurious products from overload that fall outside of the center frequency, that filtering behind the preamp will help keep those products out of the receiver. While this may be true, keep in mind that any IM products that are generated by the preamp are going to be at fairly low levels because of the inefficiency of the mixing action in the preamp. A mixer is what it becomes when you get into the non linear range of the preamp. But as with any mixer its product amplitude is going to be way down from the signals that cause the mixing. The off frequency products generated by a non linear preamp are not the real problem. It is the on frequency products that get thru. They are going to be relatively weak also but because they are on frequency everything in the chain is going to amplify them. Filtering at the output of the preamp will do nothing to reduce any mixing action in the preamp as that is dependent on input level. Measuring 3rd order products is done at the output of the device so with filters at the output it is going to look like the filters are helping reduce these off frequency products but that is not how you measure IM performance of a device. They are usually referenced to on frequency levels. Also keep in mind when reading IM specs for an amplifier that some manufacturers reference to the input and some reference to the output of the amplifier. Referencing to the output makes the spec look better by the amount of gain that the amp has. Adding filters to the output of the device can help reduce the IM tendencies in the following receiver however by keeping off frequency signals out of the receiver. It is the total amount of power that reaches a device that causes overload. But any off frequency IM products that may be generated in the preamp will be much weaker than direct off frequency signals So the addition of filters after the preamp may seem like they help the preamp but they are really helping the receiver from generating IM in its first active stage. Remember that when you add a preamp you destroy the IM performance of the receiver by the amount of gain in the preamp. 73 Gary K4FMX Letting the preamp generate poop then filtering the off-channel garbage you've already generated in that preamp is a poor solution; Ah, now were getting close... now assume the preamplifier generates really bad unwanted products in extremely overloaded conditions that don't occur most of the time. When the buckshot flies for relatively modest times... the trailing internal/external filters (regardless of location) would help a good receiver better deal with the event. the in-band garbage generated in the preamp goes right on through. And now we ask how much F-center and close adjacent in band garbage actually gets to the receiver front-end and how well do the receiver(s) handle this event? With the right hardware layout a lot better than you might assume at first glance.
RE: [Repeater-Builder] Re: pre-amp placement
Most of the time you will want as much selectivity as you can get in front of the preamp. The only time that I can think of off hand where you might want a filter behind a preamp is if you are getting a receiver feed from a receiver multicoupler that has a preamp in it, giving a few megs wide signal out of the multicoupler. Overload of a preamp depends on the total amount of power that gets into it. The wider the window in front of it the more total power that has potential for getting in from many other transmitters. This can cause IM products to be generated in the preamp itself. Once that happens you have opened the barn door and there is not much you can do after the preamp to help the receiver. Sometimes if is good to use a preamp that doesn't necessarily have the best noise figure but maybe has a higher dynamic range (higher intercept point) if your site has lots of nearby transmitters and noise that could overload the preamp. Having a very low noise figure doesn't do you any good if the preamp causes IM to be generated. The second thing is not to run too much gain in the preamp so that the added gain overloads the front end of the receiver. For every Db of gain the preamp provides that reduces the receivers IM rejection ability by the same number of Db. So again if you have lots of strong adjacent signals at your site you don't want lots of preamp gain. Total receiver system noise figure is partially set by the preamp if its noise figure is lower than that of the receiver, which it usually is. Using a preamp with a .5 Db noise figure and a receiver with an 8 Db noise figure won't give you a total noise figure of .5 Db, but somewhere in-between. The more gain the preamp has the lower the overall noise figure will be in this case, unless you have enough gain to cause some of the other low noise figure stages in the receiver to go into compression as Mel eludes to. The stage that goes into compression in the receiver doesn't necessarily have to be the front end of the receiver. The first IF stages in most receivers have a pretty low noise figure and help establish the overall noise figure of the receiver as well as the front end of the receiver. So these stages can be overloaded with too much gain and cause a noise figure reduction. But the biggest problem with too much preamp gain is overloading the mixer in the receiver and causing it to generate IM products. By controlling the gain of the preamp (using attenuators after the preamp) or by other means you can usually find a happy medium of some gain to improve system noise figure (sensitivity) and not too much gain to destroy the IM performance of the receiver. One way to do that is to put in attenuation until the sensitivity just starts to degrade with the preamp in the circuit. That will give you good sensitivity and good IM performance. Any more gain and all you are doing is degrading the receiver IM performance. When shopping for preamps don't only look at gain figures and noise figures, also look at the intercept point to see how much signal it will handle before compression starts. That's where it will start generating IM products. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Mel Swanberg Sent: Thursday, November 26, 2009 12:40 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: pre-amp placement You might need to add a several DB attenuator between the pre amp and the receiver to keep from over driving the front end. Not if you use a good receiver, or not use a preamp with too much gain. Bob NO6B What defines too much gain can vary wildly. One trick I learned in building transverters for the microwave bands, and one I now apply to VHF/UHF preamps is to check the overall noise figure of the system as a whole. You'd be surprised at what just a few db too much gain can do, and it doesn't necessarily show up with a quick sensitivity check. A preamp can be placed in front of a receiver and, yeah, now the receiver is more sensitive. But if it's a .5 DB NF preamp, and you're not careful, your system noise figure can end up going from, say, 6 db for the barefoot receiver, to 4 db with the preamp - an improvement to be sure, but not nearly as good as the preamp may be capable of. If that preamp is driving the receiver front end even just a little bit into compression, you've lost a lot of potential. Even with a good receiver. Carefully balancing preamp gain with attenuation on the output can be extremely useful. Not everyone has a noise figure meter, though, and measuring NF on an FM receiver is a pain in the neck. A sinadder can be used to the same effect, even if the actual noise figure isn't known. It can be interesting to observe insertion of a few db of pad between the preamp and a receiver, and watch the sinad sensitivity of a receiver improve by a few
RE: [Repeater-Builder] Best coax for marine use
You certainly don't want just any old coax. You for sure don't want any type of hard line run up the mast as the flexing will break the center conductor or outer conductor. You want to have a stranded cable such as RG8 type. Also don't use any type of foam dielectric type cable on a boat as the center conductor will migrate to the shield and short the cable especially at places where the cable bends. Polyethylene center insulator is best for this application. Even though foam has slightly lower loss, the low loss doesn't do you any good if the cable fails. Inside a sailboat mast there is no way to secure the cable and it will flop around inside the mast. Lots of stress on the cable. As a side note, there should be NO solid conductor wires used on any boat. Only stranded wires due to the constant movement and related stress. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Vernon Densler Sent: Tuesday, November 24, 2009 11:18 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Best coax for marine use I have been in a big discussion with the guys on my boat list about the right coax for running up the mast for VHF marine radio. Keeping in mind that we are talking about a 70' or so run going up the center of an aluminum mast, in a salt water environment, and the radio is limited to 25 watts. Also keep in mind that when off shore this is a life line and the best possible send and receive is needed in an emergency situation. So given the criteria what is the best possible coax to use knowing that thickness matters and bend radiuses may be tight? Others on the list are saying just grab any old 8X type cable and you will be fine. I say use something with very low loss and suggested small heliax. Any suggestions? Vern s/v Nirvelli KI4ONW
RE: [Repeater-Builder] Has anyone measured out-of-band rejection for a duplexer?
You can make the measurement with a signal generator and a tunable receiver that has some kind of indicator for signal strength. It doesn't even need to be calibrated. Connect the signal generator to the antenna port and the receiver to the receiver port of the duplexer. Be sure to disable the transmitter. Find a reference level with the signal generator on the operate frequency. Then tune the signal generator to the interested rejection frequency and find it with the receiver. Then note the signal generator level and increase its output to match the receive strength that you noted at the start. The difference between the two levels is the amount of rejection the filters are giving you at the frequency of interest. With a pass/reject duplexer you won't have a lot of off frequency rejection as there is not much of a pass band on that type of duplexer. There will be good pass band rejection in the space between tx and rx frequencies due to the overlap of the filter skirts but outside of either it is not much. For an added receiver filter, your pass/notch filters again will not do too much for you as far as pass band rejection goes. If you use them to reject a specific frequency, each can should give you about 30 db of notch rejection but you may have some degradation of the wanted frequency if it is far removed. And you will probably not be able to move the notch far enough such as the broadcast band. You may be able to convert the cans to pass cavities by changing the coupling loops. Then you can do the same measurement as described above to see how much rejection you will get. Also look at some pass band curves in the catalogs and you will see about how much rejection a pass cavity will give you at a given distance away from where it is tuned. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Tony KT9AC Sent: Monday, November 23, 2009 1:36 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Has anyone measured out-of-band rejection for a duplexer? Hi Everyone, Without the benefit of a spectrum analyzer, I would like to find out how much rejection of out-of-band signals can be expected from a typical UHF duplexer. Have a MSF5000 on 452 that works fine with the T4084 duplexers (1500 style), but have a lot of VHF data and FM broadcast hash that is trying to make it in (the 45kW FM is about 400 yards away and the VHF data is almost 1/3 harmonic). Looking at the documentation, I can guess its about 20db per cavity (or can), but the graphs don't extend very far. So for a regular four-can duplexer I might be providing 40db of protection. I want to increase this, and plan on adding one or two more cans on the receive side, and a Sinclair preselector in-between the latter two to make up for the increased insertion loss. Just wondering if anyone ever tried/measured this, or had ideas about filtering out FM broadcast. Eric mentioned using a single 7 Sinclair cavity, but I'd like to see if I can use some spare 1500 bandpass/reject cavities first. I don't think a 1/4-wave stub will work with that much field strength prying open the MSF's front-end. Thanks, Tony Yahoo! Groups Links
RE: [Repeater-Builder] Re: 2 dB Error in DVM level readings
I don't have a 189 but have other fluke meters. Measuring in dBm, to measure an absolute value, you must first know what load you are measuring across. Then the meter must be set up to read zero dBm across that load impedance. One of the fluke meters that I have has several different settings of load resistance references so that it will read absolute dBm correctly. If you just want to read relative dB between two different levels then the load impedance is not important. Just stick the meter on the load with the signal applied and read the reference level in dBm (or offset the zero at that level) then change the level of the signal and read the dB difference between the two. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of skipp025 Sent: Friday, November 20, 2009 2:38 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: 2 dB Error in DVM level readings So we all (here) pulled out our meters for a comparison. First off... our one Fluke 189 does measure in dBm as did every meter and transmission test set in the shop. So all is not glitters that is written in technical forum stone (gold). s. skipp025 skipp...@... wrote: Pasted from another Technical Forum This comes up from time to timewell, it came up again. Check the display for the measurement unit. Fluke 189s measure in dBV (dB referenced to one Volt), not dBm (dB referenced to one milliWatt). 0dBm (.775 VAC) is a couple dB different in voltage from 1 Volt. A good clue is on the display of the 189 over to the right, it says dB and V. When the 189 is measuring a 0 dBm tone, it indicates -2.21 dB V and the small voltage display indicates .775. If you use the old 20 log (.775/1) formula, you come up with a difference of -2.21 dB. All of the DVMs are high impedance input, so they don't measure actual power. The 189s only know that 1VAC is displayed as 0dBV and the 287s know that .775 VAC is displayed as 0dBm when it is in the dBm mode. Those of you who have the new 287s get to read dBm directly and as an added bonus, get to change batteries very frequently. Those of you who have the 189s get to use your smarts more and don't have to change batteries so often. Check the specs on your individual DVM. It may be able to count CTCSS. The old wideband AC Voltmeters are failing rapidly. You will have to use your Transmission Test Set and possibly some functionality of your DVM to replace the greatness of the old wideband AC Voltmeter. Yahoo! Groups Links
RE: [Repeater-Builder] ACSSB
Agreed Rob. ACSSB is nothing more than regular old SSB with a few things added. The compandering is simply speech compression on the transmit end and an equivalent expansion on the receive end to restore the dynamic range of the voice. This gives some noise reduction in the circuit. As mentioned before the SEA radios placed the pilot tone in the middle of the band pass. The other guys just inserted some carrier (as I remember) for a pilot. This has been done for many years in the marine radio service on the SSB circuits. The carrier was run at 20 db down from peak power. The repeaters were licensed with a specific ERP and height above average terrain. So combiner loss, cable loss, antenna gain and height above average terrain were all factored in to determine the power output of the repeaters. The biggest problem was the cost of the equipment. They could not get the cost down to be competitive with FM. ACSB started out on the VHF bands with a few channels placed in-between FM two way channels. The problem there was too much interference from the FM side bands that clobbered the ACSSB receivers. Being amplitude based there is no capture or limiting like there is with FM so any little noise is heard. ACSSB can have much better range than FM with a clear channel (no noise) but it is hard to find such. SEA petitioned the FCC for a portion of the 220 band to get ACSSB only channels to get away from the problems with sharing with FM on the VHF channels. It was a good thought but the equipment had other problems, mostly manufacturing at reasonable cost. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Robert Pease Sent: Friday, November 13, 2009 8:01 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] ACSSB Interesting thing about part 97. It is written differently than any other part of the rules. In most of the rules they tell you what you can do and if it isn't specifically spelled out then you can't do it. In part 97 it is the other way around. For the most part they tell you what you can't do. So unless it specifically says you can't so it, it is assumed ok. This was done this way to promote experimentation with new modes and new ways to use old modes. I can't speak to this mode specifically but look at it technically as in bandwidth, modulation,... The tech specs that may exclude it from use, not the name or mode itself. JMO. YMMV. Rob Sent by Good Messaging (www.good.com) -Original Message- From: DCFluX [mailto:dcf...@gmail.com] Sent: Thursday, November 12, 2009 09:13 PM Eastern Standard Time To: Repeater-Builder@yahoogroups.com Subject:Re: [Repeater-Builder] ACSSB Could you please provide a rule number to back this up? Linear Modulation and ACSSB share 4K00J3E as the emission designator. On Thu, Nov 12, 2009 at 5:34 AM, n0fpe n0...@cox.net wrote: One thing to remember. Amatuers are NOT authorized to use ACSSB above 30mhz. Please check part 97 for the exact modes we are able to use. heck if we were there would be tons of ACSSB repeaters already modified into the ham band. (Yahoo! ID required) Change settings via email: Switch mailto:repeater-builder-dig...@yahoogroups.com?subject=email%20delivery:%20 Digest delivery to Daily Digest | Switch mailto:repeater-builder-fullfeatu...@yahoogroups.com?subject=change%20deliv ery%20Format:%20Fully%20Featured to Fully Featured Visit http://groups.yahoo.com/group/Repeater-Builder;_ylc=X3oDMTJjdGcyZDNmBF9TAzk 3NDc2NTkwBGdycElkAzEwNDE2OARncnBzcElkAzE3MDUwNjMxMDgEc2VjA2Z0cgRzbGsDaHBmBHN 0aW1lAzEyNTgxMTcyMjE- Your Group | Yahoo! Groups http://docs.yahoo.com/info/terms/ Terms of Use | Unsubscribe mailto:repeater-builder-unsubscr...@yahoogroups.com?subject=unsubscribe
RE: [Repeater-Builder] isolation
Absolutely you need some reserve. The same if you are designing a point to point path. You don't select equipment that will just do the job. You always need a certain amount of reserve for changes of equipment etc. the idea is that some think the repeater is going to work better with more isolation in the duplexer just because it has more isolation. Once you meet the isolation requirement and some reserve built in to cover things that drift etc., then more is not going to help you. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Sunday, August 23, 2009 8:45 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] isolation I agree with Kevin. You need a little headroom built in for conditions that could change. Equipment ages and changes it's operating characteristics. Temperature swings cause the same issues. Does one need to go overboard? Probably not. But if you happen to be right on the edge under perfect conditions, you may be unhappy when something moves a bit out of tolerance. Chuck WB2EDV - Original Message - From: Kevin Custer mailto:kug...@kuggie.com To: Repeater-Builder@yahoogroups.com Sent: Sunday, August 23, 2009 9:30 AM Subject: Re: [Repeater-Builder] isolation Gary wrote: Dan Kagabine, the chief engineer at TX-RX systems use to always say that once you have enough isolation to overcome any desense, then any more is a waste of money as it does nothing for you. If you only need 70 db then a 100 db duplexer does nothing more for you than a 70 db duplexer. While I'll agree that more isolation, then what is needed to insure no desense is a waste; if this gentleman is suggesting that isolation in reserve is a waste, I strongly disagree. Why? Operating conditions can change - snow and especially ice on the repeater antenna can detune the system and isolation in reserve will allow the repeater to operate without desense until the reserve is used up. Kevin Custer
RE: Re: [Repeater-Builder] Diversity FM reception
The reason FM stations transmit circular polarization is to accommodate both horizontal and vertical receive antennas. Most fixed receivers are horizontal and most cars are vertical. You can not transmit both horizontal and vertical polarization at the same time. Feeding a horizontal antenna and a vertical in phase will give 45 degree polarization. For simultaneous vertical and horizontal the antennas must be fed as circular. They then contain both the horizontal and vertical component. They are not doing this for the sake of circular polarization but only so vertical and horizontal polarizations can be transmitted together. TV has no need to transmit anything other than horizontal polarization as most TV reception is done with a horizontal antenna. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of John Sehring Sent: Sunday, August 23, 2009 12:51 AM To: Repeater-Builder@yahoogroups.com Subject: Fw: Re: [Repeater-Builder] Diversity FM reception I turn out that use of CP in urban suburban areas results in somewhat more signal strength on linearly polarized antennas, e.g. vertical whips on cars straight rod aerials on portable FM radios. Due to preferential scattering of vertically polarized sigs from typical urban structures, there tends to be more of that available, esp. good for auto FM reception. The Germans for example are more concerned with signal quality than quantity so don't use CP. However, there is a drawback: there's more multipath. So the tradeoff was made--more signal strength but at lesser quality (due to multipath distortion). Well designed FM radios reduce separation intelligently in the presence of multipath: first they gradually blend the stereo channels into mono, high audio frequencies L-R info first, then all audio (L+R) is gradually lowpass filtered. This happens dynamically, on the fly. Works well IMO when done properly. TV broadcasters tried CP as well but couldn't live the extra multipath: it was easily visible as more ghosting. See for example: http://www.ham-radio.com/k6sti/ for more on this. --John --- On Fri, 8/21/09, larynl2 lar...@hotmail.com wrote: From: larynl2 lar...@hotmail.com Subject: Fw: Re: [Repeater-Builder] Diversity FM reception To: Repeater-Builder@yahoogroups.com Date: Friday, August 21, 2009, 9:08 PM In reference to below, what would be the real advantage to using CP antennas in addition to the V and H you'd have already? Any signal that arrives will excite a V and/or H antenna according to it's arriving polarization, and I don't see where CP would be a help. Most FM broadcasters use CP. Those that don't are licensed for only V or H or choose to use a less-expensive single-polarization antenna. And many of them look like rototillers, and other shapes. Laryn K8TVZ --- In Repeater-Builder@ yahoogroups.. com, John Sehring wb...@... wrote: There's more to be done with polarization as well: Circular, both RH LH. It is possibile to make omnidirectional CP antennas. FM broadcasters use a lot of them. They look like a bunch of arrows.
RE: [Repeater-Builder] isolation
Dan Kagabine, the chief engineer at TX-RX systems use to always say that once you have enough isolation to overcome any desense, then any more is a waste of money as it does nothing for you. If you only need 70 db then a 100 db duplexer does nothing more for you than a 70 db duplexer. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin Custer Sent: Saturday, August 22, 2009 5:38 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] isolation Eric, You may have missed the point. While your program calculated a necessary isolation amount of 99.65 dB, using a GE M2 PLL exciter would dictate 77.65 dB of necessary isolation - which is easily obtainable with a quality 4 cavity (okay, 4 large cavity) duplexer. While I certainly wouldn't recommend a duplexer using four 5 cavities, a four cavity duplexer utilizing 8 inch cavities would provide more than adequate isolation (90+ dB of isolation) for this gentleman's arrangement. If he were using a multiplier exciter (which the 'program' assumed), then one can certainly understand your recommendation - but - he did say PLL exciter and M2 equipment. I'm not sure I understand your statement Nothing about duplexers is for certain. All of the duplexers I have ever tuned came out to factory specifications or better. If not, something was physically wrong - lightning damage - cabling problems - loop problems, etc. I don't believe that if this person were to utilize a quality four cavity duplexer that we'd be setting him up for failure. Engineering is on our side, and he can benefit from not needing to spend extra money for something that isn't really necessary. BTW: It is possible to duplex a PLL exciter (200 mW) and M2 receiver (no preamp) at 600 kHz with nothing more than a tee connector. You do have to skew the helical tuning a bit so the skirt is sharp on the side of the transmitter; which reduces receive sensitivity to less than factory specification. I won't say there will be zero desense, but you won't even get close with a multiplier exciter in the same test. It's fun - tastes great - less filling! Kevin Kevin, Nothing about duplexers is for certain. While I agree that a PLL exciter is inherently less noisy than its multiplier counterpart, I never assume that it's okay to plan ahead for less than optimum isolation. Some duplexer designs are known to have better performance than physically identical designs from other manufacturers- the silver-plated copper cans from Decibel Products are one example. I feel that it's better to have a duplexer that is perfectly tuned and has absolutely zero desense, than a lower-performance duplexer that has only a little desense. In an ideal world, KJ4SI should be able to buy a four-cavity BpBr duplexer and try it out for 30 days to see if it had zero desense- with the option to purchase two more cans and the appropriate jumpers at a discount for upgrading it to a six-cavity duplexer. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin Custer Sent: Saturday, August 22, 2009 12:52 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] isolation Eric, Are you sure about your six-cavity recommendation? The MASTR II PLL exciter has 22 dB less side-band noise than a typical multiplier exciter - using 600 kHz TX to RX separation. Assuming his preamp isn't driven into a non-linear region (it shouldn't be), a good 4 cavity duplexer, like a WACOM WP-641, should give plenty of isolation... Kevin Custer My CommShop calculates 99.65 dB is required. I'd definitely be looking at a six-cavity BpBr duplexer for this station. 73, Eric Lemmon WB6FLY -- Hope someone may have a program,commshop? What I need to know is what amount of isolation with duplexers that is required for a GE m2 receiver with .1...@12db and a m2 pll exciter,100 watt PA on vhf,600kc split?1/2in helix,with 4pole db224 antenna at 70 ft. thanks kj4si
RE: [Repeater-Builder] Isolator vs intermod panel?
Definitions: Circulator - ferrite device with 3 ports. Isolator - Circulator with a load on the 3rd port. Intermod panel - Isolator with a harmonic filter. The harmonic filter may consist of a 2nd harmonic notch filter or a low pass filter or a band pass cavity. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Paul Kelley N1BUG Sent: Monday, July 20, 2009 6:16 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Isolator vs intermod panel? I guess I was lucky in my first few years as a repeater owner. Lately I have nothing but grief in many forms. (Yeah I know, welcome to the real world!) Can someone tell me in basic terms what is the difference between an isolator and an intermod suppression panel which contains an isolator? If one has a high power tube PA on a repeater, I assume he would need to use a high power isolator or intermod panel after the PA? Or would it be sufficient to use a lower power one between the solid state exciter and tube PA? Thanks... Paul N1BUG Yahoo! Groups Links
RE: [Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode
Actually galvanized and copper plated ground rods should not be mixed in any ground system. Electrolysis will deplete the plating. All ground rods in any ground system are electrically connected to one another. 73 Gary k4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Glenn Little WB4UIV Sent: Tuesday, June 30, 2009 7:53 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode Another way to pass a ground cable through concrete is via a PVC pipe. The last thing that you want to do is run a ground cable that can carry lightning fault current through concrete without isolating the cable from the concrete. The fault current will rapidly heat the ground cable, causing it to expand, at the same time vaporizing the water trapped in the concrete. The result is a violent steam explosion. The results could be the total fragmentation of the concrete. MIL HDBK 419 is available for download. This is a military manual that addresses grounding. Another very respected guide is Motorola R-56. Galvanized ground rods should only be used at the guy anchor points. Copper plated ground rods should be used around the tower base and the building with all bonded together by exothermic welds 18 inches below grade. Ground rods are to be placed no closer than twice the length of the rod. Any closer and you are wasting your funds. YMMV. 73 Glenn WB4UIV At 10:07 AM 6/30/2009, you wrote: I'm going to disagree with the following posting: If the tower is bolted to galvanized pipe that is embedded in concrete of which a significant amount is in contact with soil, you have a concrete-encased grounding electrode which is hard to improve upon. It is not likely that a ground rod would be worthwhile, since damp concrete (concrete in intimate contact with soil at grade level) is a fairly good conductor, and such a footing or foundation has hundreds of times the surface area of a ground rod. I have read Ericsson specs for cellular tower installation in that disagrees with the previous statement. Standard concrete without conductive enhancing materials can crack, pop or crumble if subjected to a direct lightning strike if ground rods are not properly installed. The water contained within the concrete will vaporize instantly causing the concrete to fail. There are types of conductive concrete mixes or additives that can be used, but the most common practice is to use a ground rod from each leg with a copper wire bonded to each tower leg. Our mfg building at work is made from steel I-Beams into concrete. I have noticed each I-Beam has its own ground connection. The strap is bolted to the beam about 1 above the concrete, then disappears into the concrete, and suspect there is a ground rod going into the soil beneath the concrete piling, but thats just a theory, as I dident see it before the mud was poured. Ed N3SDO
RE: [Repeater-Builder] DC Ground Lightning Protection on antenna????
Some lightning facts: There is no amount of grounding that will help protect an antenna from lightning damage. Grounding will not help an antenna or tower from being struck by lightning. However if a lightning rod is placed above the antenna or a wire sloping down from above and around the antenna it will intercept a lightning strike and prevent the antenna from being hit. It would be important to have the lightning rod/wire well bonded to the tower and the tower well grounded. A well grounded tower and antenna bonded well to the tower will help prevent damage to other equipment tied to the antenna. Also feedlines should be well bonded to the tower at top and bottom. Ground rod surface area is much less important than length. Extra surface area contributes little to rod effectiveness. Too long of a ground rod and the extra length becomes ineffective due to the high inductance of the long length. Several ground rods spaced approximately the sum of the length of two adjacent rods is most effective. A good lightning ground consist of a low impedance, low resistance and high capacitance coupling to earth. Lightning is composed of very low (DC) and high frequencies (peak at around 1 MHz). If many ground rods are used in a star configuration, it is not necessary to use large wire connecting all the rods as the lightning energy will be divided between all paths so less current flows on any individual wire. If ground rods are placed in a star configuration it does no good to add rings of wire connecting the rods together. The lightning energy travels in a straight line out away from the tower on each radial and each radial carries equal current. So there is no difference of potential between rods or radials. Copper strap for ground connections will reduce the inductance thus lowering the impedance of the path. A separate heavy copper wire or strap running down a tower tied to the antenna to ground is a waste of copper. The tower itself is a much lower inductance path than what a separate ground wire provides. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Eric Lemmon Sent: Monday, June 29, 2009 7:42 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] DC Ground Lightning Protection on antenna If the tower is bolted to galvanized pipe that is embedded in concrete of which a significant amount is in contact with soil, you have a concrete-encased grounding electrode which is hard to improve upon. It is not likely that a ground rod would be worthwhile, since damp concrete (concrete in intimate contact with soil at grade level) is a fairly good conductor, and such a footing or foundation has hundreds of times the surface area of a ground rod. Just be certain that your station equipment is solidly bonded to the tower and to the electrical service neutral with a #6 AWG or larger copper conductor. Specific guidance for the grounding and bonding of radio and television antennas, including Amateur Radio systems, is found in Article 810 of NFPA 70, the National Electrical Code. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of agrimm0034 Sent: Sunday, June 28, 2009 9:34 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] DC Ground Lightning Protection on antenna I bought a nice looking RFS Celwave antenna to use on 462.600 Specs are DC ground for lightning protection but is there something I need to do to make sure it is protected? It sits on 3 legged tower 40 ft up and the tower is mounted on the side of a structure. It sets on 3 pieces of galvanized pipe that are set in concrete. Overall the tower is grounded just not as good as what I could make it be. If I ran a grounding rod into the ground and ran #8 or heavier wire to the tower would I just be wasting my time to protect the antenna or what should I do to make sure everything is protected ok. Thanks Yahoo! Groups Links
RE: [Repeater-Builder] Re: Desense on High Power Linear Repeater?
Receiver gain does not work the same as transmitter power increase. A 10 db increase in transmitter power is not the equivalent of adding a 10 db preamp on the receiver. It would be if your receiver was very noisy (internally)(very poor receiver) to start with and the 10 db preamp overcame the receiver noise by that amount. But that rarely is the case. With a good receiver to start with you may gain only a couple of db realization on the receiver when adding 10 db or more gain ahead of it. You may not realize any increase in signal recovery if there is a high noise level at the site. Also for every db of gain that you add in front of the receiver you decrease the intermod performance of the receiver by the same amount. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Kris Kirby Sent: Wednesday, May 20, 2009 9:03 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Desense on High Power Linear Repeater? On Thu, 21 May 2009, atms169 wrote: Yes, 80 dB on the duplexers, 100 watts in, that's 10 dB and the preamp 18 dB, so I'm losing 8 dB ?? Assuming you're not experiencing front-end overload because of your pre-amp. The sensitivity I believe is 0.4 uV Dstar system. I live in Texas where it's flat. I'm adjusting my station to compensate for the height value. More power good receive. There is a 1000 foot commercial tower here which would have been perfect, but they want too much to let me use it. Yeah, they tend to charge quite a bit to get to the top of a 1kft tower. I had thought of adding two more cans and purchasing a new phasing harness but, someone told me to stop and just add more filters. So I'm not sure which direction to go. I would like to push more power if possible. Transmit power does not equal recieve capability. You have to think bi-directionally. If you have a 6dBd antenna, and a mobile has a 3dBd antenna (unlikely these days), then transmitting 5W is equivalent to the mobile transmitting 10W. However, reciever sensitivity plays an important part as well. If you can't hear a station who is running 50W into a 3dBd antenna, he likely is not in a position to hear your repeater at 25W into a 6dBd antenna. Again, take out the pre-amp, insert a silver-plated teflon barrell. -- Kris Kirby, KE4AHR Disinformation Analyst Yahoo! Groups Links
RE: [Repeater-Builder] Re: Isolator Loss
Do you have a low pass filter after the isolator? 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of offtrack Sent: Saturday, May 16, 2009 11:19 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Isolator Loss Eric Thanks for the confirmation on this. Its an older one that was tuned for me its a T-2200 that was replaced by the T-1530 I think, if I read correctly at the telwave site. I notice that the TKR 750 is running fine with no intermod issues ect. I was not sure about adding that meter in line and only did a quick check. Thanks for the warning on that one. The Diamond is so far working ok. I soldered all the parts in the antenna and sealed up all the possible leak points with a compound call through the roof This stuff stays semi flexible and is clear. Its located at my home and has been in service for about 2 years for my Simplex Echolink node I replaced with the repeater. Works pretty good, but that said I would never put it on a remote site as your correct not at all heavy duty. the radome is egg shell thin, I worry about it at the house as I am on a hill and get hit with some good winds/icing. So the Isolator in line helps ease my mind a bit. Thanks KB7DZR Scott --- In Repeater-Builder@yahoogroups.com, Eric Lemmon wb6...@... wrote: Scott, I must assume that you purchased a Telewave T-1530 Isolator, and its specified insertion loss is 0.4 dB. The readings you took indicate that the isolator is working properly. However, it is not a good idea to insert a meter between the isolator and the dummy load. The correct operation of the isolator depends upon a stable 50 ohm impedance at the dummy load port. I think you made some good choices for the duplexer, feedline, and isolator. The Diamond F22 is perhaps not the most rugged antenna for 2m repeater use, but YMMV. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of offtrack Sent: Friday, May 15, 2009 7:27 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Isolator Loss Hi all, Thanks for the group it has helped me out a bunch. My system here is a Kenwood TRK K2 and Telewave TPRD-1556 6 can set. Feed line is Heliax LDF4-50A about 70 feet and the antenna is a Diamond F22 that has been worked over and sealed up better. The system is new and today I added a Telewave Isolator to the PA output before the duplexer TX input. With my meter I got about 28 watts out of antenna side of the duplexer set when connected to my antenna with out the isolator. With the Isolator I am getting about 26 watts out now. This seems good to me but I am new to an Isolator. Putting the meter between the isolator and the dummy load it is showing around 1.6 watts going to the dummy load. Just want to see if this is ok for this? KB7DZR Scott Yahoo! Groups Links
RE: [Repeater-Builder] Interference or Intermod ( ? ) Help....here goes
First I would completely remove the external amplifier and connect the repeater directly to the duplexer. Then turn the power up to where it belongs on the transmitter. Sounds like the transmitter is generating a spur. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Michael Ryan Sent: Thursday, February 26, 2009 12:51 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Interference or Intermod ( ? ) Helphere goes My recent efforts at putting a 220 repeater on the air here in western Florida have been mildly succesful. I am using a Neutec designed repeater. ( I know there are some uhf and vhf models around, this one is on 220, a RANGER brand ). The repeater is open access. And runs quiet all day or night, nothing cracking the squelch at all. But during times when there is a conversation going on after a few minutes a rather nasty signal captures the repeater sometimes in short bursts, sometimes much longer. Sounds like someone talking into a reverb chamber.. I had been using a Mirage brick amp in the rack, but suspected that this amp might be the problem, some oscillation or internal mixing of some sort. This turned out not to be the case, the amp though still in the circuit is OFF but we still get the garbage. When the amp would be ON, and I would sometimes hear this stuff start, and I could turn OFF the amp an it would stop. But shortly later even with the amp OFF, it is back.very odd that it would appear to me. Now, all cables in the rack are RG-400. Every one in the rack. Half inch hardline runs to the antenna, though there is a splice with a double male N connector as I recall. The Neutec unit does about 25 watts output but I have it cut back to about 10 watts thinking it will run cooler. Thus with the small brick amp it was doing about 65 watts output to the Telewave 4 cavity duplexer. While at the site tonight, I could hear something getting into the recvr. The repeater was UP, but no one talking at that moment. Again, nothing on it's own ever appears to break the squelch. The noise was heard through the repeater's on board speaker, meaning it was coming through the antenna / recvr and not something produced in the rack I would assume. There is a cel tower about 1,000ft away and another tower with ( who knows ) how many other users, another 500ft further away. Based on this little bit of info what would the masses suggest in first FINDING the offending source if is indeed intermod?Then, is there much than can be done short of moving my machine? Any ideas or suggestions? * Mike
RE: [Repeater-Builder] OT Power Factor
This is funny. All they appear to be doing is placing a capacitor across the line at the service panel which gives some power factor correction to motor or other inductive loads. But that correction is AT THE POWER PANEL which is only inches or a few feet at the most away from the meter. If you are not being billed for reactive power but only for real power consumed, as you are in a typical home, then it does absolutely nothing for you. It does not lower the current in your motor and does not help prolong its life. It only lowers the current going thru the meter. And since that extra current is reactive it cost you no more or no less whether it is there or not. The other thing is, if you have no motors in inductive appliances running that capacitor is still across the line drawing CAPACTIVE reactance current. Just the opposite of when the inductive load is on by itself. You would need a capacitor reactance value to match the inductive reactance value to fully cancel any reactive current. Not that this hurts anything on you electric bill as you still get billed only for real power used and not reactive power. You have just given away $299.95. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Mike Reed Sent: Wednesday, February 11, 2009 1:42 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] OT Power Factor The device works by changing the voltage waveform to get the most work for the least energy. NASA came up with idea many years ago, and it does work well. I think this was designed more for household appliances and such, not repeater systems, unless you are counting the cooler that holds the 807's... 73 Mike - N7ZEF - Original Message - From: Don Kupferschmidt d...@httpd.org To: Repeater-Builder@yahoogroups.com Sent: Tuesday, February 10, 2009 1:44 PM Subject: Re: [Repeater-Builder] OT Power Factor Hello group, I need to chime in here and ask about a device that being sold as an enhancement for saving electrical energy in a residence. The device is called Power-Save 1200 and you can see it at www.power-save.com. From what I can glean from the web site it's a power factor correction device that attaches to the load center wiring panel.via 3 wires; 2 are attached to a dedicated 20 amp 2 pole 220 volt circuit breaker, the other remaining wire is attached to ground. The instructions go on to say that this device is designed to condition all power consumed by inductive loads (electric motors) in the home regardless of installation location. Their web site states: SAVE UP TO 25% ON YOUR MONTHLY ELECTRIC BILLS! (Direct quote). There is a video on the web site that shows a volt / amp meter reading before and after the device is activated. The unit sells for $299.95 + shipping handling. The dealer who told me about this device states that the unit will pay for itself over time. My brother in law is an electrician and we have gotten into a lively discussion about this device and the theory behind it. I say that while the device will probably work as advertised, it may not provide a complete savings to the owner as it is attached to the load center and not the individual motor. In essence, isn't the power company getting some benefit of this device since it's attached to the grid via the breakers which are being fed by the power company? TIA for your comments. Don Kupferschmidt, KD9PT - Original Message - From: Eric Lemmon wb6...@verizon.net To: Repeater-Builder@yahoogroups.com Sent: Monday, February 09, 2009 8:09 PM Subject: RE: [Repeater-Builder] OT Power Factor Tom, Excellent questions! The first is easy: Residences and light commercial occupancies have meters that measure real (true) power only. That's because only real power does work, and that's what you are paying for. The classic kWh meter with the spinning aluminum disk was perfected by Ferraris and Shallenberger more than a century ago, and millions are in service today. The most recent improvement is a magnetically-levitated disk that nearly eliminates any errors due to bearing friction. A revenue-grade kWh meter is extremely accurate, and very seldom requires service. True power is consumed only when the applied voltage and the resulting current are in phase. In this specific case, volts times amps equals watts. When the current is not in phase with the applied voltage, we enter the mysterious world of apparent power, which is expressed as volt-amperes. Nearly all apparent power seems to be consumed by inductive apparatus such as motors and transformers, except that such currents are returned to the source as the magnetic field collapses. Suffice it to say that the current actually flows in the circuit, but it does no real work. When the power factor (PF) is poor, a lot
RE: [Repeater-Builder] OT Power Factor
Kevin, I think that you meant the amperage to the load (a motor) is UNCHANGED with and without the device. I didn't notice the kwh reading on the meter. Good catch! 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Kevin Custer Sent: Wednesday, February 11, 2009 7:54 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] OT Power Factor I took the time to view their short video. http://www.power-save.com/1200.html They show the Amperage to the load (a motor) is changed with and without the Power Saver. Notice I said Amperage not KiloWatt Hours. KWH's are not referenced in the video, and is what you actually pay for for most residences. I wasn't sure exactly what the meter they were using was reading, so I downloaded the manual and read through it to see what was being displayed: http://www.tequipment.net/pdf/LEM/2050_man.pdf Page 14 tells the story here... If you look closely, the hand-held meter is simultaneously reading kW (the upper most reading). In the first demonstration, the kWh reading does not change with the unit on or off. In the latter two demonstrations, the kW reading GOES UP. I'm uncertain why the kWh reading (the reading closest to the bottom) doesn't show the change, maybe the meter takes a while to recalculate Smoke - Mirrors... So, you pay $300 (plus installation) to benefit the power company; which you get nothing in return, other than it possibly costing YOU more money on your electric bill. Kevin Custer List Owner Yahoo! Groups Links
RE: [Repeater-Builder] OT Power Factor
No you wouldn't have seen any change in the kwh reading in an hour because there is no change in real power which is what kwh is. If you were measuring kva (volt amperes) then that would change. I would assume that the kwh reading on the (handheld) meter would be instantaneous. Otherwise you would have to wait an hour in order for it to give you a reading of any kind. No different than reading horse power on a meter on a dyno. Or for that mater even rpm on an rpm meter. You don't have to wait a full minute or read revs per minute. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Wednesday, February 11, 2009 8:36 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] OT Power Factor The kWh reading didn't change because the time was too short. If they ran the test for an hour on, reset the meter, then an hour off you could have more easily seen a result -- it wouldn't have mattered -- no savings. Chuck WB2EDV - Original Message - If you look closely, the hand-held meter is simultaneously reading kW (the upper most reading). In the first demonstration, the kWh reading does not change with the unit on or off. In the latter two demonstrations, the kW reading GOES UP. I'm uncertain why the kWh reading (the reading closest to the bottom) doesn't show the change, maybe the meter takes a while to recalculate Smoke - Mirrors... Yahoo! Groups Links
RE: [Repeater-Builder] OT Power Factor
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Kevin Custer Sent: Wednesday, February 11, 2009 8:33 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] OT Power Factor Gary Schafer wrote: Kevin, I think that you meant the amperage to the load (a motor) is UNCHANGED with and without the device. I wasn't very clear What I meant was the amperage to the load from the first ammeter is changed by the presence the unit. Of course, the amperage to the load from the second ammeter is unchanged with or without the device; which goes on to prove the unit really doesn't do anything... It sure doesn't save on the motor! Kevin Exactly Kevin! And to further this,, I am assuming that the first ammeter is on the line between the meter and the device and the second ammeter is on the line between the device and the motor. 73 Gary K4FMX
RE: [Repeater-Builder] OT Power Factor
Sorry Chuck, yes I did misunderstand your comment. I got ahead of myself on kw verses kwh. You are right. Thanks! Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Wednesday, February 11, 2009 9:03 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] OT Power Factor You misunderstood my comment. I agree, there would have been no difference in the readings whether the device was on or off. However the kWh reading would have changed had it been left on long enough, and there was load. Kevin said that the kWh reading didn't change and didn't understand why. Chuck WB2EDV - Original Message - From: Gary Schafer gascha...@comcast.net To: Repeater-Builder@yahoogroups.com Sent: Wednesday, February 11, 2009 8:51 PM Subject: RE: [Repeater-Builder] OT Power Factor No you wouldn't have seen any change in the kwh reading in an hour because there is no change in real power which is what kwh is. If you were measuring kva (volt amperes) then that would change. Yahoo! Groups Links
RE: [Repeater-Builder] OT Power Factor
Your typical home meter measures only real power consumed. There is no such thing as reactive power being delivered to you. Any reactive power that you may be concerned with will originate on your side of the meter at the load. You really don't care about it there either as long as the extra current does not cause excess resistive loss in your wires going to the meter. You could hang a large capacitor across one of your outlets and draw say 20 amps of current and the power meter would barely move. The only power that would be consumed would be from any resistive drop in the wire between your capacitor and the meter and any losses in the capacitor. The power company usually cares about large amounts of reactive power as it shows up to them as additional line loss. 73 Gary K4 FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of albemar...@aol.com Sent: Monday, February 09, 2009 11:39 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] OT Power Factor Very interesting subject. People don't seem to be concerned about what kind of energy they are receiving from electric power company suppliers. I've asked previously for information about what people get in their homes and repeater sites with only one response telling me taps are available to solve a high or low problem. Do phase shift capacitors have an effect on our home our test equipment, repeaters? The AC specs here are 115.2 - 124.8. A calibrated NBS Fluke 77 reads consistently on the high end, and frequently up as high as 128. The power company engineer says they can do nothing about it, that taps do not exist anywhere in the system to lower the line voltage. Only phase shift capacitors. Our older test equipment designed around a 115 volt line plus AC motors, power transformers can have a problem with saturation. On a room to room/ garage/ shop investigation how many transformers, motors are in your dweling? Those big honker 30 amp or higher power supplies on repeaters going up in smoke. What's in your walletI mean your electric service line? GaryK2UQ In a message dated 2/9/2009 7:30:24 A.M. Eastern Standard Time, wb2...@roadrunner.com writes: Depends. Some customers are metered for reactive demand. It would matter then. Chuck WB2EDV - Original Message - From: Thomas Oliver mailto:tsoli...@tir.com To: repeater-builder@ mailto:repeater-builder@yahoogroups.com yahoogroups.com Sent: Monday, February 09, 2009 2:43 AM Subject: [Repeater-Builder] OT Power Factor Question for any electrical engineers out there. Are the meters on the side of buildings metering real power or apparent power? Is power factor correction worth doing if the power company is not dinging the customer for low power factor? This article http://powerelectro http://powerelectronics.com/power_management/motor_power_management/705PET2 3.pdf nics.com/power_management/motor_power_management/705PET23.pdf talks about residential power factor correction and my conclusion (from this article) is the savings would never be recouped. Second conclusion is the only benefit with correction is the wires between the source and load don't heat up as much. What about the wires in the motor or transformer? do they also heat less? I would think so. Third conclusion is by correcting power factor you are helping the utility company more than yourself because these phase differences standing waves exist all the way back to the power generation source therefore the utility lines have more loss due to their greater length than the customers building wiring has. The reason I am researching this is a customer of mine has roughly 50 hp of total motors in his shop and wanted to know if he could save 30% on his electric bill like some salesman of power factor correction black boxes told him he could. I realize I am going to have to look at his energy bill to see if there is a charge for low power factor and maybe call the utility company to see if he will get a lower rate if he adds PFC devices tom (\__/) ... (='.'=) ()_() _ Who's never won? Biggest http://music.aol.com/grammys/pictures/never-won-a-grammy?ncid=emlcntusmusi0 003 Grammy Award surprises of all time on AOL Music.
RE: [Repeater-Builder] Re: Hamtronics Helical Resonator Preamp or Advanced Research Preamp
The preamp had better amplify all things equally! If it doesn't then it is non linear and you have an intermod generator connected to your receiver. But if the preamp is driven hard enough by a strong signal(s) to drive it into compression then it becomes non linear. A condition that you want to avoid. Amplifying noise along with signal is a common result of any amplifier. If the noise is already there at the site the preamp is not going to increase the signal to noise ration no matter how much or little gain it has. Once you have site noise that is higher than the noise figure of your receiver or preamp then any more or less gain or better noise figure front end will do nothing for you as to signal to noise ratio. In other words it won't help you hear any better. Adding a preamp to a receiver reduces the intermod rejection capability of a receiver by the amount of gain added by the preamp. A 10 db gain preamp reduces original IM spec of the receiver by 10 db. This is the main reason you want to add only enough preamp gain as necessary. There are two ways to increase intermod performance in a receiver. One is to reduce the bandwidth of the receiver front end to limit or reduce the total amount of energy reaching the receiver. This was commonly done by using the helical and other type of front end filters in older radios. The other way to increase intermod performance is to have higher dynamic range front ends in the receivers. This is the case with more of the modern receivers and is why you don't see as many with the multiple front end filters that the earlier radios had. The front ends are capable of handling more energy (greater number of signals entering) without overloading. The sharper the filter ahead of the receiver or preamp the less total energy enters the receiver. Here I am talking about off channel energy, the stuff you don't want. All signals that reach the receiver add together and reduce the total energy handling capability of the receiver. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Barry Sent: Thursday, February 05, 2009 11:52 PM To: repeater-builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Hamtronics Helical Resonator Preamp or Advanced Research Preamp What he is saying is , a lower gain preamp aplifies less noise in relation to the signal so the audio sounds better _ To: Repeater-Builder@yahoogroups.com From: lar...@hotmail.com Date: Fri, 6 Feb 2009 04:47:11 + Subject: [Repeater-Builder] Re: Hamtronics Helical Resonator Preamp or Advanced Research Preamp --- In Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com yahoogroups.com, Joe Burkleo joeburk...@... wrote: If for example the site has a higher than normal noise floor a lower gain preamp will often times amplify more of the signal and less of the extra site noise, where a higher gain preamp may amplify both the noise and signal, giving you a signal with more noise than you would like. Joe, scratchin' my head here... Would you be able to clarify the above statement for me? Laryn K8TVZ _ Get what you want at ebay. Get rid of those unwanted christmas presents! http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Frover%2Eebay%2Ecom%2Frover% 2F1%2F705%2D10129%2D5668%2D323%2F4%3Fid%3D10_t=763807330_r=hotmailTAGLINES _m=EXT
RE: [Repeater-Builder] Site Insurance Vendors
Hi Nate, Can't members of the club be held liable as well as officers? 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Nate Duehr Sent: Monday, January 26, 2009 8:31 PM To: Repeater Builder List Cc: repeater-builder@yahoogroups.com Subject: Re: [Repeater-Builder] Site Insurance Vendors Yeah I know. I just didn't want to depress people further. If you have considerable assets, of any kind -- being a club leader is inherently a very risky position to put yourself in, financially -- now that corporate rules regarding liability of organizations have been eviscerated. Thank Enron and Qwest leadership for the motivation to change the law the next time you see them. ARRL says little about this. They have a whole organization dedicated to clubs that never says a word in any publication about how to properly set up Amateur organizations from a liability standpoint. At least my AOPA membership means they lobby for product liability changes in aviation. If ARRL ever starts fighting for liability limits for volunteer organizations in The Beltway instead of the never-ending BPL fight, I'll be pretty impressed. -- Nate Duehr Sent from my iPhone On Jan 26, 2009, at 17:49, Butch Kanvick hot...@hotmail.com wrote: Usually when some one signs a waiver letter, it is not worth the ink that it is written with. You cannot assign your rights away before something happens, it usually means you have just admitted liability with them signing the letter. It might slow down litigation by about 5 minutes, but does not mean anything. It is feel good measure, but good luck when it is used against you. Butch, KE7FEL/r _ To: mailto:Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com From: mailto:n...@natetech.com n...@natetech.com Date: Mon, 26 Jan 2009 17:12:39 -0700 Subject: RE: [Repeater-Builder] Site Insurance Vendors Check to see if they can later subrogate in cases of negligence or gross negligence in your state. In California, I think it's gross negligence, but I'd have to check. Sure they have to defend you, but if they lose... then they can usually turn around and sue you. And... this becomes a conflict of interest, because in States where they can subrogate only in cases of GROSS negligence (you have to get the difference between negligence and gross negligence here...), they're motivated to provide you with a really shoddy defense. Basically the old adage comes true again -- any lawyer you're not paying out of your pocket, isn't looking out for your best interests, they're looking to the best interests of their CLIENT. In this case, the insurance company. Let's use a real-world example: Someone falls off a tower and is hurt. It'd be REALLY easy for any lawyer involved to prove GROSS negligence today if everyone climbing didn' t have FORMAL OSHA-Approved climbing training. Send one guy up the tower who VOLUNTEERS to do so without modern training, and he falls, and you don't have a signed waiver from him -- if you're an officer of the organization, be prepared to lose your house to his widow. This is the kind of stuff that keeps club Presidents and officers awake at night when it's time to replace antennas. Nate -Original Message- From: Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com yahoogroups.com [mailto:Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com yahoogroups.com] On Behalf Of Dave Gomberg Sent: Monday, January 26, 2009 3:06 PM To: Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com yahoogroups.com Subject: RE: [Repeater-Builder] Site Insurance Vendors At 13:34 1/26/2009, Nate Duehr wrote: Also consider that most of your Bo ard and Officers will be bankrupt from paying for the lawyers to defend themselves (let alone the organization) long before the insurance kicks in... Nate You picked a bad state, Nate. In California, an insurance company has a duty to defend, even if they think the suit is baseless or not covered by your policy (they must defend to ensure that they get that ruling). And they pay for the defense. FWIW, I am not a lawyer nor do I play one on TV, this is NOT legal advice. -- Dave Gomberg, San Francisco NE5EE gomberg1 at wcf dot com All addresses, phones, etc. at http://www.wcf.com/ham/info.html http://www.wcf.com/ham/info.html -- Yahoo! Groups Links
RE: [Repeater-Builder] Coax Interconnect (Inside Repeater)
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Mike Pugh Sent: Wednesday, January 21, 2009 4:39 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Coax Interconnect (Inside Repeater) John J. Riddell wrote: Mike, the BNC connector was designed for quick insertion / disconnect and works very well in most applications. I keep forgetting why I don't post here very often. You're absolutely correct John. I never said that they were permanent substitutes for each other, I said they would work as a temporary substitute for each other in the event you were at a tower site and did not have the correct connector. If you have a choice of using the wrong connector and getting the station back on the air, or leaving it off and driving back to town to get the right connector, then they will mate for each other till you can get the right connector... Mike One caveat: While a type N male will plug into a BNC female, the N center pin is a little larger than that of a BNC. Doing this will expand the sleeves in the female BNC and when you go to put a BNC male back in (with the smaller pin) it may not make good contact again. Sometimes you can get away with it and sometimes you permanently damage the BNC female. 73 Gary K4FMX
RE: [Repeater-Builder] Re: Helper Instruments
Hi Skipp, What's a Helper RF millivoltmeter manual worth to you? I have one that I will scan for you when I get back home in a couple of weeks. No charge. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of skipp025 Sent: Thursday, December 25, 2008 1:27 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Helper Instruments Hi Dan, Glad to see you chimed in on this thread. Dan Graybeal dangerousengineer...@... wrote: The SM-512 is a service monitor that covers 1 to 512 MHz if memory serves correctly. I had incorrectly posted the follow up model as the SM-1024, but it was actually the SM-1000 as later indicated. (I was thinking in hex again...) It has a built in Sinadder and Millivolt meter. The system was designed around a Bearcat scanner. When Bearcat quit making the scanner, the system was redesigned from scratch and expanded to go to 1GHz, hence the SM-1000. If you look at the boards inside the SM-512 you will be able to identify the Bearcat model from the processor board. And more than one of us learned to use a Bearcat Scanner as a fairly strong signal source. Really neat Helper Instrument trivia... More than a few of the (now retired) local/regional Comm Shop Owners have told me stories of how a Helper Sales Rep would often loan Sinadder and similar demo products out to a shop to quickly prove their real on the service bench dollar value. Not only were the Helper Products well thought out, but those early sales folks including Bill were quite innovative. We made a bunch of neat stuff at Helper while Bill Detwiller (the owner) was still alive. I have a transitional Helper Catalog where shortly after Bill's passing his daughter announced a plan to go forward and continue operations. Not much is known to us the general public about the wind down of production and operation of Helper. As a Zetron Products Dealer one of the inside technical products support people told me about their purchase of some Helper Products, which were later discontinued as the Land Mobile Industry started to fall out of bed. I will look to see if I still have a users manual for either of these still around. I have a modest number of Helper Instrument Manuals but nothing for the Service Monitors or the RF Millivolt Meter, which I would pay dearly for (a copy of the RF mV Meter manual). Of course anyone nice enough to share would know I (or others) would pdf scan the manuals and donate copies to the Repeater-Builder and other similar web sites. The Helper 800 cell antenna performance instrument works fairly well for low 900 Amateur Band work. Not to mention the even more rare 460 band version. cheers, skipp skipp025 at yahoo.com Yahoo! Groups Links
RE: [Repeater-Builder] Re: Helper Instruments SM-512 and SM-1024
Helper never printed a service manual for the SM512. Only a operators manual was ever issued. It does have a schematic and some adjustment information in it. I have a copy of the manual. I thought I had it with me at my temp qth but I don't see it. If you will email me after the 1st of the year I should be able to find it and will send it along. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of skipp025 Sent: Tuesday, December 23, 2008 8:19 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Helper Instruments SM-512 and SM-1024 Hi Randy, You'll be hard pressed to find the Service Manual unless one of the manual sharks (people selling manuals) has one. The only other source I've seen for the manual has been one or two of the SM-512 units I've seen up on Ebay in the last two years. A fairly well thought out basic service monitor. Like most every Helper Product ahead of it's time and made with saving the comm tech time and money. Later version was the SM-1024. Helper Instruments was in Florida, growing out of a line of well thought out instruments targeted toward the Two-way radio industry. The owner of Helper passed and his daughter tried to keep things going but was unable to continue with new innovative products that separated Helper from the competition. Sometime later she sold interest in some specific Helper Products to Zetron. After a short time even Zetron discontinued production of their Helper Instruments products. The SM-512 Service monitor (and the later SM-1024) were very special animals (products) not produced or continued by Zetron. The one NY located service center (person) for the SM-512 passed some years back and the legacy of Helper slowly fades into history. I have a fair number of Helper Instrument Products and manuals... but sorry nothing for the SM-512 and SM-1024. cheers, skipp skipp025 at yahoo.com wb8art wb8...@... wrote: Anyone have a operations manual and or service manual for a Helper Instruments SM-512 Randy Yahoo! Groups Links
RE: [Repeater-Builder] Re: Please help with split site
The main reason higher gain antennas on a link are desirable is to narrow the beam width so that you don't pick up as much or transmit as much interference to/from undesired stations. Horizontal polarization as mentioned also helps reduce the interference problems. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Thursday, November 06, 2008 3:45 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Please help with split site Mmmm. I was told (on this group) that my 8-elements was too much. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Stephen Reynolds Sent: Thursday, November 06, 2008 3:04 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Please help with split site Add to all of the other good info here, make your link antennas Horizantal polarization with atleast 10 elements on each. Steve W4CNG
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs.
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Hi Mike, I am a little confused as to how you are coupling the signal generator to the receiver. When you have the tx and rx connected to the duplexer normally and a dummy load on the output T (that would normally feed the antenna line) how are you coupling the signal generator to the receiver? Are you using an isolated T in the receive line to couple the generator in? 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 8:21 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Gary, At this juncture, I'm not getting scientific about the actual desense measurement, but I can tell you it's in the ten's of dBs. At this point, I'm using Kevin's method. signal generator connected to the cans with the cans connected to the repeater normally. I set the signal generator to the point that the squelch breaks and turn the transmitter on manually. If the signal stays there. I'm happy (at this point). If not. I increase signal generator level until I keep the signal with the transmitter on. As I said. it's ten's of dBs at this point You're correct about where I'm connecting the dummy load. Again. I'm not using ANY antennas at this point. All testing is done into the -8920 and/or the dummy load. I'm confused about your last statement. I've not put a load at the end of the tee that feeds the feedline. If I do that, I can't feed signal to the receiver. If I take the TX line off the tee and put a dummy load there, there is no desense. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 8:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs.
RE: [Repeater-Builder] LMR-400 Cable
Hi Tom, As others have said, try the dummy load at the antenna end of the cable and see if there is any desense. Then try disconnecting the antenna input to the receiver from the duplexer and place a dummy load on the receiver. Turn on the transmitter and see if you still have desense. If you do then your receiver is probably picking up RF from the antenna and causing the problem. Since you do not get the desense with a dummy load on the duplexer output this will verify/eliminate direct radiation from the antenna. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Tom Elmore Sent: Wednesday, October 01, 2008 12:06 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] LMR-400 Cable I recently put a six meter repeater (52.810/51.110) on the air here in Anchorage, Alaska. I am feeding it with about 60 feet of LMR-400 cable and am experiencing quite a bit of desense. I did a search for LMR-400 in duplex operation and came across several posts from users of this list and decided to sign up and investigate some more. I am running a GE Master Pro at 100 watts into a 8 cavity Sinclair duplexer. The antenna is a Diamond co-linear mounted about 35 feet above ground at the present time. I live on a hill here in town and currently have the repeater mounted at my home qth. When I terminate the duplexer into a dummy load and look at it with the spectrum analyzer it performs very well with no desense. Connecting up the antenna is another story altogether. I have been pulling my hair out over this one thinking it must be a duplexer problem. Originally I fed the antenna with RG-213 which I know is not the best choice for repeater use but it is what I had handy at the time. I was getting desense with the RG-213 so I switched to the LMR-400 since I had a roll someone had given me. I actually think I had slightly less desense with the RG-213. Is the 400 really not that suitable for duplex operation even at 6 meters? What would be a good alternate choice ? Thank You Tom Elmore KA1NVZ Anchorage, Alaska
RE: [Repeater-Builder] Re: Does anyone else think of Power Factor like SWR?
Yes standing waves can exist with a pure resistive load on a line but the mismatch of the load with the line impedance creates a reactance (depending on line length). A transmission line must be long enough (wavelength wise) for standing waves to exist. A short line (wavelength wise) like an audio cable, will not exhibit standing waves because it is too short for them to exist. Even a short (wavelength wise) RF cable will not exhibit standing waves. Keep in mind that the typical SWR and power meters that we use to measure SWR with are NOT really measuring SWR. They are measuring impedance mismatch of the internal impedance that the meter is set for, with a scale on the meter that converts the impedance ratio to a would be SWR. A very long power transmission line can have standing waves on it if the power factor problems are not kept in check. So power factor could be thought of like SWR but only on long distribution lines. Keep in mind that short transmission lines whether it be power, audio or RF do not have standing waves on them when they are very short wavelength wise. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Nigel Johnson Sent: Saturday, September 20, 2008 7:26 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Does anyone else think of Power Factor like SWR? Very interesting theory. I am teaching SWR at present to my third year college students. Could be a good discussion point since they have already studied power factor. However, SWR can exist with a purely resistive mismatched load, so it needs a bit of modification to take all into account. 73 Nigel ve3id --- In Repeater-Builder@yahoogroups.com, Bob Witte K0NR [EMAIL PROTECTED] wrote: --- In Repeater-Builder@yahoogroups.com, kb9bpf kb9bpf@ wrote: Since I'm way more into RF than industrial power distribution, I've always been able to think of power factor on the electrical power grid in terms similar to antenna system reflections, which are commonly measured in terms of SWR. After all, both are AC systems where the voltage and current bear a phase relationship to each other. When they are perfectly in phase the power factor is 1.0, and a 60-Hz SWR meter would measure 1:1. When they are out of phase (power factor 1) that SWR meter would read greater than 1:1. I suspect, though I haven't done the math or looked up the specific matahematical definition of power factor, that it would be direcly proportional to the reciprocal of the power factor. And as we know, when that happens the power generating end has more difficulty delivering power efficiently to the load. A while back I was doing some analysis of power factor to understand it better and I found that it has a lot in common with SWR. Both are focused on the issue of power transfer, so I guess we shouldn't be surprised. The thing they really have in common is for max power with AC signals, the voltage and current need to be in phase (phase angle of zero). For linear systems with nice sine waves, PF = cos (phase angle) where phase angle = the angle between voltage and current sinusoids Wikipedia has a good explanation of PF at http://en.wikipedia.org/wiki/Power_factor Play around with some typical circuits and you'll find that an SWR of 1 also has voltage and current in phase. Again, not a surprise since it represents the best power transfer. This is from memory, so the usual disclaimers apply :-) 73, Bob K0NR Yahoo! Groups Links
RE: [Repeater-Builder] Re: Cable Q-- Please Define
I think cables and cavities are being mixed up a littler here. When using hard line cable to build the cavities for a 6 meter duplexer then that hard line is not operating as a typical coax line. It is operating as a quarter wave resonant cavity. It has a high impedance on one end and a short on the other end. Very different from the way a typical coax cable is operated. Yes Q does matter in a cavity. The only reason to increase insertion loss in a cavity is when more selectivity or a deeper or narrower notch is needed. Most often cables within combiners / duplexers work in harmony with the associated cavity. Replacing one of those cables with a poorer quality cable will only reduce (if any difference is noted) the amount of rejection that was obtained from that cable and cavity combination. Those cables are usually operated as quarter wave shorts in these circuits at some specific frequency. At other frequencies they operate as regular non resonant coax cable in the circuit. Duplexers, combiners, coax cables are all passive devices. By their nature they do not produce intermod or any other signals, unless of course if they are defective. Some transmitters (and some receivers) do not like reactive loads off frequency. Even though a duplexer or transmitter combiner may present a flat or nearly flat load at the wanted frequency, that same duplexer may present enough of a reactance off frequency to cause unwanted oscillations in the transmitter. In a case like that changing ANYTHING in the circuit can have an effect on the transmitter's ability to remain stable. That is why sometimes changing cable lengths between the transmitter and duplexer can cure some problems. (normally this cable length is non critical) (changing this cable length can also have an effect on power output of the transmitter at the wanted frequency because of the load that it sees on the wanted frequency) Yes that interconnect cable can have Q associated with it if it is transforming an impedance from one value to another at some unwanted frequency. But when the cable is operating as a regular coax cable transferring power at its nominal impedance Q is not a factor to be considered. In the case of parasitic suppressors in an amplifier circuit Q is reduced by the suppressor at some specific unwanted frequency. The circuit Q of the wanted frequency is not changed. This reduces oscillation tendency at the unwanted frequency by reducing the gain of the amplifier circuit at that frequency. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of skipp025 Sent: Friday, September 05, 2008 1:47 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Cable Q-- Please Define Higher Q parts/paths MAY sometimes support unwanted/parasitic action/energies otherwise not normally sustainable when losses in lower Q circuits overcome those paths/sources. An example... The six meter duplexer made from 1-1/4 and 1-5/8 inch hard line can also be made of common coax. The Q of the common coax is relatively low enough so the flexible coax version won't work very well, the higher Q 1-5/8 inch line being the better choice. Both the 1-1/4 and 1-5/8 inch home-brew rigid line duplexers are considered usable... graphs of both rigid line version are on the various web pages and clearly show the performance numbers. If you experience a grunge/imd problem with/through using the better 1-5/8 inch hard line duplexer... the same mix/grunge/intermod problem might not be sustained(able) through the 1-1/4 duplexer because of it's higher internal loss (lower Q). Keep in mind the 1-1/4 inch diameter hard line 6 meter duplexer is still quite usable. In common land mobile antenna combiners... we can and do increase the cavity, coax and network insertion loss to reduce problems in some specialized cases. A lot of this is just about trying to describe how sometimes a reduction in an antenna/duplexer hardware and feed-line Cable Q (quality) can attenuate unwanted energies. In my opinion the South American Telewave VHF Transmit Combiner story we saw here on the group a while back was very much about having high-Q cavities and very, very small amounts of unwanted energies fairly possibly solved with a number of modest changes including increasing the loss numbers on some of the combiner channels. The combiner was engineered by Telewave and the potential mix numbers looked pretty darn good. But the as-built hardware had mix problems no-one seemed to be able to source using the off the shelf tricks. Reducing the Q of a circuit was probably not an off the shelf method used or even thought about by most people. When working on/with high powered tube rf amplifiers we often use parasitic suppressors to reduce Q and make the amplifier ultra stable. Reducing the circuit Q a slight amount is enough to prevent unwanted parasitic
RE: [Repeater-Builder] Height Gain figure
My reply was strictly tongue in cheek as to the amount of range increase that would be obtained. As the other poster claimed that adding 100 feet to some unknown antenna height would yield an additional 14 miles range. Free space loss is not going to be a factor in a normal repeater system. Unless of course you are starting out with microwatts of power. After all you only loose 6 db every time you double the distance in free space. There are many other factors that will cause attenuation of the signal that will dominate free space loss. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Eric Lemmon Sent: Sunday, August 10, 2008 11:42 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Height Gain figure Probably not. The range of any repeater or base station is limited by the ability to receive a signal from the units in the field, not by the amount of power at the base or repeater station. At some point, the free-space losses will prevent the unit in the field from getting a usable signal into the base station- even if there is a line-of-sight path. This doesn't happen very often, due to the curvature of the earth, but it is a physical barrier that exists. We often assume that a line-of-sight path is a guarantee of solid communications, but it doesn't work that way. After all, you can't use a handie-talkie on the moon to talk through a repeater on Earth, even though you might have a clear line-of-sight path. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Sunday, August 10, 2008 9:20 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Height Gain figure So if the antenna is already at 1000 feet height and it is moved up another 100 feet to 1100 feet, you are going to increase the range by 14 miles?? 73 Gary K4FMX From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, August 10, 2008 3:20 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Height Gain figure It is interesting to see the many responses, none of which I have problems with, but all seem to skirt your question. If you are moving the site any distance from the present site, then it is very true that these variables must be considered. If you are moving only a very short distance from your current site, then, I believe what you are looking for is a simple formula to givr a close guess of what to expect. I think you will find that should yout take the square root of the change in height, in this case, the square root of 100 which is 10, and mulitply that by the square root of 2, which is 1.414, you will come up with an approximattion of 14 or so miles improvement. Again, as others have pointed out, many variables inter into the equasion, but then, the bumble bee can not fly either. . . .. Hope this helps. 73 and cheers, Gene, W4FWG -- Original message from Chuck Kimball [EMAIL PROTECTED]: -- At one point I had read a number for figuring out the gain you get by increasing the height. Of course at the moment I'm unable to locate that. ie: If I move the same antenna (VHF 2m) up a hill and gain 100' of elevation, but it costs me the line loss (300'), did I really gain anything. I'll figure in the line loss, and adjust the hardline to minimize the loss, but I'm looking for the number to compare how much gain (in db) did I get with the increased height. So... Anyone know what number is for gain as a function of height? or know a reference I can look up. Thanks Chuck n0nhj Yahoo! Groups Links
RE: [Repeater-Builder] Height Gain figure
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Dave Gomberg Sent: Monday, August 11, 2008 8:37 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Height Gain figure At 16:42 8/10/2008, Dick wrote: An antenna's gain is what it is and it doesn't change with elevation. I am assuming you mean elevation over the surrounding terrain?? This is not true. For example, a dipole has an energy distribution pattern that changes markedly with height above ground. Just try using a NVIS for DX! And verticals become ineffective at very high installation points unless special steps are taken to compensate (by improving the counterpoise). Anyway, that's my opinion and I'm stickin' to it. Once the antenna is several wavelengths above ground (as it will be with any reasonable height at VHF and above) the pattern is going to be the same no matter how much higher it is raised. The ground will have insignificant effects on the radiation pattern. 73 Gary K4FMX
RE: [Repeater-Builder] Height Gain figure
So if the antenna is already at 1000 feet height and it is moved up another 100 feet to 1100 feet, you are going to increase the range by 14 miles?? 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, August 10, 2008 3:20 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Height Gain figure It is interesting to see the many responses, none of which I have problems with, but all seem to skirt your question. If you are moving the site any distance from the present site, then it is very true that these variables must be considered. If you are moving only a very short distance from your current site, then, I believe what you are looking for is a simple formula to givr a close guess of what to expect. I think you will find that should yout take the square root of the change in height, in this case, the square root of 100 which is 10, and mulitply that by the square root of 2, which is 1.414, you will come up with an approximattion of 14 or so miles improvement. Again, as others have pointed out, many variables inter into the equasion, but then, the bumble bee can not fly either. . . .. Hope this helps. 73 and cheers, Gene, W4FWG -- Original message from Chuck Kimball [EMAIL PROTECTED]: -- At one point I had read a number for figuring out the gain you get by increasing the height. Of course at the moment I'm unable to locate that. ie: If I move the same antenna (VHF 2m) up a hill and gain 100' of elevation, but it costs me the line loss (300'), did I really gain anything. I'll figure in the line loss, and adjust the hardline to minimize the loss, but I'm looking for the number to compare how much gain (in db) did I get with the increased height. So... Anyone know what number is for gain as a function of height? or know a reference I can look up. Thanks Chuck n0nhj
RE: [Repeater-Builder] Re: Frequency Change do I retune duplexer?
If you see several db difference with a 12.5 KHz frequency shift then your duplexer is also distorting your audio on the transmitted signal. It would induce unwanted phase shifts and also unwanted amplitude changes in the transmitted signal. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of skipp025 Sent: Monday, June 30, 2008 1:49 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Frequency Change do I retune duplexer? Hi Paul, I go the other way where multiple Duplexer High-Q Series Cavities have a deep sharp reject notch and a 12.5 KHz shift from F-center results in a quite noticeable performance change. cheers, s. Paul Plack [EMAIL PROTECTED] wrote: The answer also needs to account for the fact that the duplexer might already be imperfect in its tuning, especially if it's old or has been moved around. 12.5 kHz one way might be fine...12.5 kHz the other direction might be noticeable. 73, Paul, AE4KR Yahoo! Groups Links
RE: [Repeater-Builder] Re: Frequency Change do I retune duplexer?
That is true for band pass filters but in the case of a duplexer the filters are usually notch type (or pass/notch). So the more notch type cans there are the wider the notch will be at some given frequency. Think of it as an upside down band pass response. Note that the pass response of a band pass / reject type duplexer is very wide to start with. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jim Brown Sent: Friday, June 27, 2008 4:32 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Frequency Change do I retune duplexer? Doug, It has always been my experience that adding two or more cans in series always narrows the bandpass, not widen it. The first can will show a given dB down at x frequency away from the center tune. Adding the second can will decrease the level by the sum of the two at the same x frequency from the center tune. The more bandpass cans you use in series, the narrower the bandpass. 73 - Jim W5ZIT --- On Fri, 6/27/08, Doug Bade [EMAIL PROTECTED] wrote: From: Doug Bade [EMAIL PROTECTED] Subject: Re: [Repeater-Builder] Re: Frequency Change do I retune duplexer? To: Repeater-Builder@yahoogroups.com Date: Friday, June 27, 2008, 11:22 AM 4 cans winds up in mhz wide as apposed to khz wide... ( as in an rx preselector, the more cans the wider it is) Doug KD8B __
RE: [Repeater-Builder] Re: Folded Diploles or Vertical antenna/Power Readings
Hi Skipp, I can't really tell if you are agreeing or disagreeing. :) A good, properly tuned isolator will absorb all reflected power that is of any consequence. In other words I don't think that you would be able to see any reflected power on the wattmeter from the isolator. A wattmeter in line with the load on the circulator could be compared with the reflected power meter reading in the antenna line. Or return loss of the antenna port on the isolator measured. Given that there is no reflected power from the isolator there will be no re-reflected power going back up to the antenna therefore the amount of reflected power on the line will subtract from the power that is available to be radiated. Without an isolator in place most of the re-reflected power is available to be radiated. With a Bird inline wattmeter it will give true forward power by subtracting reflected power from indicated forward power. It will do this regardless of the impedance of the line it is installed in. When connected to a transmitter without an isolator, if there is 10 watts of reflected power and a true 100 watts of power coming out of the transmitter, the Bird meter will read 110 watts forward and 10 watts reflected. Subtracting the reflected from the indicated forward power gives a net of 100 watts power going to the antenna to be radiated. This is of course less feed line losses. Also the small amount of re-re-reflected power from the original reflected power (second trip for the reflected) which will probably be too small to measure. The same Bird meter connected to the same antenna line but with the transmitter having an isolator should read 100 watts forward and 10 watts reflected. Subtracting the reflected from the forward should give a net power of 90 watts going to the antenna to be radiated. This time the load on the isolator will be absorbing the reflected power rather than it going back up to the antenna. All wattmeters may not work the same as the Bird in regards to reflected power. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of skipp025 Sent: Thursday, June 05, 2008 12:32 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Folded Diploles or Vertical antenna/Power Readings This is not entirely true. A transmitter with an isolator on it will absorb all the reflected power that reaches it. Not true... a circulator or isolator will deal with much of the reflected power... but probably never all of it. Note that forward power can sometimes read higher than true if there is more reflected power. What you actually read or see on a meter depends on a number of issues... like the type of sample unit and where it is in the feedline. And to answer something that one person came up with a while back, decreasing the reflected power does not add it to the true radiated power. Yep, just depends on where it's actually going. A good match at the power amplifier outpu presented by inserting a circulator or isolator doesn't tell you the antenna is in good condition or the power is actually heading out the door (the antenna). cheers, s.
RE: [Repeater-Builder] Wacom Duplexer Desense Problem - Mystery
A couple of notes on this: Beware of the mfj to read impedance/swr. I have an mfj 259B and it is terrible on 2 meters. With a GOOD dummy load it shows a higher swr the higher you go in frequency with it. I think it will show around 1.5:1 and an impedance of around 42 ohms on the good dummy load. On lower (HF) it works fine. The problems that you found with the cable may not have been because it was not double shielded. Especially if things changed as you wiggled it around. It may have been poor connector installation. Most people that experience cable problems do not look at the connectors as being installed improperly or braid broken loose from extended use. I used to sell service monitors to two way shops and would bring the monitors in the shop to demonstrate them. I found that about 80% of the test cables that the shop had (and used on a regular basis) were bad! Usually intermittent from bad connector installation. It seems kind of unbelievable that guys that were using this equipment in day to day work would not be aware of the bad cables. Just think of how many goofy problems could be avoided with known good test equipment. After a short time I always made sure that I brought my own cables along for the demo. I used to pick up coax jumpers at hamfests for use around my shack. I can't remember the last time I got one with the connectors installed properly (always loose connectors) other than commercially made cables. Now I don't even bother to pick them up anymore. Check those connectors. If you can rotate them at all on the cable they are not installed properly and will give problems. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of blisswheeler Sent: Sunday, May 11, 2008 12:38 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Wacom Duplexer Desense Problem - Mystery I really appreciate all of the comments on my duplexer mystery. I made sure everything was tuned properly and took it back to my friends home location. We put it back on the air and experienced 2db of signal desense with an output of 15 watts. That still doesn't duplicate the results of the dummy load test, but that's a far cry from the 30db I was experiencing here at my home shop. Some of the things I did learn from the experience was that: 1. Though an antenna may only have a 1.5 SWR doesn't mean that the antenna is a 50 ohm match. Using my MFJ (Mighty Fine Junk which, by the way work pretty darned good, but not in a high RF environment) antenna analyzer, the antenna that gave me the most difficulty presented an 80 ohm load. The SWR was 1.5. A discone antenna worked the best and it presented a 55 ohm load with a 1.2 SWR. 2. Double shielded coax is a must in repeater operation. I experienced this first hand. I had one short jumper I thought was double shielded and was not which caused an intermittent such that one time it worked into a dummy load and the next it went flaky. Moving the coax with the repeater transmitter keyed revealed the culprit. Use hardline or double shielded coax. Hardline to the antenna is very important. 3. Bench testing duplexers into a dummy load may not duplicate the results experienced with the antenna. 4. In theory isn't necessarily the same as reality. I suppose if you know all the variables the problem can be calculated and identified, but there are a lot of unknown variables when working with RF. 5. The environment your repeater is in can cause you to loose your hair. Yes it is related to the rf generated, no not because of the health effects but because it makes you tear your hear out trying to identify a problem. 6. I learned about whiskers in GE Mastr II receivers... I experienced their effects and how to fix the problem, though maybe for only a year or two, but I learned to to disassemble and retune the receiver. 7. Your experienced Techie RF friends are a great help. I have three good friends that gave me a lot of ideas and helped me trouble shoot this problem. The folks here on Repeater-Builder gave me some good tips which pointed in the right direction as well, for that I thank you all. Respectfully, Bliss Yahoo! Groups Links
RE: [Repeater-Builder] Wacom Duplexer Desense Problem - Mystery
Yes it is the MFJ. I have many good loads that I have also checked with a return loss bridge and tracking setup. They are very flat. I have talked to several others that have experienced the same problem with the MFJ. One guy told me that he changed out the SO239 jack to a type N and it was much better. I don't know if there are things to adjust in the MFJ to balance it at VHF or not. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Paul Plack Sent: Sunday, May 11, 2008 5:08 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Wacom Duplexer Desense Problem - Mystery Are you sure it's the MFJ? I thought my MFJ 259 was behaving badly at some frequencies, and it turned out to be the dummy loads. One in particular was flat everywhere but 6 meters, and it took me years to notice because I don't deal with that band often. I also have noticed the problems in high RF environments, but that's not MFJ's fault. No SWR bridge works accurately measuring an antenna with a few milliwatts at a 100 kilowatt broadcast site. Paul, AE4KR - Original Message - From: Gary Schafer mailto:[EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Sunday, May 11, 2008 1:56 PM Subject: RE: [Repeater-Builder] Wacom Duplexer Desense Problem - Mystery A couple of notes on this: Beware of the mfj to read impedance/swr. I have an mfj 259B and it is terrible on 2 meters. With a GOOD dummy load it shows a higher swr the higher you go in frequency with it. I think it will show around 1.5:1 and an impedance of around 42 ohms on the good dummy load. On lower (HF) it works fine. The problems that you found with the cable may not have been because it was not double shielded. Especially if things changed as you wiggled it around. It may have been poor connector installation. Most people that experience cable problems do not look at the connectors as being installed improperly or braid broken loose from extended use. I used to sell service monitors to two way shops and would bring the monitors in the shop to demonstrate them. I found that about 80% of the test cables that the shop had (and used on a regular basis) were bad! Usually intermittent from bad connector installation. It seems kind of unbelievable that guys that were using this equipment in day to day work would not be aware of the bad cables. Just think of how many goofy problems could be avoided with known good test equipment. After a short time I always made sure that I brought my own cables along for the demo. I used to pick up coax jumpers at hamfests for use around my shack. I can't remember the last time I got one with the connectors installed properly (always loose connectors) other than commercially made cables. Now I don't even bother to pick them up anymore. Check those connectors. If you can rotate them at all on the cable they are not installed properly and will give problems. 73 Gary K4FMX -Original Message- From: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] mailto:Builder%40yahoogroups.com .com] On Behalf Of blisswheeler Sent: Sunday, May 11, 2008 12:38 AM To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Subject: [Repeater-Builder] Wacom Duplexer Desense Problem - Mystery I really appreciate all of the comments on my duplexer mystery. I made sure everything was tuned properly and took it back to my friends home location. We put it back on the air and experienced 2db of signal desense with an output of 15 watts. That still doesn't duplicate the results of the dummy load test, but that's a far cry from the 30db I was experiencing here at my home shop. Some of the things I did learn from the experience was that: 1. Though an antenna may only have a 1.5 SWR doesn't mean that the antenna is a 50 ohm match. Using my MFJ (Mighty Fine Junk which, by the way work pretty darned good, but not in a high RF environment) antenna analyzer, the antenna that gave me the most difficulty presented an 80 ohm load. The SWR was 1.5. A discone antenna worked the best and it presented a 55 ohm load with a 1.2 SWR. 2. Double shielded coax is a must in repeater operation. I experienced this first hand. I had one short jumper I thought was double shielded and was not which caused an intermittent such that one time it worked into a dummy load and the next it went flaky. Moving the coax with the repeater transmitter keyed revealed the culprit. Use hardline or double shielded coax. Hardline to the antenna is very important. 3. Bench testing duplexers into a dummy load may not duplicate the results experienced with the antenna. 4. In theory isn't necessarily the same as reality. I suppose if you know all the variables the problem can be calculated and identified, but there are a lot of unknown variables when working with RF
RE: Re: [Repeater-Builder] Re: antenna question - Dip It and Scotch Kote and Kry
Any tower over 150 feet tall can get a direct hit on the side. It will not necessarily hit the top of the tower. A side mounted antenna on a tall tower is not a guarantee that it won't be hit directly. If a wire is run outside of a side mounted antenna and connected to the tower above and below the antenna it will shield the antenna from a direct strike. In other words the wire will be hit rather than the antenna. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Paul Finch Sent: Thursday, May 08, 2008 11:26 PM To: Repeater-Builder@yahoogroups.com Subject: RE: Re: [Repeater-Builder] Re: antenna question - Dip It and Scotch Kote and Kry Ron, Remember that lightning not only hits the top of the tower but can come back off the tower and hit something else in it's way, I think I heard in around 150 foot increments. The only hit of lightning that did any damage at my tower was from a direct hit that did no damage to the antennas or feedline. It apparently hit the tower near the top and came back off somewhere lower down the tower and hit the power pole next to the tower. It took out a lightning arrestor in a paging base which in turn opened the circuit breaker the base was on as well as the main breaker. No other damage. Paul _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Thursday, May 08, 2008 7:03 AM To: Repeater-Builder@yahoogroups.com Subject: Re: Re: [Repeater-Builder] Re: antenna question - Dip It and Scotch Kote and Kry Joe, I agree the 224 probably handles lightning better than the fiberglass versions. I think the folded dipoles being on a mast and the mast takes most of the hit where with the fiberglass the antenna itself takes it. I would not like to mount a fiberglass antenna on top without a top bracket. I've seen good quality new fiberglass antennas have wind static type noise on new installs due to blowing in the wind. I am sure the swaying over time takes it toll. Of course I like bottom and top mounts on all long antennas, but if top mounted is the install then the DB224 would be preferred. Thanks for you input. 73, ron, n9ee/r From: MCH [EMAIL PROTECTED] mailto:mch%40nb.net Date: 2008/05/07 Wed PM 02:12:33 CDT To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna question - Dip It and Scotch Kote and Kry I haven't had as many problems with lightning and the fiberglass antennas as I have with wind causing fractures in the connections between the elements. In the case of the coasts, you have to deal with that AND salt, so I doubt there is any good solution. The above said, I do believe the 224 type antennas do handle lightning better - I didn't mean to imply that they don't. I'm only saying in those I've seen wind is the bigger threat. In the case of a top mounted antenna, there is no way to stabilize the top of the fiberglass antenna. Joe M. Ron Wright wrote: Dick, This discussion of weather proofing an antenna was started in part because I am replacing a 4 bay DB224 up high and near the Gulf of Mexico. We think the salt air got to it. We have had similar problems in the past. The antenna has been up for about 12 years. I was looking for a solution to the salt air. The painting issue came up because of this. I am replacing with a Telewave ANT150F6-2 fiberglass enclosed antenna. However, many have had problems with these and the Celwave or RFS Super Station Master with lightning. They do not handle the lightning as well as the DB224 due to, one reason, some use solder to hold the elements together inside the radome. However, mine is side mounted and hope this will not be a problem. The salt air is. I like the Station Master, but also like the DB224. On VHF one does not get easily 10 db gain out of a RFS Station Master, in fact more like 4.7 db for the 140-150 MHz antenna. The Telewave uses a longer fiberglass radome for its version allowing all the elements to be inserted. The UHF version does have higher gain, 9 db, gain. The folded dipoles allow squewing the pattern easier and more than the station master. About all it will allow is moving around and in/out from the tower. The folded dipoles are much more flexible in this issue. Lots of good responses on this. Know many learned a lot. I did. 73, ron, n9ee/r Er.. uh... Excuse me, but why all this commotion about painting and preserving antennas??? If everyone used limited range, low gain, stacked folded dipoles, then maybe so, but stacked folded dipoles are a low gain limited range item. I've seen them used in small towns with limited coverage Public Safety fleets, and Local Paging, but only where limited range coverage is required. When I worked in Mobile Radio Communications ALL Remote Base / Repeater antennas were stacked coaxial antennas inside a
RE: [Repeater-Builder] Wacom 642
If it were me asking that question, I would be saying thank you to Eric. Not everyone knows that some of the commercial manufacturers are very supportive of ham activities and that they have that sort of information readily available. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Dail Terry Sent: Friday, April 11, 2008 8:28 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Wacom 642 Eric, You may have lost track of the fact that this is a site to ask questions and people knowledgeable in the subject answer. (Note the answer Bruce gave to the question) The answer you gave makes me wonder if it isn't time for you to step back and re-evaluate your position on this board. There are some very talented people very willing to share their experience and knowledge. With an answer as you gave, it appears as though you are NOT one of them. Next time I ask a question, please don't bother to answer. Dail N6DGT - Original Message From: Eric Lemmon [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, April 10, 2008 7:09:53 PM Subject: RE: [Repeater-Builder] Wacom 642 Dail, If TX-RX is no help (you DID contact them first for assistance, didn't you?), then contact Telewave at www.telewave. com. Telewave makes it their business to keep former WACOM customers happy. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups. com [mailto:Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups. com] On Behalf Of Dail Terry Sent: Thursday, April 10, 2008 8:25 AM To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups. com Subject: [Repeater-Builder] Wacom 642 We are working with a set of Wacom WP642 duplexer cans that is missing the T UHF connector and the coax that goes to the first cans. Does anyone have the dimension for the coax? The rest of the cabling is made up with RG 213U. As Wacom is no longer in business (taken over by RX TX) I cannot find the info. TX Dail N6DGT __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
RE: [Repeater-Builder] Static on grounded feed line system.
You need a HI-pot tester to check the protection devices. You crank up the voltage until they show a breakdown and see if it is breaking down at the proper voltage for the device. It will not harm them at all as the current is only a few micro amps.. Polyphaser used to market a small test set they called the FIST. They may still have it?? It was a small automatic hi-pot tester with a meter that read out in Kv. The voltage would rise to the breakdown point and stop. You read the meter for the breakdown voltage. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Radioman Sent: Friday, April 04, 2008 8:49 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Static on grounded feed line system. I replace the Polyphasers at the sites I'm responsible for every two years, or sooner if a direct strike is suspected. Just because they pass RF OK doesn't mean they're still doing the job efficiently. I believe it is cheap insurance even it means replacing a half dozen or more at one site. I have recently heard that there is a new series on the market which may not require replacing except after a direct strike. I need to do more research on those. Maybe someone here has info on those? Harry, W0OZL - Original Message - From: Paul Plack mailto:[EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Friday, April 04, 2008 1:45 AM Subject: RE: [Repeater-Builder] Static on grounded feed line system. Sorry for being a few days behind on e-mail, but...don't those gas tubes need replacing eventually? Maybe after 8 years, they've given all once too many times to stay on the job.
[Repeater-Builder] Cascade noise figure calculator
Here is a cascade noise figure calculator. Play around with different gain figures and noise figures for the first amp to see how it affects the total noise figure. Consider the second amp your receiver. Put in an 8 db or so figure for the second amp to simulate your receiver. You will see that as you increase the first amp gain the overall noise figure does drop some but not by as much as the gain increase. You can simulate a pad between the preamp and your receiver by increasing the noise figure of the second amp by the amount of pad you would use. It is not quit the same as reducing the gain of the preamp (first amp) but close. http://www.minicircuits.com/pages/mcl_nf_calc.html 73 Gary K4FMX
[Repeater-Builder] Tracking generators and sweep generators
For clarification: A SWEEP GENERATOR is just a sweep generator by itself and is generally used with a diode detector and a scope to view the output signal of whatever is being swept. The sensitivity (dynamic range) is limited by the sensitivity of the diode which is usually in the neighborhood of -40 dbm. So if your sweep generator puts out zero dbm then you can see down to -40 dbm in level. Good for tuning pass band cavities or IF filters etc. but not enough sensitivity to tune a notch filter where you need to see down at least -70 to -80 db or more. You can add an amplifier before the diode detector or to the output of the sweep generator to gain a little more range but if you go much over 20 db in gain you start running into overload problems with the auxiliary amp. A TRACKING GENERATOR uses the same type of sweep generator as above but rather than using a simple diode detector to view the output a spectrum analyzer is used as the detector. The spectrum analyzer will have a sensitivity in the range of -80 to - 100 dbm or so. With the sweep generator set for an output of zero dbm, you will be able to see the signal down to the -80 to -100 dbm level. The sweep generator operates in sync with the spectrum analyzer so that they are both on the same frequency at the same time. In other words they sweep the particular range of frequencies together. It is like using a tunable receiver and a tunable signal generator and moving them both with one hand on each tuning knob so as to move them together. A service monitor with just a sweep generator is usually not able to perform as a tracking generator because the monitor does not have the capability of generating and receiving simultaneously, which is a requirement for a tracking generator. A service monitor with a DUPLEX GENERATOR will have the ability to generate on one frequency and receive on another in order to test repeater operation. Some of those type monitors have a fixed signal generator level output in the duplex mode and some are adjustable in level. They may or may not have the capability to generate and receive on the same frequency at the same time which is required of a tracking generator. To function properly as a tracking generator they must also have sufficient isolation between the signal generator output and the spectrum analyzer input which some do not that are only intended for duplex operation and not specifically to function as a tracking generator. 73 Gary K4FMX
RE: [Repeater-Builder] Two Repeaters, One Antenna
Transmitter combiners are not always high loss, avoid like the plague kind of thing. 10 channels at 250 Khz spacing on 800 does give you quite a hit but it is still better than the alternative. The cavity on each transmitter must give at least 10 db of attenuation at the other frequencies in the combined system. So for close spaced frequencies the cavity insertion loss must be increased in order to obtain the proper skirt selectivity of the cavity so that 10 db can be met. With wider spacing there is much less insertion loss needed to obtain the required isolation. Also as frequency comes down, UHF or VHF the selectivity of the cavity gets better and less insertion loss is required for that same 10 db needed for isolation. So don't overlook transmitter combining as a high loss thing. It may not be. When spacing gets real close then hybrid combiners are needed and losses really get high there especially with several channels. These are quite common on 900 MHz and 220 MHz ACSB systems where channel spacing is very close. Sometimes combined channels can be split up with 2 antennas putting half the channels on each antenna and staggering their frequencies so you can use minimum loss. Also sometimes receive channels can be on those same antennas with 1 or 2 receiver multicouplers and appropriate filters. It all depends on what frequencies are involved. In regard to the two repeaters on one antenna, Jeff summed it up very well. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Jamey Wright Sent: Thursday, February 21, 2008 12:12 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Two Repeaters, One Antenna I agree with Ken. On an 800 Mhz system I maintain, 100 watts into the combiner yields about 16 watts at the antenna. This is a 10 channel combiner with 250khz spacing and 320 ft of 1 5/8 Heliax. We have actually installed a second antenna and feedline and have plans to split the combiner but just haven't gotten around to it yet. Kinda sucks but there's always a warm spot in the room in the winter. Jamey Wright Systems Analyst/EDACS Administrator Morgan County EMCD 911 Decatur, AL 256-552-0911 -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Ken Arck Sent: Thursday, February 21, 2008 10:51 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Two Repeaters, One Antenna At 08:43 AM 2/21/2008, you wrote: It can be done. I used to work with a UHF commercial system which combined multiple repeaters to a common antenna. The cans were built tuned by TxRx; rather expensive in terms of money and insertion loss. -One comment for what it's worth. Transmitter combiners are generally quite lossy. And that loss can increase to prohibitive amounts the closer in frequency adjacent ports are. In other words, there is a point of diminishing returns IMHO Ken -- President and CTO - Arcom Communications Makers of repeater controllers and accessories. http://www.arcomcontrollers.com/ Authorized Dealers for Kenwood and Telewave and we offer complete repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp.net We don't just make 'em. We use 'em! Yahoo! Groups Links Yahoo! Groups Links
RE: [Repeater-Builder] Re: Desense Problem on 222 MHz Repeater
I can't imagine why you would want to put a window filter between your duplexer and antenna line. There is much more to be gained by putting separate band pass filters on the tx and rx ports. In order to make a window filter you need several pass filters in order to make a wide window. Using those filters tuned to a single frequency is much more effective. A window filter is effective and commonly used if you have several receive frequencies that you are pulling off of one antenna and going to a multicoupler. There are times (rare) that a window filter may be used to pass several transmitters but off hand I can't think of one. There used to be a company or two that made VHF crystal filters that were used ahead of receivers to cure stubborn problems. They were quite expensive. I don't know if anyone still makes them. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Richard Sharp, KQ4KX Sent: Wednesday, January 30, 2008 9:06 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Desense Problem on 222 MHz Repeater Yeah, of course you'd want to order any filter optimized for your application. Yes, DCI markets products for the Amateur market but they also have a lot of products for commercial markets. I have indeed used some of their products (HAM commercial) and have had very good results. Hi-Q bandpass cavities is absolutely the best thing for frequency specific filtering between the TX RX ports of a duplexer and the transmitter receiver but a window filer is going to be more appropriate for the antenna side of the duplexer. DCI is not the only one out there that makes window filters either. If you're going to use split antennas a window filter would not be needed. As I think a couple of others have already mentioned a spectrum analyzer is a necessary tool in today's RF environment to make sure you're being a good RF neighbor as well as finding external sources of IMD too. Richard Nate Duehr wrote: Careful. I've looked over their product line and their stock filters have published SWR numbers that don't look good for high 147 and low 145 repeaters... they tend to be made for the center of the band for the end-users, not for repeaters. The skirts on even their 4 MHz wide filters start to roll off if your machines are at either end of the spectrum. Check carefully if you choose to use their filters, or call them and ask them if they'd tune them lower/higher (probably for a charge). Better yet, buy big, real, high-Q bandpass cavities and don't mess around with these little things made for hams at home. Nate WY0X Yahoo! Groups Links
RE: [Repeater-Builder] Re: Desense Problem on 222 MHz Repeater (window filter cannon fodder)
[EMAIL PROTECTED] On Behalf Of skipp025 (window filter cannon fodder) I can't imagine why you would want to put a window filter between your duplexer and antenna line. There is much more to be gained by putting separate band pass filters on the tx and rx ports. There can be good reasons for including a window filter with a duplexer. Reduction of high powered signals, which are IF Images would be one such appplication. Sometimes a plain jane duplexer just isn't enough. Sometimes a duplexer doesn't provide a DC return to ground, which is nice to have when/where possible. Let's not shoot ourselves in the foot here. :) If you need more selectivity for the transmitter or the receiver then put a cavity or two on the appropriate port. You get more for your money that way. If you want DC ground a shorted 1/4 wave stub does wonders. In order to make a window filter you need several pass filters in order to make a wide window. Any number of band-pass cavities can be a window filter even one. Actually a lot of different cavity types can be window filters. BpBr Cavities can and have been used as tx and rx window filters. One band pass cavity does not make for a window filter as the term window filter is commonly used. Yes a single cavity will pass two or more very close spaced frequencies but it isn't going to pass a tx and rx of a common 2 meter repeater with normal loss. Let's not stretch the term too far. Using those filters tuned to a single frequency is much more effective. I wouldn't put that in stone... It actually depends on the need and the application. A window filter is effective and commonly used if you have several receive frequencies that you are pulling off of one antenna and going to a multicoupler. One of the more commmon applications when the receive window band schemes work out... ie the UHF band most often when everything in the world is perfect... In most busy areas you'll rarely find the perfect world in any commercial and amateur band. Someone is always up to something funky... That's true enough. Sometimes several window filters are paralleled to include different segments of the band or a band pass cavity or two are paralleled to accommodate specific frequencies. There are times (rare) that a window filter may be used to pass several transmitters but off hand I can't think of one. ... in Antenna Combiner Systems where you must avoid mixing with other signals in the adjacent band(s). Also some other creative applications. In transmitter combiner systems individual cavities are usually placed at the output of each transmitter. Sometimes more than one cavity on each transmitter before going to the combine point. That provides the isolation needed between transmitters and the high power present at each and also affords some noise protection to others and to your own receivers. Placing a window filter after that has too many problems. There used to be a company or two that made VHF crystal filters that were used ahead of receivers to cure stubborn problems. They were quite expensive. I don't know if anyone still makes them. Piezo Technologies in Floriday, now using a new name of MTRONPTI http://www.mtronpti.com/ Yeah, they're expensive but they work fairly well for very pesky problems in the VHF Band, which are very hard to deal with with bottles (cavities) and wider pre-selectors ... with the corresponding insertion loss. Every filter and combiner part has multiple applications. You don't learn about some of the other options until the gremlins arrive. I have seen some guys do some really odd things at sites to make things work but doing it right is usually much more fruitful and less problems. 73 Gary K4FMX cheers, s. Yahoo! Groups Links
RE: [Repeater-Builder] Re: Desense Problem on 222 MHz Repeater (window filter cannon fodder)
_ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Daron Wilson Sent: Thursday, January 31, 2008 9:37 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Desense Problem on 222 MHz Repeater (window filter cannon fodder) I can't imagine why you would want to put a window filter between your duplexer and antenna line. There is much more to be gained by putting separate band pass filters on the tx and rx ports. There can be good reasons for including a window filter with a duplexer. Reduction of high powered signals, which are IF Images would be one such appplication. Sometimes a plain jane duplexer just isn't enough. Sometimes a duplexer doesn't provide a DC return to ground, which is nice to have when/where possible. Let's not shoot ourselves in the foot here. :) If you need more selectivity for the transmitter or the receiver then put a cavity or two on the appropriate port. You get more for your money that way. Perhaps.but not necessarily. We have a VHF system on a site that is very noisy and crowded. Separate transmit and receive antennas with about 100' of vertical separation. We worked with a variety of full size band pass and notch cans in different configurations but could never clear up some grunge in the receive side. I installed a DCI 144-148 Mhz window filter in the receive side before the cans and it shaped right up. Whatever was getting in was pretty much filtered by this additional window filter, and we hadn't been able to do it with three band pass filters. 73 N7HQR http://geo.yahoo.com/serv?s=97359714/grpId=104168/grpspId=1705063108/msgId= 79015/stime=1201832734/nc1=4025304/nc2=5028925/nc3=5170402
RE: [Repeater-Builder] Re: Desense Problem on 222 MHz Repeater (window filter cannon fodder)
Sorry my last response to this didn't come through. Additional may be the key word here. I can assure you that a window filter did not do the job just because it is a window filter. Pass cavities do not have ultimate rejection off frequency. The skirt goes down to a certain point and then levels out. Some worse than others. Pass cavities can also have spurious responses. Third harmonic energy will pass thru just as well as the fundamental will. Sometimes ultimate rejection at some point is more important than how sharp the filter is. Your window filter may have had better rejection at the interfering frequencies than the cavities did. But if that filter does the job for you that's good. I am only trying to point out when and where a window filter is appropriate. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Daron Wilson Sent: Thursday, January 31, 2008 9:37 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Desense Problem on 222 MHz Repeater (window filter cannon fodder) I can't imagine why you would want to put a window filter between your duplexer and antenna line. There is much more to be gained by putting separate band pass filters on the tx and rx ports. There can be good reasons for including a window filter with a duplexer. Reduction of high powered signals, which are IF Images would be one such appplication. Sometimes a plain jane duplexer just isn't enough. Sometimes a duplexer doesn't provide a DC return to ground, which is nice to have when/where possible. Let's not shoot ourselves in the foot here. :) If you need more selectivity for the transmitter or the receiver then put a cavity or two on the appropriate port. You get more for your money that way. Perhaps.but not necessarily. We have a VHF system on a site that is very noisy and crowded. Separate transmit and receive antennas with about 100' of vertical separation. We worked with a variety of full size band pass and notch cans in different configurations but could never clear up some grunge in the receive side. I installed a DCI 144-148 Mhz window filter in the receive side before the cans and it shaped right up. Whatever was getting in was pretty much filtered by this additional window filter, and we hadn't been able to do it with three band pass filters. 73 N7HQR http://geo.yahoo.com/serv?s=97359714/grpId=104168/grpspId=1705063108/msgId= 79015/stime=1201832734/nc1=4025304/nc2=5028925/nc3=5170402
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
How are you checking for desense? Are you using an isolated T between the duplexer and antenna line and doing the same when measuring desense on the dummy load? Are you measuring site noise? Do this the same way you would measure desense with the isolated T in the line. But first see what the receiver sensitivity is with the dummy load connected in place of the antenna. Then replace the dummy load with the antenna, do not key the transmitter, and measure the difference in receiver with the antenna connected verses the dummy load. With TV stations present you may be surprised at the amount of site noise present. Then key the transmitter and again measure receiver sensitivity thru the isolated T. If you haven't done this you may find that a lot of the problem is site noise rather than desense problems. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Stu Benner Sent: Friday, January 25, 2008 12:52 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense Problem on 222 MHz Repeater Our group has substantial technical knowledge and experience, but we've been just about beaten down by a problem with our repeater. A brief overview of our situation follows. We have a 222 MHz repeater comprised of a converted Micor mobile, Telewave TPRD-2254 BpBr duplexer, AM-6155 PA modified for class C operation at 250W, and a DB-264JJ antenna at 80 ft. fed by 1/2' Heliax on a commercial FM broadcast tower . With the duplexer terminated into a load, we have about 1 dB degradation in sensitivity when transmitting. However, with the antenna connected to the duplexer, we experience in excess 15 dB of desensitization. We have eliminated other narrowband transmitters and analog TV transmitters as contributing factors. We are left with a channel 12 digital TV transmitter at an adjacent site as a key contributor to the problem. Our hypothesis is that we have broadband IMD products from the mix of our transmitter and the DTV transmitter that are appearing in and near our receiver passband. Is it a rusty bolt problem or is there some other non-linear component somewhere on the site or in our system that is the mixing point - we don't know. I'd be interested in beginning a dialog with anyone who might be able to give us some further insight into this problem. Regards, Stu Benner W3STU Boonsboro, MD
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
If you have an extra band pass cavity then you also have a notch cavity. Just connect a T to one port of the band pass cavity and ignore the other port on the cavity. This will work as a notch cavity for your testing. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Stu Benner Sent: Friday, January 25, 2008 4:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater Thanks to everyone for the replies so far. Please see comments embedded below. I think that they address most of the comments, questions, and recommendations posed by all to this point. If you suspect IMD between the channel 12 DTV transmitter and your Tx carrier, work on attenuating the DTV signal. Using cavity notch filters to reject the entire 6 MHz of DTV isn't too practical, so instead, try adding pass cavities on your Tx before the duplexer input. That will help determine if the IM is originating in your PA. An isolator *may* help, but with channel 12 being the better part of 20 MHz away (about 10%), it may not afford full protection -- isolators don't have infinite bandwidth. Likewise, finding a 250 watt 220 MHz isolator may not be easy. I think I have some 220 isolators that came off a combiner (Sinclair), but doubt they're good for 250 watts judging by their size. [Stu] Agree, notches don't work well for that plus we don't have handy any cavities that will tune there. Have used up to two BP cavities in the TX path along with a 2-stage isolator. No difference in desense is observed. If you suspect a rusty bolt mix, use an alternate antenna for testing. If nothing else, try a quarter-wave whip (suitable for operation at your 250 watts TPO), even if it's just temporarily mounted on the tower (be sure it's at a sufficient height to prevent desense due to close proximity to the repeater itself). [Stu] We're presently on split antennas. One is at about 80 ft., the other is at about 15 ft. This improves the desense on the order of 6 dB. Another good possibility is IM in your receiver front end (or preamp, if you're using one). Again, pass cavities are your friend here. Attenuate the channel 12 signal as much as possible and see if it makes a difference. Have you looked at what sigs are reaching your receiver input on a spectrum analyzer? With 15 dB of desense, you should be able to see the culprit(s); it's not like they're going to be buried in the noise if it's causing 15 dB of desense. [Stu] The desense is significant with or without a preamp. Worse with but I can't find my notes to quote numbers. Used up to 2 BP cavities on RX with no perceptable difference in desense. Have also installed a DCI 4-pole filter on RX and TX with no effect. Have looked at the receiver input with a spectrum analyzer. The most significant signal is the one FM broadcast transmitter at the site. Running power down on it or turning it off has no effect on the desense. Our TX signal at our RX input is consistent with our measured duplexer isolation (about -88 dBc or -34 dBm). Within several hundred kHz of the RX frequency there are no detectable narrowband signals. Even that 1 dB of desense would give me some agita. I'd verify that the duplexers are properly tuned and the transmitter is clean before even starting down any other paths related to the channel 12 issue. IIRC, the Telewave cavities have adjustable coupling. If necessary, sacrifice a little extra loss for additional rejection if necessary. [Stu] I tuned the duplexer myself with a network analyzer and the transmitter looks clean. I have coupling set where I get about 1 dB through loss and the notches are at about 88 dB on TX and about 90 dB on RX. I also assume you're using all known-good interconnect cables (no foil+braid or other cables not suitable for duplex operation). [Stu] All cables are either Heliax or double braided. Are you using a Polyphaser or other type of surge arrestor? If so, try bypassing it. I've seen gas discharge tube type surge arrestors become noisemakers after absorbing a strike. [Stu] Yes but there is no difference in desense when it is removed. Has the VSWR changed at all on your antenna? If so, it could indicate water in a connector or the harness which will cause all kinds of grief, including wideband noise. [Stu] The problem has existed since the repeater was installed. It exists whether we duplex on a DB264 at 80 feet or a G7-220 at 15 feet, both fed with Heliax Finally, does the desense change appreciably if you vary transmitter power output (it probably will). Do you any have desense when running on just exciter power? [Stu] The desense is roughly proportional to transmit power. Barely perceptable at 20W (exciter only) with split antennas. A little worse at 20W (exciter only) using one antenna. Have tried both tube-type and solid state amplifiers at various power levels. --- Jeff WN3A
RE: [Repeater-Builder] Re: MSR2000 transmit spike
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Ken Arck Sent: Thursday, January 17, 2008 7:11 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: MSR2000 transmit spike At 04:06 PM 1/17/2008, you wrote: This sort of thing happens a lot when people do a tweak peak adjustment of an already working transmitter/exciter. Some stages are by default properly aligned first for a meter dip indication while others are peaked. --I'm still wondering how a low level signal 14 megs away from the passband of a duplexer (assuming it's a Bp/Br) can radiate any distance. Ken There is a lot of misunderstanding of Bp/Br duplexers. Just because it has the word band pass in the title doesn't mean that it is a good band pass device. If you look at the curves of most Bp/Br duplexers you will see that between the notch frequencies there is excellent band pass rejection because of the cumulative skirts of the filters in both sides of the duplexer in this area. However when you get on the outside of the notches there is little band pass effect and it is usually quite broad in respect to a true band pass filter. Also the ultimate rejection trails off too in most cases as you move farther away in frequency. As far as interference goes, either incoming or outgoing, it is all a matter of how much attenuation the filter devices are providing. As a note that may come in handy for someone chasing interference, you can use a pass band cavity as a notch cavity by just putting a T connector on one side and inserting it in line. Leave the other connection to the other loop blank. 73 Gary K4FMX
RE: [Repeater-Builder] Low Repeater output at site only
When inserting the bird meter between the duplexer and the radio make sure that you have a jumper that you use with the bird meter that makes the meter and jumper cable a 1/2 wavelength at the frequency of the transmitter. That way inserting the meter will show the transmitter the same impedance that it sees from the duplexer without the meter in the circuit. This is the jumper that you add along with the meter between the regular cable from the duplexer and the transmitter. The bird manual tells you how to calculate the jumper cable length to use. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Scott Zimmerman Sent: Wednesday, January 16, 2008 3:11 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Low Repeater output at site only Mike, I would strongly suspect the Mark IV is having problems. My experience with those repeaters has NOT been good. They seem to be VERY spooky. Especially when it comes to high RF environments. Most of these units were fine when they were first produced, but as the components age, they are becoming increasingly more problematic. Our local club had one since the early 80's. They dumped it in favor of a Micor conversion about 7 years ago and haven't looked back. Another local club still has theirs on the air. About the time our club got rid of ours, they decided to re-build theirs. Many hours and capacitors later, they had it working OK. Now, it's so deaf you have to run 50W 5 miles from the site to make an S5! If I were to hazard a guess at what your problem might be, I would guess it might be 2 things: 1. The PA drive control circuitry is interpreting the high RF at the site coming back down from the antenna to be reflected power and shutting the power amp down to keep from blowing it up. -- OR-- 2. The transmitter is spurring and the drive control is doing what it is supposed to do and shutting the transmitter back to keep from blowing it up. Do this: If you connect a dummy load and wattmeter to the duplexers instead of the antenna. Connect a wattmeter between the Tx and the duplexer . How many watts are coming from the Tx and how many watts do you have into the dummy load? Your duplexer loss should be less than 1/3. In other words if you have 30W from the PA, you should have more than 20W coming out of the duplexers into the dummy load. If not, you have duplexer trouble, or a spurious transmitter. I would then look at the transmitter on a spectrum analyzer and see how much 'grass' you are growing. Good luck, Scott Scott Zimmerman Amateur Radio Call N3XCC 612 Barnett Rd Boswell, PA 15531 - Original Message - From: k9mi [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, January 16, 2008 2:29 PM Subject: [Repeater-Builder] Low Repeater output at site only Sorry, this isn't actually a repeater-builder question, but it is a repeater problem, and this is where I thought I could get the best info for the problem. We have a Mark IV that has worked well for 9 years. It's really still working well, but here is what is going on. With a Bird watt meter, the Mark IV shows 3 watts out. If another member of the club, using the same meter and a dummy load, shows 32 watts (usual for the Mark IV). We also have a backup repeater, and Icom IC-RP1510 that has always had an output of 18 watts, and still does. It shows 18 watts out, 1 reflected, same as it always has. These output readings are before the duplexers (Wacom 641). The mystery is the Mark IV works fine into a dummy load, but not at the site. The Icom works the same as always. The a/c voltage (this is at a hospital) is 124 volts. It is a multi-transmitter site, and the MFJ analyzer shows our DB 224 as pegged on the swr, then it will drop briefly to a low SWR, and then go back up for a couple of minutes, and then drop again . I think the MFJ analyzer is just getting RF'ed from another transmitter, and that the Bird is much more reliable under these circumstances. The Icom with 18 watts out, 1 reflected leads me to believe the system is fine, but why would the Mark IV have an output of 3 watts into the Bird watt meter (nothing reflected), but into a dummy load, the Mark IV behaves as it should. My only other thoughts on testing would be to take a 50 watt 2m rig/ps and a different Vswr/wattmeter up and see how it behaves with the system. Any help/ideas would be appreciated. Tnx... 73, Mike K9MI [EMAIL PROTECTED] Yahoo! Groups Links -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.19.5/1228 - Release Date: 1/16/2008 9:01 AM Yahoo! Groups Links
RE: [Repeater-Builder] Revisiting Shorted 1/2-wave Traps
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Monday, January 14, 2008 11:21 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Revisiting Shorted 1/2-wave Traps -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Paul Plack Sent: Sunday, January 13, 2008 6:22 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Revisiting Shorted 1/2-wave Traps Paul, Curious who makes the RG-8M you have. Jeff, the cable is Tandy. In the '80's, the Tandy Wire Cable RG-8M was much better than their own full-sized RG-8, and they'd sell you 20' off the roll at the store. I used it in many mobile installations when there wasn't time to mail-order something better. This was a junkbox scrap with a PL259 on one end. I'm wondering if RG-8M is what we used to call marine mini-8. It's the same as RG-8X, but was often white in color. The jacket may have been something that tolerated the saltwater environment better? --- Jeff WN3A The only difference in what was called marine coax cable was that it was white rather than black. 73 Gary K4FMX
RE: [Repeater-Builder] Revisiting Shorted 1/2-wave Traps
Paul, You have to account for the velocity factor of the cable. The length you use has to be the electrical length not the physical length. This measurement that you made indicates that the cable is a quarter wave (not ½ wave) at 146.15 if indeed you do have the far end open. 146.15 MHz (Open 1/2-wave): R=3, X=1, SWR=12.0 (Z= about 3 ohms) Rules to remember: A shorted quarter wave reflects an infinite impedance at the other end. An open quarter wave reflects a short at the other end. A shorted half wave reflects a short at the other end. An open half wave reflects an open at the other end. A ¾ wave will act the same as a quarter wave. After all it is a quarter wave connected to a ½ wave. A short at one end reflects an open at the ¼ wave point which is the start of the ½ wave section. The ½ wave section is seeing an open so the other end of the half wave section will also be an open. A ½ wave line will always reflect the same the far end as it sees at the input end. A ½ wave line is the same as two ¼ wave lines connected together. An open at one end, a short in the middle and an open at the far end. An easy way to remember when considering an open or shorted stub: A quarter wave is always opposite and a half wave is the same. In measuring for a short or open it is easier to see with the mfj if you do not use a load. That way you will see a high impedance when you are at the ½ wave point rather than seeing 50 ohms. Either way you will see the short though. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Paul Plack Sent: Sunday, January 13, 2008 1:57 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Revisiting Shorted 1/2-wave Traps I'm posting this with all due respect to those who disagreed with an earlier post, and in the hopes of discovering any error I might be perpetuating. A few weeks ago, a member of the group was asking for help with interference on the input of a 900-MHz ham repeater from a co-located FM broadcast station. Among the possible remedies discussed were coaxial stub filters on the receiver's transmission line. One of the initial proposals was an open, 1/4-wave stub tuned for the FM broadcast frequency, fed on a coaxial T-connector. This is, indeed, a common method to trap a particular frequency. I set forth that this wouldn't work, as the desired pass frequency was too near the 9th harmonic of the trap, which means it, too, would be attenuated. (These traps are VERY wide when fed on a T-connector, and work at all odd harmonics of the fundamental.) The open 1/4-wave coax trap, sometimes called a suck-out trap, is best suited to a case in which the reject frequency is at least double the desired pass frequency, to avoid attenuation of the operating frequency itself. I proposed that better success might be achieved with a shorted, 1/2-wave stub tuned for the 900 MHz receive frequency, which would be nearly invisible at the 900 MHz pass frequency, but provide 20+ dB of attenuation at most frequencies below about 450 MHz. I did this based on experience not only using such shorted traps, but also after much past experimentation with my Wavetek sweep generator. Two subsequent posts took issue with my suggestion. One, from a member claiming engineering credentials, suggested my trap would appear as a dead short on the operating frequency, and that a shorted quarter-wave trap was the correct method. No supporting theory was offered. Another post suggested that a shorted 3/4-wave trap was correct, based on recollection of an instructor's comment. I've built and used several of these 1/2-wave traps, but it's been a few years, and I didn't want to dispute these comments until I'd gone back and made some actual measurements. I'd drop the matter, but this is too useful a technique to have it discredited unfairly. I still have the sweep generator, but not a scope, so I put my MFJ 259B analyzer, a 50-ohm dummy load, and a 41-inch piece of RG-8M (1/2-wave cut for 2m) on a T connector and look at SWR and impedance. Here are the resulting measurements of resistance, reactance, and SWR: 146.15 MHz (Shorted 1/2-wave): R=47, X=2, SWR=1.0 (Virtually unchanged from the dummy load alone) 73.08 MHz (Shorted 1/4-wave): R=23, X=20, SWR=2.4 (Z= about 31 ohms) 73.08 MHz (Open 1/4-wave): R=25, X=26, SWR=2.7 (Z= about 38 ohms) 146.15 MHz (Open 1/2-wave): R=3, X=1, SWR=12.0 (Z= about 3 ohms) 152.8 MHz (Open 1/2-wave): R=2, X=8, SWR=21.1 (Z= about 9 ohms. Note: This was the SWR peak, higher in frequency than the shorted frequency in part because the braid was folded back, instead of connected to the tip of the center conductor.) The readings at 146.15 MHz, coax shorted, were nearly identical with my 2m ground plane attached in place of the dummy load. Note that the only arrangement which looks like a dead short is the open 1/2-wave stub. The bandwidth of the shorted
RE: [Repeater-Builder] Re: Amplifier
Hi Chong, I am not exactly sure what the equipment is being used for? Is this a receive amplifier or for transmitters? How much power output do you get with just one signal applied to the amplifier? Will it produce +22dBm with one signal if the input level is increased? What is the gain of the amplifier? How many dB? Are you sure that the amplifier has capability to actually produce +22dBm of signal or is it speced at +22dBm 3rd order intercept point at 1 dB compression? If that is the case you will never see +22dBm out of it as the 3rd order intercept spec is only a theoretical projection point. You mentioned in an earlier post that you had 3 amplifiers in series. Is that still the case? What is the gain of each amplifier by itself? What is the power output capability of each amplifier? Are these receiver preamplifiers? 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Kent Chong Sent: Friday, January 11, 2008 3:55 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Amplifier Dear Gary, Thanks for the calculations. As we are using a +22dBm amplifier, the output per channel shall work out as -2dBm (+22dBm - 24dB, and +22dBm is 1dB compression point). However, the measurement shows that it is -24dBm per channel. Anything we have missed out? Best Regards, Chong Kwan Meng - Original Message From: Gary Schafer [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Friday, 11 January 2008 2:28:09 Subject: RE: [Repeater-Builder] Re: Amplifier If you want each signal, of the 16 signals, to be 0 dBm (1 mW) output capable then the amplifier has to be capable of 16 squared times 1 mW or 256 milliwatts. This is the peak envelope power that can be present at any one time in the amplifier with 16 signals present. So the amplifier would need to be able to handle a little over +24dBm with a single signal (256mW) With only 2 signals of 1 mW each the peak envelope power would be 2 squared (2x2) or 4 mW that the amplifier would need to handle or +6dBm. It is the number of signals squared times the power of one of the signals assuming that all the signal levels are the same. This is exactly the same thing as if it was an SSB linear amplifier and you were testing it with multiple tones. 73 Gary K4FMX _ From: Repeater-Builder@ yahoogroups. com [mailto:Repeater- [EMAIL PROTECTED] ups.com] On Behalf Of Kent Chong Sent: Thursday, January 10, 2008 8:46 PM To: Repeater-Builder@ yahoogroups. com Subject: Re: [Repeater-Builder] Re: Amplifier Dear NJ902, Thanks for your advise. In this case, what is the amplifier power rating for us to obtain 0dBm output power for 16 channels? Best Regards, Chong Kwan Meng - Original Message From: nj902 [EMAIL PROTECTED] net To: Repeater-Builder@ yahoogroups. com Sent: Friday, 11 January 2008 12:23:19 Subject: [Repeater-Builder] Re: Amplifier It appears that your amplifier is doing what you should expect. An amplifier's power handling capability, compression point, etc. are rated based on amplification of a single sinusoid. When multiple signals are present at the amplifier input, the total output power of the amplifier does not change, hence the power available per channel decreases as the number of input signals increases. Also, since multiple independent signals will combine randomly, crest factor issues further decrease the available power per channel in order to keep the amplifier output below clipping. This is a common issue in the design of signal enhancement products such as BDA's used to provide coverage extension for trunking and cellular radio systems. - - - - - - --- In Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups. com, Kent Chong kentchongkm@ ... wrote: All three amplifiers are connected in series. I shall correct my statement: in the lab, we get 0dBm output on the last stage of amplifier. However, when we are at the site, it max at -24dBm (it is - ve, sorry). There is no difference in the configuration but number of channel. _
RE: [Repeater-Builder] Re: Amplifier
If you want each signal, of the 16 signals, to be 0 dBm (1 mW) output capable then the amplifier has to be capable of 16 squared times 1 mW or 256 milliwatts. This is the peak envelope power that can be present at any one time in the amplifier with 16 signals present. So the amplifier would need to be able to handle a little over +24dBm with a single signal (256mW) With only 2 signals of 1 mW each the peak envelope power would be 2 squared (2x2) or 4 mW that the amplifier would need to handle or +6dBm. It is the number of signals squared times the power of one of the signals assuming that all the signal levels are the same. This is exactly the same thing as if it was an SSB linear amplifier and you were testing it with multiple tones. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Kent Chong Sent: Thursday, January 10, 2008 8:46 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Amplifier Dear NJ902, Thanks for your advise. In this case, what is the amplifier power rating for us to obtain 0dBm output power for 16 channels? Best Regards, Chong Kwan Meng - Original Message From: nj902 [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Friday, 11 January 2008 12:23:19 Subject: [Repeater-Builder] Re: Amplifier It appears that your amplifier is doing what you should expect. An amplifier's power handling capability, compression point, etc. are rated based on amplification of a single sinusoid. When multiple signals are present at the amplifier input, the total output power of the amplifier does not change, hence the power available per channel decreases as the number of input signals increases. Also, since multiple independent signals will combine randomly, crest factor issues further decrease the available power per channel in order to keep the amplifier output below clipping. This is a common issue in the design of signal enhancement products such as BDA's used to provide coverage extension for trunking and cellular radio systems. - - - - - - --- In Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups. com, Kent Chong kentchongkm@ ... wrote: All three amplifiers are connected in series. I shall correct my statement: in the lab, we get 0dBm output on the last stage of amplifier. However, when we are at the site, it max at -24dBm (it is - ve, sorry). There is no difference in the configuration but number of channel. _ Tired of visiting multiple sites for showtimes? Yahoo! http://sg.rd.yahoo.com/movies/*http:/sg.movies.yahoo.com/Showtimes/cinemas/ Movies is all you need
RE: [Repeater-Builder] Celwave 5042-1
I don't know that particular duplexer. The close spacing capability is not an indication that it is a band pass/band reject or a straight notch type unit. It could be either. The difference in the smaller mobile type or smaller rack mount type duplexers is usually in the insertion loss. The smaller the cavity the higher the insertion loss will be for a given set of operating parameters. It is usually not a problem getting enough rejection in the notch but it comes at the cost of higher insertion loss with the small cavities. The mobile type duplexers are usually notch only type and the other problem is that they usually have fixed capacitors in the internal loops that you can not change. So when you move them any great distance in frequency the insertion loss ends up even higher than the original spec because you can't change the loop capacitors. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Don Spivey Sent: Monday, January 07, 2008 2:51 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Celwave 5042-1 Has anyone had any experience with a Celwave 5042-1 duplexer? I've very skeptical of any rackmount VHF duplexer although specs on the 6 can version (this one) shows it capable of 500kc spacing at 100 watts. I've seen several of these in recent months and mow I'm getting curious. I haven't located tuning instructions either, and some of the Celwave mobile duplexers can be a bear to tune, so I've heard. For that spacing I would assume this must be a band pass/band reject design too...73 Thanks...N5MZQDon Yahoo! Groups Links
RE: [Repeater-Builder] VSWR Chart for Bird
1 + square root (r/f) SWR= _ 1 - square root (r/f) where r = reflected power f = forward power 73 Gary K4FMX from: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of n9wys Sent: Wednesday, October 31, 2007 6:07 PM To: Repeater-Builder@yahoogroups.com; [EMAIL PROTECTED] Subject: [Repeater-Builder] VSWR Chart for Bird Does anyone have a VSWR chart for the Bird wattmeter (preferably the 4410, since that's what I have - but I'm not sure there would be any difference) that they would be willing to share with me? I bought my meter used and it came with neither manual nor chart. Thanks, Mark - N9WYS
