[Repeater-Builder] Strange noise on our club repeater
We have a MSR2000 for our club repeater. Every so often on a weak signal we get a noise that sounds like...well you know when you go to the dentist and get your teeth cleaned. The little tube that they put in your mouth and sucks all the spit out. Wel... that is on the tail of some signals, sometimes. (sorry for the gross analogy ;-) This only happens a few times a day and not often on a stronger signal. When the user unkeys, it will have the sucking sound for a second or sometimes a few seconds...then the squelch closes. The user has unkeyed...but the repeater stays keyed up with the noise. We know that there are some strong signals near by the input. Also with the input at 144.61... there is a DStar repeater with a input of 144.60 up the road by 30 miles or so. Also... we have pretty fair amount of APRS traffic in the area (digi about 8 miles away). Ideas? Robert KD4YDC
Re: [Repeater-Builder] Strange noise on our club repeater
Sounds like intermod involving your repeater's transmitter as part of the mix. Chuck WB2EDV - Original Message - From: Robert kd4...@juno.com To: Repeater-Builder@yahoogroups.com Sent: Saturday, August 14, 2010 7:32 AM Subject: [Repeater-Builder] Strange noise on our club repeater We have a MSR2000 for our club repeater. Every so often on a weak signal we get a noise that sounds like...well you know when you go to the dentist and get your teeth cleaned. The little tube that they put in your mouth and sucks all the spit out. Wel... that is on the tail of some signals, sometimes. (sorry for the gross analogy ;-) This only happens a few times a day and not often on a stronger signal. When the user unkeys, it will have the sucking sound for a second or sometimes a few seconds...then the squelch closes. The user has unkeyed...but the repeater stays keyed up with the noise. We know that there are some strong signals near by the input. Also with the input at 144.61... there is a DStar repeater with a input of 144.60 up the road by 30 miles or so. Also... we have pretty fair amount of APRS traffic in the area (digi about 8 miles away). Ideas? Robert KD4YDC
RE: [Repeater-Builder] Coax length, etc.
Because the impedance is not matched between the transmitter and duplexer, the 'apparent' loss of the duplexer is greater than the manufacturers stated loss of the duplexer. Changing the cable length is not changing the loss of the duplexer, it's changing the power that is accepted at the transmitter port of the duplexer by matching the output impedance of the transmitter to the input impedance of the transmitter port of the duplexer. But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying the cable length isn't going to change the Z seen by the transmitter. Or are you suggesting the duplexer is purposely de-tuned from 50 ohms? And also that by varying the cable length between the transmitter and the duplexer that you can vary the reflected power on that same line? Yes. With all due respect, that's not possible, regardless of what the Z is of the duplexer. The only time it could have an effect on the reflected power would be if the transmitter/PA were spurious, and the amplitude/frequency of the spurs changed with varying load Z, and I think we can both agree that if that's the case, we have bigger fish to fry. Not to belabor the point, but whatever the VSWR is on a length of transmission line, that's the VSWR that's on the line *regardless of length*. You can't change the VSWR by changing the length of the line. As you vary the length, you go round n' round the Smith Chart in a constant VSWR circle, with the Z repeating cyclicly every half-wavelength, but you've still got a complex Z that nets a 1:5:1 VSWR relative to 50 ohms at the end of whatever length of line you choose (cable loss effects notwithstanding). There are an infinite number of complex Z's that yield a 1.5:1 VSWR - cut the line to any random length and you'll hit one of them. In a situation where the duplexer and transmitter have differing impedances, and a cable optimized in length matches these impedances, the mismatch at the duplexer is minimized, therefore the power reflected by the duplexer is minimized. I think what you're really saying is that the mismatch at the *input to the matching section* (i.e. the cable between the PA and the duplexer), NOT the mismatch at the duplexer, is minimized. The duplexer's input Z isn't changing; you can't change that unless you re-tune the cavities or change the load at the antenna port. Whether or that the transmitter likes/dislikes the different Z it sees as you change cable lengths is, I guess, what's up for debate... I have found that when you get a transmitter that is 'picky' about the length of interconnecting cable, power being read at the output port of the duplexer is low and you cannot alter the tuning of the cavity closest to the transmitter to make things right. In other words, the place where lowest VSWR and maximum power transfer occurs is at two completely different places, and power transfer is not up where it should be (transmitter makes 100 watts into a dummy load but only shows 50 watts on the output port of the duplexer that has a stated 1.5 dB loss (29 %)). That would imply that either duplexer is presenting a load Z substantially far removed from 50+j0, OR the transmitter doesn't like a 50 ohm load, or something inbetween, would it not? As you get close to the 'optimum' cable length, the lowest VSWR and maximum power transfer occur near the same place when tuning the cavity closest to the transmitter. But again, *you're NOT changing the VSWR*! You can't change the VSWR by varying the length of the line! I just want to make sure we're on the same page - the VSWR on a transmission line doesn't vary with length (loss notwithstanding). I usually pay more attention to what is coming out the antenna port of the duplexer - first. Then, when things are right, comparing forward power going to the duplexer and power going to a good dummy load will be very close the same, since matching the impedance of the transmitter to the impedance of the duplexer was accomplished by some means. Can you give me some real-world examples of what combinations of duplexers and transmitters you've run across that just didn't want to play nice without having to resort to changing cable lengths? Like a highband Micor 110 watt H split paired with a Q2220E or whatever. I'm just curious if I've done any of the same combinations. I think you know me well enough by now Kevin that I'm not looking to pick a fight, I'm just a hard-ass when it comes to basing technique on solid engineering foundation. I can't say I've ever had to play with cable lengths to either get a transmitter/PA to make rated power, or to get the apparent loss of a duplexer to meet spec. Have I just been lucky? Maybe. But if I'm *that* lucky, I'm in the wrong business, I shouldn't be sitting a hotel room in Harrisburg on a Saturday waiting for a tower crew to show up, I should be living the good life in Vegas
Re: [Repeater-Builder] Coax length, etc.
FWIW, TX/RX Systems talks about adverse length cable between the transmitter and the duplexer in their technical papers. Chuck WB2EDV - Original Message - From: Jeff DePolo j...@broadsci.com To: Repeater-Builder@yahoogroups.com Sent: Saturday, August 14, 2010 8:44 AM Subject: RE: [Repeater-Builder] Coax length, etc. Because the impedance is not matched between the transmitter and duplexer, the 'apparent' loss of the duplexer is greater than the manufacturers stated loss of the duplexer. Changing the cable length is not changing the loss of the duplexer, it's changing the power that is accepted at the transmitter port of the duplexer by matching the output impedance of the transmitter to the input impedance of the transmitter port of the duplexer. But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying the cable length isn't going to change the Z seen by the transmitter. Or are you suggesting the duplexer is purposely de-tuned from 50 ohms? And also that by varying the cable length between the transmitter and the duplexer that you can vary the reflected power on that same line? Yes. With all due respect, that's not possible, regardless of what the Z is of the duplexer. The only time it could have an effect on the reflected power would be if the transmitter/PA were spurious, and the amplitude/frequency of the spurs changed with varying load Z, and I think we can both agree that if that's the case, we have bigger fish to fry. Not to belabor the point, but whatever the VSWR is on a length of transmission line, that's the VSWR that's on the line *regardless of length*. You can't change the VSWR by changing the length of the line. As you vary the length, you go round n' round the Smith Chart in a constant VSWR circle, with the Z repeating cyclicly every half-wavelength, but you've still got a complex Z that nets a 1:5:1 VSWR relative to 50 ohms at the end of whatever length of line you choose (cable loss effects notwithstanding). There are an infinite number of complex Z's that yield a 1.5:1 VSWR - cut the line to any random length and you'll hit one of them. In a situation where the duplexer and transmitter have differing impedances, and a cable optimized in length matches these impedances, the mismatch at the duplexer is minimized, therefore the power reflected by the duplexer is minimized. I think what you're really saying is that the mismatch at the *input to the matching section* (i.e. the cable between the PA and the duplexer), NOT the mismatch at the duplexer, is minimized. The duplexer's input Z isn't changing; you can't change that unless you re-tune the cavities or change the load at the antenna port. Whether or that the transmitter likes/dislikes the different Z it sees as you change cable lengths is, I guess, what's up for debate... I have found that when you get a transmitter that is 'picky' about the length of interconnecting cable, power being read at the output port of the duplexer is low and you cannot alter the tuning of the cavity closest to the transmitter to make things right. In other words, the place where lowest VSWR and maximum power transfer occurs is at two completely different places, and power transfer is not up where it should be (transmitter makes 100 watts into a dummy load but only shows 50 watts on the output port of the duplexer that has a stated 1.5 dB loss (29 %)). That would imply that either duplexer is presenting a load Z substantially far removed from 50+j0, OR the transmitter doesn't like a 50 ohm load, or something inbetween, would it not? As you get close to the 'optimum' cable length, the lowest VSWR and maximum power transfer occur near the same place when tuning the cavity closest to the transmitter. But again, *you're NOT changing the VSWR*! You can't change the VSWR by varying the length of the line! I just want to make sure we're on the same page - the VSWR on a transmission line doesn't vary with length (loss notwithstanding). I usually pay more attention to what is coming out the antenna port of the duplexer - first. Then, when things are right, comparing forward power going to the duplexer and power going to a good dummy load will be very close the same, since matching the impedance of the transmitter to the impedance of the duplexer was accomplished by some means. Can you give me some real-world examples of what combinations of duplexers and transmitters you've run across that just didn't want to play nice without having to resort to changing cable lengths? Like a highband Micor 110 watt H split paired with a Q2220E or whatever. I'm just curious if I've done any of the same combinations. I think you know me well enough by now Kevin that I'm not looking to pick a fight, I'm just a hard-ass when it comes to basing technique on solid engineering foundation. I can't say I've ever had to play with
Re: [Repeater-Builder] Coax length, etc.
On 8/14/2010 8:44 AM, Jeff DePolo wrote: But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying the cable length isn't going to change the Z seen by the transmitter. Or are you suggesting the duplexer is purposely de-tuned from 50 ohms? I use a Network Analyzer to tune duplexers. Although I can usually get an impedance of 50 ohms, many times the L or C reactance is not perfect. Maybe the transmitter is responding more to the reactance mismatch rather than the impedance mismatch. This area of RF black magic very quickly gets me lost in the ether. 73, Joe, k1ike
RE: [Repeater-Builder] unsubscribe
It appears to work too. I have to be honest it is very hard to see it at the bottom of the messages. Maybe that could help it some to find it. Kenneth Cook, W8DZN _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Richard Sent: Saturday, August 14, 2010 12:35 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] unsubscribe Well, I think it's funny. Richard, N7TGB www.n7tgb.net The problem with socialism is that eventually you run out of other people's money --Margaret Thatcher _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kenneth Cook Sent: Friday, August 13, 2010 9:27 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] unsubscribe This is an experiment to see if I could make the link stand out. This is NOT to start problems! 73.de Ken Cook, W8DZN http://groups.yahoo.com/;_ylc=X3oDMTJjdHNidXRtBF9TAzk3NDc2NTkwBGdycElkAzEwN DE2OARncnBzcElkAzE3MDUwNjMxMDgEc2VjA2Z0cgRzbGsDZ2ZwBHN0aW1lAzEyODE3NDg1NTI- Yahoo! Groups Switch to: mailto:repeater-builder-traditio...@yahoogroups.com?subject=change%20delive ry%20Format:%20Traditional Text-Only, mailto:repeater-builder-dig...@yahoogroups.com?subject=email%20delivery:%20 Digest Daily Digest . mailto:repeater-builder-unsubscr...@yahoogroups.com?subject=unsubscribe Unsubscribe . http://docs.yahoo.com/info/terms/ Terms of Use . http://geo.yahoo.com/serv?s=97359714/grpId=104168/grpspId=1705063108/msgId= 102749/stime=1281748552/nc1=4025291/nc2=5191952/nc3=6083913
[Repeater-Builder] HYT Repeater vs. Trbo Repeater
Has anyone done any comparison testing between the HYT Repeater and The Motorola Trbo repeater? I am particulary interested in making a future purchase of either one. I have read about the IPsec concerns and that to me is really not an issue. I am sure that HYT will address that concern as time goes forward. From what I have been told, the Trbo consists of 2 mobile radios used for receive and the other for transmit. Whereas, HYT is one radio with a Duplexed receiver and transmitter well isolated from each other. It is also my understanding that the company HYT's vendors are more user friendly in pricing and support compared to Motorola when it comes to accessories, firmware updates and programming. Thanks in advance for any information. Artie k2aau
[Repeater-Builder] Re: Wanted - UHF Amplifier
Larry: I am using a version 2 TKR 850 with an Angle Linear GAas Fet Pre-amp with a bandpass cavity. Exc results without desense. The preamp is before the cavity. As I agree with the other writers, you will need to retune the receiver for optimum performance. Invest in a Good Commercial Antenna is key. Don't waste your money on a Ham Antenna as I learned not too long ago. Huge difference in performance! Good Luck! Artie k2aau --- In Repeater-Builder@yahoogroups.com, k7...@... wrote: Larry, Last week there was someone trying to sell several Henry UHF amps on the list. You may want to check your email box. Mike Mullarkey K7PFJ 6886 Sage Ave Firestone, Co 80504 303-736-9693 _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Larry Watkinson Sent: Monday, July 19, 2010 12:11 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Wanted - UHF Amplifier K5In and I are looking for a couple of UHF Amplifier's that will have 10 to 25 watts in and 70 to 100 watts out. We would prefer n-connectors but will accept other connectors. Thanks, Larry KC7CKO
Re: [Repeater-Builder] unsubscribe
I think that stands out :D Regards, -Frank C. On Aug 13, 2010, at 9:26 PM, Kenneth Cook wrote: This is an experiment to see if I could make the link stand out. This is NOT to start problems! 73…de Ken Cook, W8DZN Switch to: Text-Only, Daily Digest • Unsubscribe • Terms of Use .
Re: [Repeater-Builder] Re: Sorry everyone
oh i know that it wasnt sent from any of the computers that the YL or myself use nor was it sent through the local networks both here and at my house. i am of the belief that both of us were fished while on the laptop i bought for mom. i thought i installed spybot SD but i guess not. as soon as i can get her off of Farmville for a few minutes i will fix that. thanks again everyone. Dave E Stephens Sr KF6WJA Grants Pass Or --- On Fri, 8/13/10, Bob - AF6D b...@af6d.com wrote: From: Bob - AF6D b...@af6d.com Subject: [Repeater-Builder] Re: Sorry everyone To: Repeater-Builder@yahoogroups.com Date: Friday, August 13, 2010, 4:51 PM I haven't read all of the relies on this, but I also haven't read that there is proof that your computer actually sent the messages. All that is needed is your email address int he reply-to field in the message header and you get the blame. I own and operate a mid-sized web hosting company and we deal with spam issues daily. Recipients running anti-spam software that rejects and sends back to the real sender actually end up causing backscatter and getting their own IP blacklisted. SPAM will never end... --- In Repeater-Builder@yahoogroups.com, Dave E Stephens Sr kf6...@... wrote: i would like to thank all of you for understanding. right after i sent out my original appology i figured out which computer might be sending the cause of this. not long ago i got mom a new HP laptop. She wanted a computer just so she could play a few games. well mom is what i call a techno-tard (didnt even know how to turn it on). Before i knew it, her friend got her on facebook playing farmville and who knows what. Its the WHO KNOWS WHAT that i am worried about.  not long ago the YL was over there on the computer, checking her email. next day i discovered her account sent out a similar email to what mine sent. i used it the day before yesterday and BAM, i discover the same email sent out.  There is no evidence of a message being sent in my sent box here on Yahoo BUT i got 2 replys saying they couldnt be delivered.  I was going to fix the issue yesterday but i got busy. AVG and Spybot SD will be installed a little later on today.  You know, its funny... i spend 8 to 12 hours a day, 6 to 7 days a week, dealing with this issue and others like that. For 16 years i have never had an account of mine hit till now. i am supprised it didnt hit sooner.  Thanks again everyone for understanding... 73's  Dave Stephens Sr KF6WJA Grants Pass Or    --- On Thu, 8/12/10, Mark Tomany n9...@... wrote: From: Mark Tomany n9...@... Subject: Re: [Repeater-Builder] Sorry everyone To: Repeater-Builder@yahoogroups.com Date: Thursday, August 12, 2010, 6:51 AM  AVG Free anti-virus software also has a built-in spyware removal tool. I also use the ones George captioned below - and even I get bit every once in a while by some new bug.  It's amazing that so many people have the time on their hands to be able to propagate all this crap...  Mark - N9WYS --- On Wed, 8/11/10, George Henry wrote: Nonsense! Spybot Search Destroy, Ad-Aware, Malwarebytes Anti-Malware, and SuperAntiSpyware are all EXCELLENT free anti-spyware programs. I routinely use all 4 of them to clean up infections for people. No spyware in ANY of them and, between the four programs, I have yet to run into something I couldn't clean. George, KA3HSW / WQGJ413 - Original Message - From: Tim Sawyer Was your machine on while you were away? If so you may have gotten a virus or spyware. Sounds like your wife got it too. Spamers like to infect machines just to get control of them for sending spam. The really bad news is that most free spyware removal software is spyware itself. A really good PC guy might be able to remove it. Good luck man! -- Tim
[Repeater-Builder] Re: Wanted - UHF Amplifier
Larry: I am using a version 2 TKR 850 with an Angle Linear GAas Fet Pre-amp with a bandpass cavity. Exc results without desense. The preamp is before the cavity. As I agree with the other writers, you will need to retune the receiver for optimum performance. Invest in a Good Commercial Antenna is key. Don't waste your money on a Ham Antenna as I learned not too long ago. Huge difference in performance! Good Luck! Artie k2aau --- In Repeater-Builder@yahoogroups.com, k7...@... wrote: Larry, Last week there was someone trying to sell several Henry UHF amps on the list. You may want to check your email box. Mike Mullarkey K7PFJ 6886 Sage Ave Firestone, Co 80504 303-736-9693 _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Larry Watkinson Sent: Monday, July 19, 2010 12:11 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Wanted - UHF Amplifier K5In and I are looking for a couple of UHF Amplifier's that will have 10 to 25 watts in and 70 to 100 watts out. We would prefer n-connectors but will accept other connectors. Thanks, Larry KC7CKO
[Repeater-Builder] Re: unsubscribe
Your best bet is to setup your email to receive each post in digest form meaning once a day on average you will receive a bunch of postings in just one email into your inbox. When you get around to opening up your inbox you can just scroll through each individual posting, read the ones that interest you and when finished, hit the delete key and they all go away!!! Seeing 15-30 separate, individual emails in my inbox during the course of one day is a bit too much. Try it, you'll like it OM!!73 --- In Repeater-Builder@yahoogroups.com, Jim in Waco WB5OXQ wb5...@... wrote: I do not need to read these anymore. I am not mad just getting too many emails.
[Repeater-Builder] Re: HYT Repeater vs. Trbo Repeater
Hi Artie, Regardless of what make and model repeater equipment you choose, be sure to actually check the receiver discriminator output performance. I traced problems in a system running LTR and DCS Data back to one model of lower priced desktop repeater receiver. (also known as a two mobiles made into a repeater). The receiver discriminator output was just horrible for any type of data output. I replaced the low cost receiver (the entire repeater actually) with a Kenwood TKR-850 (I sold them) and their LTR/DCS system now works mucho great. CTCSS operation is relatively easy to implement but reliable data requires a faithful receiver discriminator output. Or make sure you have the ability to return the equipment if it doesn't pass the technical muster (requirements) cheers, skipp k2aau k2...@... wrote: Has anyone done any comparison testing between the HYT Repeater and The Motorola Trbo repeater? I am particulary interested in making a future purchase of either one. I have read about the IPsec concerns and that to me is really not an issue. I am sure that HYT will address that concern as time goes forward. From what I have been told, the Trbo consists of 2 mobile radios used for receive and the other for transmit. Whereas, HYT is one radio with a Duplexed receiver and transmitter well isolated from each other. It is also my understanding that the company HYT's vendors are more user friendly in pricing and support compared to Motorola when it comes to accessories, firmware updates and programming. Thanks in advance for any information. Artie k2aau
[Repeater-Builder] Re: Coax length, etc. GE Z-Matcher
--- In Repeater-Builder@yahoogroups.com, Jeff DePolo j...@... wrote: c) Although not explictly described in GE's tuning procedures, significant improvement in efficiency can be obtained with proper tuning of the Z-matcher. Tuning for 50+j0 at the input to the Z-matcher is NOT necessarily the RIGHT match! Right, GE's instructions on tuning the Z-Matcher in their base stations are not correct. Instructions should instead describe a procedure that reduces current draw of the amplifier while simultaneously maintaining or increasing the output power. d) To charge more. I'm half-joking on this; I can't say I've statistically seen more or less failures on M2 PA's with or without the Z-matcher, so I'll give this answer half a smiley: .-, If the failures you've seen are in amps with Z-Matchers that were tuned following GE's Z-Matcher instructions, that *could* explain why you've given half a smiley... :-) Laryn K8TVZ
[Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)
You guys are silly... Consider changing your group settings to read on the web using a web browser. Then... simply locate the group with your web browser bookmark anytime you want to read the group posts. No flood of inbound Emails for each post or large digest Emails required. Probably drive one to drink (more) if they were subscribed to more than 3 or 4 Groups at one time. Having a yahoo email address automatically signs me into all the groups for which I am subscribed. To read this, the Repeater Builder Group I simply click on the below Bookmark saved in my Web Browser. Once you change your settings to web only (I prefer the traditional or classic view) try the below url and enjoy life again. http://groups.yahoo.com/group/Repeater-Builder/messages If you don't use Yahoo Mail, you might be asked to sign in at the start of your web browsing session, but once you're in, you are in for all the groups for which you subscribe. cheers, s. ps: If you're subscribed to more than one group, here's the page that helps you get your book marks set up. http://groups.yahoo.com/mygroups Now resume normal programming. Your best bet is to setup your email to receive each post in digest form meaning once a day on average you will receive a bunch of postings in just one email into your inbox. When you get around to opening up your inbox you can just scroll through each individual posting, read the ones that interest you and when finished, hit the delete key and they all go away!!! Seeing 15-30 separate, individual emails in my inbox during the course of one day is a bit too much. Try it, you'll like it OM!!73 --- In Repeater-Builder@yahoogroups.com, Jim in Waco WB5OXQ wb5oxq@ wrote: I do not need to read these anymore. I am not mad just getting too many emails.
Re: [Repeater-Builder] Coax length, etc.
Jeff DePolo wrote: Because the impedance is not matched between the transmitter and duplexer, the 'apparent' loss of the duplexer is greater than the manufacturers stated loss of the duplexer. Changing the cable length is not changing the loss of the duplexer, it's changing the power that is accepted at the transmitter port of the duplexer by matching the output impedance of the transmitter to the input impedance of the transmitter port of the duplexer. But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying the cable length isn't going to change the Z seen by the transmitter. Or are you suggesting the duplexer is purposely de-tuned from 50 ohms? Purposely, accidentally, by lack of good design - people not having the right equipment to tune it correctly - whatever. And also that by varying the cable length between the transmitter and the duplexer that you can vary the reflected power on that same line? Yes. With all due respect, that's not possible, regardless of what the Z is of the duplexer. The only time it could have an effect on the reflected power would be if the transmitter/PA were spurious, and the amplitude/frequency of the spurs changed with varying load Z, and I think we can both agree that if that's the case, we have bigger fish to fry. And this is where I believe the duplexer manufacturers are covering their butt. They don't want the problem with complex reactance presented by the duplexer to be their problem. Not that I don't agree, because it's usually the transmitter that is really at fault. Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II repeater and gets 50 watts out the antenna port. He does his homework and realizes that he should only be loosing 29% with the 1.5 dB of insertion loss stated in the paperwork - but he's loosing over 50%. The duplexer manufacturer supposedly engineered and tuned it for a 50 Ohm system. He knows that the cable he connected to the transmitter is good, because when he disconnects the end going to the transmitter port of the duplexer and connects it to his Bird 43 terminated with a good load - it reads 110 watts. Now, is the transmitter becoming spurious and the cable length being changed in length satisfies the match between the duplexer and transmitter - I don't know... All I can tell you is I have followed the suggestions written in the WACOM manual and it has worked. I had one instance of a ham radio club loosing PA's left and right on their 2M machine. They told me of the situation and I offered to do a little testing. The 110 watt PA would put out 110 watts into a Bird and dummy, but only 45 watts was coming out the antenna port of the duplexer. At the time I didn't own a spectrum analyzer. The repeater wouldn't duplex without desense. I changed the length of the line between the PA and duplexer until I got the power to read about 75 Watts as I remember. That was 13 years and they still have the same PA - no desense either. Not to belabor the point, but whatever the VSWR is on a length of transmission line, that's the VSWR that's on the line *regardless of length*. You can't change the VSWR by changing the length of the line. As you vary the length, you go round n' round the Smith Chart in a constant VSWR circle, with the Z repeating cyclicly every half-wavelength, but you've still got a complex Z that nets a 1:5:1 VSWR relative to 50 ohms at the end of whatever length of line you choose (cable loss effects notwithstanding). There are an infinite number of complex Z's that yield a 1.5:1 VSWR - cut the line to any random length and you'll hit one of them. In a situation where the duplexer and transmitter have differing impedances, and a cable optimized in length matches these impedances, the mismatch at the duplexer is minimized, therefore the power reflected by the duplexer is minimized. I think what you're really saying is that the mismatch at the *input to the matching section* (i.e. the cable between the PA and the duplexer), NOT the mismatch at the duplexer, is minimized. Sorry - that is what I meant to say. Many of us use converted commercial gear in the ham band. Many don't take the time to properly convert the receiver and especially the transmitter to properly operate in the adjacent ham band. So, when you run a 150.8 to 174 MHz amplifier in the 2M ham band or a 450 to 470 MHz amplifier in the UHF ham band is it going to represent a good 50 Ohm impedance? Likely not... We need to realize that most duplexer manufacturers know what they are doing and their products are presenting a 50 ohm match on its intended frequencies - unless somebody has adjusted on it. But, because the duplexer is not a perfect load, it creates reactance and the transmitter/PA may not like it. If it doesn't like it, it may become spurious. If it becomes spurious, it isn't putting out all of its power
RE: [Repeater-Builder] Re: Coax length, etc. GE Z-Matcher
HOLY CRAP I've been wondering that for some time. Guess the manual isn't always right. and maybe that's why the GE Z-match is there for the recruiting of true GE tuners.. Never-mind keeping your PA happy at 100% DC. I always wanted to ask but never did (for thought of flames from the GE manual) because I thought I heard somewhere that tuning procedure wasn't ideal for most cavity/duplexer applications (on this list in a unrelated post) so investigated. Now I always settled for the best low ratio of the two. PA current/TP1 from z-match. You'll see that the relationship of the two is not even close to linear. What I've found is you basically want to try to be on the edge of both curves knee's.. I think I have the right idea, for a 50mV gain from the TP1 z-match null I could drop PA current by 2500mA. And this was until now (a month ago) that I finally have a good HP8924 SM to help take the guess work out. Plus your PA and TX cavity temps go way down. Just glad to hear I was probably doing the right thing. Also I always did the final 1st 2nd pass cavity tuning this way. Retuning cavities for highest output power with least current vs. low TP1 on z-match. One tuning session on a friends machine with this method dropped TX cavity temps by more then 10deg to almost ambient temp while dropping PA temp, and current by 2 amps with no drop in output power or RX sense. This probably means the match in the cavity coupling or cabling was off but hey that PA will live longer. If I'm wrong or missing something here, let me know. 73's groupies Ross www.kc7rjk.net http://www.kc7rjk.net/ -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of larynl2 Sent: Saturday, August 14, 2010 8:17 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Coax length, etc. GE Z-Matcher --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com , Jeff DePolo j...@... wrote: c) Although not explictly described in GE's tuning procedures, significant improvement in efficiency can be obtained with proper tuning of the Z-matcher. Tuning for 50+j0 at the input to the Z-matcher is NOT necessarily the RIGHT match! Right, GE's instructions on tuning the Z-Matcher in their base stations are not correct. Instructions should instead describe a procedure that reduces current draw of the amplifier while simultaneously maintaining or increasing the output power. d) To charge more. I'm half-joking on this; I can't say I've statistically seen more or less failures on M2 PA's with or without the Z-matcher, so I'll give this answer half a smiley: .-, If the failures you've seen are in amps with Z-Matchers that were tuned following GE's Z-Matcher instructions, that *could* explain why you've given half a smiley... :-) Laryn K8TVZ
Re: [Repeater-Builder] Coax length, etc.
Kevin Custer wrote: Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II repeater and gets 50 watts out the antenna port. He does his homework and realizes that he should only be loosing 29% Wow -* loosing -* that should have been losing - that's what I get for being in a hurry
Re: [Repeater-Builder] Coax length, etc.
Kevin Custer wrote: I had one instance of a ham radio club loosing PA's left and right on their 2M machine. Indeed - I am loosing my mind - grin K
Re: [Repeater-Builder] Re: Wanted - UHF Amplifier
DB-420's are about as good as they get. I like the big blue Telewave's, but so does lightening if you are on top of the tower. - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Sat Aug 14 09:02:42 2010 Subject: [Repeater-Builder] Re: Wanted - UHF Amplifier Larry: I am using a version 2 TKR 850 with an Angle Linear GAas Fet Pre-amp with a bandpass cavity. Exc results without desense. The preamp is before the cavity. As I agree with the other writers, you will need to retune the receiver for optimum performance. Invest in a Good Commercial Antenna is key. Don't waste your money on a Ham Antenna as I learned not too long ago. Huge difference in performance! Good Luck! Artie k2aau --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com , k7...@... wrote: Larry, Last week there was someone trying to sell several Henry UHF amps on the list. You may want to check your email box. Mike Mullarkey K7PFJ 6886 Sage Ave Firestone, Co 80504 303-736-9693 _ From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of Larry Watkinson Sent: Monday, July 19, 2010 12:11 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Wanted - UHF Amplifier K5In and I are looking for a couple of UHF Amplifier's that will have 10 to 25 watts in and 70 to 100 watts out. We would prefer n-connectors but will accept other connectors. Thanks, Larry KC7CKO
RE: [Repeater-Builder] Coax length, etc.
Kevin, Don't feel bad- look at the number of postings that use you instead of your, your instead of you're, mhz instead of MHz, Khz instead of kHz, it's instead of its... the list is endless! But, back to the thread... it's refreshing to see that more than a few list members know that a dummy load is purely resistive, while a duplexer cavity is reactive- explaining why a transmitter that works perfectly when feeding a dummy load can be unstable when connected to a duplexer. This discussion is both informative and quite entertaining! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin Custer Sent: Saturday, August 14, 2010 10:15 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Coax length, etc. Kevin Custer wrote: Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II repeater and gets 50 watts out the antenna port. He does his homework and realizes that he should only be loosing 29% Wow - loosing - that should have been losing - that's what I get for being in a hurry
RE: [Repeater-Builder] Coax length, etc.
So will someone post a simple rule of thumb. If you have the option of optimizing cable length from PA to first cavity, IE you haven't made them yet what's the best simple rule of thumb to follow to build them to avoid reactance. 1/2wl if allowed minus coupling loop depth? Or is that past a simple thumb. Also, This will obviously not work well for 220 or 440 or a most vhf repeater setups. So what would the next ideal cable wl be? And so forth. The reason I ask, if your building new cables why not? Answers on here seem to range a lot. Ross kc7rjk
RE: [Repeater-Builder] Coax length, etc.
FORGOT to multiply cable VF then subtract coupling loop depth!!! Forgive me :-) -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Ross Johnson Sent: Saturday, August 14, 2010 11:59 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Coax length, etc. So will someone post a simple rule of thumb. If you have the option of optimizing cable length from PA to first cavity, IE you haven't made them yet what's the best simple rule of thumb to follow to build them to avoid reactance. 1/2wl if allowed minus coupling loop depth? Or is that past a simple thumb. Also, This will obviously not work well for 220 or 440 or a most vhf repeater setups. So what would the next ideal cable wl be? And so forth. The reason I ask, if your building new cables why not? Answers on here seem to range a lot. Ross kc7rjk
Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)
I am subscribed to all of my groups in 'single e-mail' form. I have configured Thunderbird to sort those groups into individual folders. By doing this, I can look at things in a digest mode. If I want to get rid of a bunch at one clip, I can select all and hit delete. Just my 2c worth of ideas. Scott Scott Zimmerman Amateur Radio Call N3XCC 474 Barnett Road Boswell, PA 15531 skipp025 wrote: You guys are silly... Consider changing your group settings to read on the web using a web browser. Then... simply locate the group with your web browser bookmark anytime you want to read the group posts. No flood of inbound Emails for each post or large digest Emails required. Probably drive one to drink (more) if they were subscribed to more than 3 or 4 Groups at one time. Having a yahoo email address automatically signs me into all the groups for which I am subscribed. To read this, the Repeater Builder Group I simply click on the below Bookmark saved in my Web Browser. Once you change your settings to web only (I prefer the traditional or classic view) try the below url and enjoy life again. http://groups.yahoo.com/group/Repeater-Builder/messages If you don't use Yahoo Mail, you might be asked to sign in at the start of your web browsing session, but once you're in, you are in for all the groups for which you subscribe. cheers, s. ps: If you're subscribed to more than one group, here's the page that helps you get your book marks set up. http://groups.yahoo.com/mygroups Now resume normal programming. Your best bet is to setup your email to receive each post in digest form meaning once a day on average you will receive a bunch of postings in just one email into your inbox. When you get around to opening up your inbox you can just scroll through each individual posting, read the ones that interest you and when finished, hit the delete key and they all go away!!! Seeing 15-30 separate, individual emails in my inbox during the course of one day is a bit too much. Try it, you'll like it OM!!73 --- In Repeater-Builder@yahoogroups.com, Jim in Waco WB5OXQ wb5oxq@ wrote: I do not need to read these anymore. I am not mad just getting too many emails. Yahoo! Groups Links
Re: [Repeater-Builder] unsubscribe
What link? From: Richard gbis-reply-...@gbis.com To: Repeater-Builder@yahoogroups.com Sent: Fri, August 13, 2010 11:35:07 PM Subject: RE: [Repeater-Builder] unsubscribe Well, I think it's funny. Richard, N7TGB www.n7tgb.net The problem with socialism is that eventually you run out of other people's money --Margaret Thatcher From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kenneth Cook Sent: Friday, August 13, 2010 9:27 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] unsubscribe This is an experiment to see if I could make the link stand out. This is NOT to start problems! 73…de Ken Cook , W8DZN Switch to: Text-Only, Daily Digest • Unsubscribe• Terms of Use .
Re: [Repeater-Builder] Coax length, etc.
That's because there are as many rules as there are thumbs. ;-) I don't know about anyone else, but I can tell you about the highly scientific method I use. I start with a multiple of 1/2 electrical wavelength and trim as necessary. I'd stay away from an odd-multiple of 1/4 wavelength in this application... no good reason, just because (black magic and all that). Try cutting the transmitter-to-duplexer line using the receive frequency length, and vice versa. If that doesn't work out, you can swap them. I know, on a 2m amateur system, the length difference is about 1/4. In that case, make a cable 1-2 shorter and see what happens. An alternative is to use multiple short lengths of coax connected together to find a happy length, then replace with a single coax cut to that length. As I said, highly scientific. :-P 73, Russ WB8ZCC On 8/14/2010 2:59 PM, Ross Johnson wrote: So will someone post a simple rule of thumb... If you have the option of optimizing cable length from PA to first cavity, IE you haven't made them yet what's the best simple rule of thumb to follow to build them to avoid reactance. 1/2wl if allowed minus coupling loop depth? Or is that past a simple thumb. Also, This will obviously not work well for 220 or 440 or a most vhf repeater setups. So what would the next ideal cable wl be? And so forth... The reason I ask, if your building new cables why not? Answers on here seem to range a lot... Ross kc7rjk
Re: [Repeater-Builder] Coax length, etc.
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 On 8/14/2010 12:53 PM, Kevin Custer wrote: Jeff DePolo wrote: Because the impedance is not matched between the transmitter and duplexer, the 'apparent' loss of the duplexer is greater than the manufacturers stated loss of the duplexer. Changing the cable length is not changing the loss of the duplexer, it's changing the power that is accepted at the transmitter port of the duplexer by matching the output impedance of the transmitter to the input impedance of the transmitter port of the duplexer. But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying the cable length isn't going to change the Z seen by the transmitter. Or are you suggesting the duplexer is purposely de-tuned from 50 ohms? Purposely, accidentally, by lack of good design - people not having the right equipment to tune it correctly - whatever. And also that by varying the cable length between the transmitter and the duplexer that you can vary the reflected power on that same line? Yes. With all due respect, that's not possible, regardless of what the Z is of the duplexer. The only time it could have an effect on the reflected power would be if the transmitter/PA were spurious, and the amplitude/frequency of the spurs changed with varying load Z, and I think we can both agree that if that's the case, we have bigger fish to fry. And this is where I believe the duplexer manufacturers are covering their butt. They don't want the problem with complex reactance presented by the duplexer to be their problem. Not that I don't agree, because it's usually the transmitter that is really at fault. Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II repeater and gets 50 watts out the antenna port. He does his homework and realizes that he should only be loosing 29% with the 1.5 dB of insertion loss stated in the paperwork - but he's loosing over 50%. The duplexer manufacturer supposedly engineered and tuned it for a 50 Ohm system. He knows that the cable he connected to the transmitter is good, because when he disconnects the end going to the transmitter port of the duplexer and connects it to his Bird 43 terminated with a good load - it reads 110 watts. Now, is the transmitter becoming spurious and the cable length being changed in length satisfies the match between the duplexer and transmitter - I don't know... All I can tell you is I have followed the suggestions written in the WACOM manual and it has worked. I had one instance of a ham radio club
[Repeater-Builder] Re: Fs: (/\/\)otorola UHF Desktrac
Um Ok, I want this gone. Tried swapping it, and selling it so how low do i have to go before someone will bite. not that i will necessarily let it go extremely cheap, but i am just curious about how low i have to go to get it sold. also want to know the reasoning of why it is so hard to get it sold since GMRS and Ham are still wideband. i will also toss in a small cushcraft uhf ringo as well. again will swap to a rebandable p25 mobile scanner or ??? here are pic's http://img405.imageshack.us/i/sales8910018.jpg/ http://img188.imageshack.us/i/sales8910017.jpg/ http://img842.imageshack.us/i/sales8910016.jpg/ http://img683.imageshack.us/i/sales8910015.jpg/ http://img706.imageshack.us/i/sales8910021.jpg/
[Repeater-Builder] Cable lengths
Here's an excerpt from a TX RX publication that ties in with this discussion Adverse cable length between Duplexer and transmitter using varactor or broadband hybrid combining type transmitter outputs. Even though the Duplexer VSWR is flat on frequency, the reflected impedance of the Duplexer off resonance, transformed by changing cable lengths, can cause parasitics to be generated. Change the length of cable between the transmitter and duplexer, traversing through a half wave in increments of between 1 and 2 inches until the desensitization ceases or is minimal. A ferrite isolator will also cure this condition when it is installed between the transmitter and duplexer. However, this is a much more expensive remedy. Chuck WB2EDV
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] HYT Repeater vs. Trbo Repeater
The HYT repeater is actually a Proper repeater and has been designed around the Spectra Engineering MX800 http://www.spectraeng.com.au/So if you are looking at implementing a DMR repeater into a RF dense site, I'd definitely know which way I'd go. No questions Gareth Bennett RadioSystems Limited P.O. Box 5202 Dunedin 9024 New Zealand DDI: (03) 489 1101 FAX: (03) 489 1151 MOB: (0224) 588 377 gare...@radsys.co.nz - Original Message - From: k2aau To: Repeater-Builder@yahoogroups.com Sent: Sunday, August 15, 2010 1:49 AM Subject: [Repeater-Builder] HYT Repeater vs. Trbo Repeater Has anyone done any comparison testing between the HYT Repeater and The Motorola Trbo repeater? I am particulary interested in making a future purchase of either one. I have read about the IPsec concerns and that to me is really not an issue. I am sure that HYT will address that concern as time goes forward. From what I have been told, the Trbo consists of 2 mobile radios used for receive and the other for transmit. Whereas, HYT is one radio with a Duplexed receiver and transmitter well isolated from each other. It is also my understanding that the company HYT's vendors are more user friendly in pricing and support compared to Motorola when it comes to accessories, firmware updates and programming. Thanks in advance for any information. Artie k2aau
Re: [Repeater-Builder] new member introduction
On Aug 12, 2010, at 9:09 PM, Zephyr wrote: Thanks for having me in your group. I am a long-time military veteran and a paramedic. I hope to learn a lot from the group. One of the reasons I joined the group is to find out what kind of EMP hardening is considered when designing and building repeaters? Very little, typically. Almost all have solid-state components that would be utterly dead after an EMP. Tube gear that survives EMP better is virtually all gone. And user radios are required for any repeater to be useful, and they'd all be totally dead too. So... the rest of your posting sure sounds like an advertisement for another list, which is generally bad Netiquette, unless the lists had something a little bit more in common. But I'll give you the benefit of the doubt since you used a real callsign and name on your signature line, even though your From is a pseudonym. Personally, I find pseudonym-bearers on the Internet usually need this advice: If you want to be somebody else, change you mind. Seriously. Or at least have the pseudonym match something you are, or something you do. Anyway, to finish answering the question: About the closest repeaters get to EMP Hardening outside of the military world (if even then...), is that a lot of repeaters in the West are in old ATT microwave facilities that were built as blast-hardened for specific distances and levels of nuclear bombs. The gear that used to live in them was hardened for various levels of EMP, but that gear is long-gone, removed from the buildings when ATT scrapped them and the military stopped paying. They have other communications systems and links today. The buildings will probably be standing for another 100 years. The towers are built hellaciously strong, too... but are showing signs of age. Even the outhouses were over-engineered, and I have an engineering drawing of an official ATT outhouse around here somewhere. Those were not blast-hardened nor EMP hardened, so apparently if you were unlucky enough to be caught at the site during a nuclear exchange, you might not have modern toilet facilities afterward. A small price to pay, I suppose. ;-) -- Nate Duehr n...@natetech.com
Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)
On Aug 14, 2010, at 12:57 PM, Scott Zimmerman wrote: I am subscribed to all of my groups in 'single e-mail' form. I have configured Thunderbird to sort those groups into individual folders. By doing this, I can look at things in a digest mode. If I want to get rid of a bunch at one clip, I can select all and hit delete. Just my 2c worth of ideas. Scott I agree with Scott, and take this one step further. I use an IMAP server (the real deal, not Microsoft's wacked-out IMAP in Exchange), and have the *server* sort all the mail into folders before it ever even gets looked at by my mail client software. Thunderbird, Apple's Mail.App on the Macs, the iPhone, the mail provider's mail web interface... all have the same view of the mail when I log on, and I can choose whether to read list mail (all nicely sorted and tagged as new mail in various folders) or just read the important stuff in my Inbox. The tools for managing e-mail are out there. They're just not commonly used. I'd go nuts if all this stuff came directly to my Inbox. That'd be crazy. List mail isn't personal mail, and the two don't need to ever mix. A challenge: For a highly technical hobby, very few hams have *really* done a deep-dive into their mail software and learned the feature-set. Give it a shot, it's well worth it! :-) You might be able to reward yourself with a nice Repeater-Builder folder, where all the RB mail goes, all by itself... and you can then read (or delete large swaths by subject line, even... since that's what the Subject line was created for, after all...) at your leisure! Have fun with it, -- Nate Duehr n...@natetech.com
Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)
I'm the opposite. I want all my email dumped in one inbox. I'm afraid if it gets sorted to different folders, something's bound to get missed. Just like the mailman puts all my snail mail in one mailbox. Works just fine. Same reason I prefer list servers to forums - I don't want to have to go and look somewhere. Chuck WB2EDV - Original Message - From: Nate Duehr n...@natetech.com To: Repeater-Builder@yahoogroups.com Sent: Saturday, August 14, 2010 8:41 PM Subject: Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn) On Aug 14, 2010, at 12:57 PM, Scott Zimmerman wrote: I am subscribed to all of my groups in 'single e-mail' form. I have configured Thunderbird to sort those groups into individual folders. By doing this, I can look at things in a digest mode. If I want to get rid of a bunch at one clip, I can select all and hit delete. Just my 2c worth of ideas. Scott I agree with Scott, and take this one step further. I use an IMAP server (the real deal, not Microsoft's wacked-out IMAP in Exchange), and have the *server* sort all the mail into folders before it ever even gets looked at by my mail client software.
RE: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)
And I am one of those with separate folders for two reasons, first it makes things easier to see, and I have never had a problem with getting email mixed up, I subscribe to multiple yahoo groups and each one has its own folder which makes it easy to see when there is new email from each group. Secondly and most important to me I get so much business related email on my Blackberry that by using folders I don't get groups to my BB, and so I can concentrate on business emails and when I check in with my desktop or laptop I can see the groups with messages since the last time I have looked at them. In this case, then, a few spam messages are just easy to delete. I know from experience that spammers don't have to have access to your email account to spoof your email address, since mine has been spoofed multiple time. Andy W6AMS From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Saturday, August 14, 2010 6:01 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn) I'm the opposite. I want all my email dumped in one inbox. I'm afraid if it gets sorted to different folders, something's bound to get missed. Just like the mailman puts all my snail mail in one mailbox. Works just fine. Same reason I prefer list servers to forums - I don't want to have to go and look somewhere. Chuck WB2EDV - Original Message - From: Nate Duehr n...@natetech.com mailto:nate%40natetech.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Saturday, August 14, 2010 8:41 PM Subject: Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn) On Aug 14, 2010, at 12:57 PM, Scott Zimmerman wrote: I am subscribed to all of my groups in 'single e-mail' form. I have configured Thunderbird to sort those groups into individual folders. By doing this, I can look at things in a digest mode. If I want to get rid of a bunch at one clip, I can select all and hit delete. Just my 2c worth of ideas. Scott I agree with Scott, and take this one step further. I use an IMAP server (the real deal, not Microsoft's wacked-out IMAP in Exchange), and have the *server* sort all the mail into folders before it ever even gets looked at by my mail client software.
Re: [Repeater-Builder] Repeater Stuff For Sale!
what is the input power on the 200 watt Vocom amp? K+John - Original Message - From: n2len To: Repeater-Builder@yahoogroups.com Sent: Saturday, August 14, 2010 9:24 PM Subject: [Repeater-Builder] Repeater Stuff For Sale! Motorola RKR-1225 VHF Repeater with Rack Mount Currently programmed for Hamsplit $475 Shipped and Insured Motorola R-1225 UHF Repeater Just Radio and Control Head Unit Hamsplit down to 444MHZ $425 Shipped and Insured Cat 400 Linking Controller and RME-200L Rack Mount with Ed-400W Windows Programming Software $325 Shipped and Insured Cat RLS-1000B Remote Link Switch Board with RME-200L Rack Mount Enclosure. $125.00 Shipped Pacific Research RI-310 Repeater Controller Ror the VXR-5000 Repeater Direct Replacement for the stock Internal Controller Plug Play $400.00 Shipped TPL RXR Series VHF 150 Watt Repeater Amplifier Rack Mount/Fan $375.00 Shipped TPL RXR Series UHF 100 Watt Repeater Amplifier Rack Mount/Fan $350.00 Shipped Two Vocom UHF Repeater Amplifiers Working Condition of both Unknown 100 Watt Factory 462.925 UVC100-10RF $125 Shipped Vocom UHF Repeater Amplifier Working Condition Unknown 200 Watt Factory 462.925 UVC200-80RFF Rack Mount/Fan PAYMENT PAYPAL! E-mail too: n2...@aol.com
Re: [Repeater-Builder] Coax length, etc.
Russ Hines wrote: 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. I largely disagree. Most modern duplexer designs (within the last 25 years or so) use compensating elements to make the duplexer or cavity temperature stable. Invar is a nickel-steel alloy that exhibits about 1/10 the thermal expansion as a common carbon steel counterpart. Invar is used to make the tuning rod - many times it's threaded. The rest of the duplexer or cavity is usually made of similar metals and generally thermal expansion occurs across these components equally, resulting in extremely low frequency drift over its rated operating temperature. 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. What? Maybe you would like to have another chance at that one Kevin Custer
Re: [Repeater-Builder] Re: Coax length, etc.
Sid, I think I found your formula. Look on page 62 of: http://www.repeater-builder.com/antenna/pdf/ve2azx-duplexerinfo.pdf BTW, my guess was wrong. Length is expressed in inches. 73, Russ WB8ZCC On 8/13/2010 1:44 PM, Russ Hines wrote: Hmm, the formula is a bit off, but... 30 x 32.785 = 983.55. I'll also bet length is expressed in feet. Looks eerily like someone wants you to cut a one-wavelength piece of coax cut at the mean repeater frequency. Just a guess. 73, Russ WB8ZCC On 8/13/2010 11:38 AM, Sid wrote: 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] Coax length, etc.
Ross Johnson wrote: So will someone post a simple rule of thumb... If you have the option of optimizing cable length from PA to first cavity, IE you haven't made them yet what's the best simple rule of thumb to follow to build them to avoid reactance. 1/2wl if allowed minus coupling loop depth? Or is that past a simple thumb. Simple rule - there is none. The length can be determined experimentally as outlined in several publications of various duplexer manufacturers. I use the length I need to do a good job - then, if the transmitter is unhappy, I build a cable long enough to do the job and satisfy the transmitter. Kevin
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. 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. 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? For one thing the reactance causes them to draw more current than normal. Again, why? 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 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. 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. 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. 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 the cable at least that length. The cable length between multiple cavities is predictable. As an example between two notch cavities; the first notch presents a very low impedance. With a quarter wave line to the next cavity that low impedance is transformed to a high impedance at the input to the next cavity. That high impedance is then presented with a very low impedance of the second cavity. This critical length cable increases the ultimate notch depth because the high impedance that the cable presents and the low impedance of the cavity form a voltage divider. The greater the ratio the better the rejection. 'zactly. When done right, you can pick up close to 6 dB additional net notch depth when cascading notch (or pass/notch) cavities when the intra-cavity cables are cut this way. Jeff WN3A
RE: [Repeater-Builder] Coax length, etc.
So will someone post a simple rule of thumb. If you have the option of optimizing cable length from PA to first cavity, IE you haven't made them yet what's the best simple rule of thumb to follow to build them to avoid reactance. 1/2wl if allowed minus coupling loop depth? Or is that past a simple thumb. Also, This will obviously not work well for 220 or 440 or a most vhf repeater setups. So what would the next ideal cable wl be? And so forth. The reason I ask, if your building new cables why not? Answers on here seem to range a lot. There is no simple rule of thumb, and if anybody tells you that there is, ask them how do you account for the unknown-length of coax that's *inside* your transmitter/amplifier before it gets to the antenna jack. --- Jeff WN3A
RE: [Repeater-Builder] Coax length, etc.
OK, I think, for the most part, we're on the same page. I'm cuttin' and trimmin' a lot here... And this is where I believe the duplexer manufacturers are covering their butt. They don't want the problem with complex reactance presented by the duplexer to be their problem. Not that I don't agree, because it's usually the transmitter that is really at fault. I think that last sentence speaks volumes on the matter. Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II repeater and gets 50 watts out the antenna port. He does his homework and realizes that he should only be loosing 29% with the 1.5 dB of insertion loss stated in the paperwork - but he's loosing over 50%. Ah, but is he really *losing* 50 percent in the duplexer, or is transmitter not making the full 110 watts output to start with? Maybe his transmitter is really only delivering 70 watts to the duplexer. Is it an issue of the duplexer's loss being high, or is the problem the transmitter's not making power? Seems to me it's really the latter. The duplexer manufacturer supposedly engineered and tuned it for a 50 Ohm system. Well, kinda. Many duplexers are spec'ed for 1.5:1 (14 dB RL) input VSWR max. Fortunately, I rarely see any that are that bad. I'll gladly trade off a tenth of a dB of insertion loss for several (if not 10 or more) dB of return loss improvement when I'm tuning on the VNA, but some hams are greedy and don't think along those lines when they're tuning... He knows that the cable he connected to the transmitter is good, because when he disconnects the end going to the transmitter port of the duplexer and connects it to his Bird 43 terminated with a good load - it reads 110 watts. Yes, but did he have a second Bird between the Tx and the duplexer when he was measuring power output? That would have told the real story. Now, is the transmitter becoming spurious Now all bets are off. and the cable length being changed in length satisfies the match between the duplexer and transmitter - I don't know... All I can tell you is I have followed the suggestions written in the WACOM manual and it has worked. I had one instance of a ham radio club loosing PA's left and right on their 2M machine. They told me of the situation and I offered to do a little testing. The 110 watt PA would put out 110 watts into a Bird and dummy, but only 45 watts was coming out the antenna port of the duplexer. At the time I didn't own a spectrum analyzer. The repeater wouldn't duplex without desense. I changed the length of the line between the PA and duplexer until I got the power to read about 75 Watts as I remember. That was 13 years and they still have the same PA - no desense either. Out of morbid curiosity, what kind of PA was it? You are changing the VSWR when tuning the cavity closest to the transmitter. Yes, but once you've adjusted that cavity, from that point on, changing the cable length doesn't vary the VSWR. That was my point - changing the cable length doesn't change VSWR. I realize that impedance transformation cannot occur when you have a 50 Ohm cable (of any length) and a perfect 50 Ohm load - but I think you will agree that a duplexer doesn't, in any way shape or form, present a nice 50 Ohm load. Well, it can get pretty damn close. I can send you some VNA plots of duplexers with input Z's well in excess of 30 dB return loss, some approaching the limits of my test equipment. Of course, when hooked up to an antenna instead of being terminated in a precision load, all bets are off, but hey, that's not the fault of the duplexer... Some transmitters just cannot deal with it without some form of matching after the fact - like a Z-Matcher, Isolator, Circulator, or even a critical cable length. I don't like those transmitters :-) GE MASTR II 110 watt 150.8 to 174 MHz PA and WACOM WP-641. Thinking...thinking...no, haven't done that one. Motorola MICOR 150.8 to 162 MHz PA and WACOM WP-641. Yes, have done that combo, several times that I can think of. Actually, one of the repeaters was low-split from the factory (out of Canada) now that I think about it, so that doesn't count, the others were all H split with no PA mods. Didn't do anything special with cable lengths. Hamtronics 45 Watt 2M PA and Sinclair Q-202. Haven't done any Hamtronics. Well, I cannot believe that I'm the only person on this list that has had success with optimizing the length of cable between the duplexer and transmitter/PA. I don't doubt that others have seen positive (or negative) effects from varying cable lengths - I just said I've never had to resort to doing it, using the equipment that I've used, with the equipment tuned the way I've tuned it. I'll get us some tickets for Vegas - Jeff. I think ZZU has the right idea. He's down in MX-land right now, probably sitting on a beach laughing at us working
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
