Re: Topband: Compromise vertical loading questions
Hi, Bjorn Well I would expect that moving the loading coil higher would be more beneficial than improving the top loading spokes, as it would move the high current portion of the antenna higher aboveground (the radial) and there would, hopefully, be less loss In the loading coil by having it in a lower current region of the antenna. Improving the top loading spokes might be helpful also, but I think less than moving the loading inductance higher. Of course, since the loading inductance will be in a lower current region of the antenna, it may require a bit more inductance to resonate the antenna. Good luck! Have fun! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Björn SM0MDG Sent: Wednesday, January 29, 2014 2:48 AM To: topband@contesting.com List Subject: Topband: Compromise vertical loading questions Here are some question for anyone with more tech skills than me; My compromise vertical at 8Q7BM is made of thin wire attached to a DX-Wire 15 meter glass fibre pole. The vertical wire goes all the way up, but as the poles top sections are very thin/weak the three top loading spokes (each 12 meter long) are attached at about 13 meter. The antenna has a 1/4 elevate radial towards the water at 2-3 meter height. The whole structure is within 1/4 wave of the water line. The antenna is self resonant at 2.2 MHz and I use a coil wound on a water bottle to bring it down to 1.8. The coil appears to be about 8-10 uH according to online calculators. My questions are; How much I can improve by moving the coil up. What improvement should I expect if center loading at about 7 meter? How about moving the coil all the way up to the top loading spokes? Is it worth the effort? (the pole wont support much up there). My top loading spokes are sloping more than the recommended angle. According to the ON4UN Low Band book I got the impression that the difference should be minimal when close to salt water. I have tried to slope them less, but easily get in trouble with the weak pole in the wind. And there are pats to the beach every where so options are few. Which one of the two above actions would be the most beneficial? Move the loading coil higher up or rearrange the top loading spokes for a better angle? 73 de Björn, SM0MDG 8Q7BM SE0X _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Compromise vertical loading questions
How much I can improve by moving the coil up. What improvement should I expect if center loading at about 7 meter? How about moving the coil all the way up to the top loading spokes? Is it worth the effort? (the pole won’t support much up there). The coil does not do much at all to current distribution. The spokes pretty much set the current distribution in the antenna, so moving the coil would have almost no effect. My top loading spokes are sloping more than the recommended angle. According to the ON4UN Low Band book I got the impression that the difference should be minimal when close to salt water. I have tried to slope them less, but easily get in trouble with the weak pole in the wind. And there are pats to the beach every where so options are few. The slope of the spokes has virtually the same effect on current distribution over earth as over sea water. The downward slope, in effect, shortens the vertical. This is because when folded down the current into the spokes opposes current in the vertical, subtracting from effective height. The cancelation is a cos function as well as ampere-feet (or ampere-meters), so it rapidly becomes worse at smaller angles. It actually deals with EM field intensity and direction as the fields from the wires and radiator interect at differing angles. Which one of the two above actions would be the most beneficial? Move the loading coil higher up or rearrange the top loading spokes for a better angle? The coil would have almost no effect. The loading wires effect would depend on angle. 73 Tom 73 de Björn, SM0MDG 8Q7BM SE0X _ Topband Reflector Archives - http://www.contesting.com/_topband - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4259 / Virus Database: 3681/7041 - Release Date: 01/28/14 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
2.) #10, ignoring connection imperfections, has about .01 ohms per 10 ft. That's up to 0.2volts with 20 amps of power supply loop current. Not a problem unless you have bonded DC- to the power supply chassis. Bingo. Virtually EVERY piece of gear has a bonded negative to chassis. The whole concept is screwed up, especially negative lead fuses, but it is what it is. No one can force the industry to float negative grounds from chassis. Even RF transistors have the metal bases tied to emitters, which forces a negative ground to heatsinks unless the designer can seriously compromise cooling. Also, almost every Ham radio manufacturer in the world isolates the low level audio shields inside radios except at one point because they are well aware of issues with the large currents in 12V solid state high power systems. Yep. It's called The Pin One Problem, and is a well documented cause of hum, buzz, and RFI. ...and no matter how much we idealize the situation in our minds, we cannot change the population and things we cannot change just because we dislike a $2 transformer for some reason. Ham stations have grounds, and those grounds cannot be bonded perfectly to the mains, nor will many people bond them at all. WRONG! We MUST bond all grounds in a facility for lightning safety, and for safety of personnel. And when done completely and properly, it SOLVES problems. We cannot force the world to do things that are difficult, expensive, and/or inconvenient. Because of that, we have to move away from the theoretically ideal world of zero ground potential difference and face the way the world really works. Very few people are going to bond grounds properly, and fewer still will drill into a computer or other equipment to add a ground lugs or modify equipment to float negative returns from chassis. The only thing eliminating the isolation transformer does, other than saving $2, is ruin systems in the real world. It is a terrible suggestion. No accessory manufacturer will ever follow your directive. As an example, when MFJ designed the voice keyer they cheaped out or neglected the isolation transformer. About 80%-90% of the units came back from audio distortion and RF problems. They came to me, and I redid the layout with a simple $1.10 audio transformer and low frequency floating shield system. Complaints vanished. Now I could have written a letter like this: Dear Customer, Because we have some opposition to using $1.10 isolation transformers, we would like you to rewire your station. Please do the following: 1.) Never ground the case of the VK to anything except a perfect station ground buss that is not common with the main supply 2.) Never power the VK from the station supply. Always use a DC filtered ground independent wall wart 3.) Never allow the case to contact any other metal or conductors in the shack 4.) MFJ is not liable for any damage to the radio mic input circuit by accidental grounding of the + power supply lead Sincerely, MFJ but silly me, I went ahead and added the transformer so they could pretty much connect it any way they like without blowing up their radio or having distortion. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Compromise vertical loading questions
Hi, Bjorn Well, I can't argue with JC. With my first ever inverted L for 160, I had similar experiences as did his friend, AA7JV with; submerged radials. In my case, the inverted L was on the dam of a lake behind my house. Not salt water, of course, but the lake had been treated with some amount of copper sulfate to control vegetation growth. I cut perhaps 8 1/4 wave radials of bare 14 gauge stranded wire and weighted the ends with bricks. I then used my canoe to fan the radials over nearly 180 degrees of semi -circle and submerged them in the lake. Like AA7JV, I could see the driving point impedance drop and the VSWR bandwidth of the antenna system decrease as I added radials, reducing the ground losses. One of my earlier QSOs wasn with Jacky, 3B8CF, on Mauritius around my sunset, but I also worked VK3, VK6, JA etc. - all with about 400W. So, if you could move that antenna nearer the water's edge, and submerge that radial in salt water, I expect you might see some improvement. In any case, GL and have fun!! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of JC N4IS Sent: Wednesday, January 29, 2014 8:39 AM To: 'Björn SM0MDG'; topband@contesting.com Subject: Re: Topband: Compromise vertical loading questions Hi Bjorn How much I can improve by moving the coil up. What improvement should I expect if center loading at about 7 meter? How about moving the coil all the way up to the top loading spokes? Is it worth the effort? (the pole wont support much up there). . Not much, changing the loading would increase the signal 5-10% , it is around 1 db, however if you can get close to salt water and get the radials wet your signal can increase 10db or more. AA7JV can comment better on that, but close to the water is not good, in the water is unbelievable better. George used get several wires tied with a stone and through it into the water, as you increase the number of the wires, you can see the impedance changing. You will may lose some of the radials and they need to be replaced. The radials could be very short and thin but they will work if in the water. I can hear you almost every day with the antenna you are using now. Regards JC N4IS _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: FT5ZM
Good morning all. It appears I was duped two days ago. The apparently real FT5ZM just showed up 48.5 hours later, but too late for me. The sun was already 10 minutes in the sky when the very weak signal was heard at this QTH. The NA west coast is calling right now but I have not heard any of them make a contact. I apologize for the misleading info of two days ago. The comment by LY5W on the FT5ZM web site re working Amsterdam on 160 M has now been removed. However, here is the copy and paste that I did of that comment. I sent this to Juhani Viitala, OH3SR,at his request. Saulius Zalnerauskas · Works at Laisvo Oro Direktorius TNX for 160m QSO - EASY! Great ears! LY5W - First Call Reply · 4 · Like · Follow Post · 5 hours ago Branislav Hačko · Centar za socijalnu medicinu at Zavod za javno zdravlje Kikinda Congrats! YU7U Reply · Like · 47 minutes ago This is from http://www.amsterdamdx.org/an-avalanche-of-emails/ Good luck to everyone. de Milt, N5IA -Original Message- From: K4SAV Sent: Monday, January 27, 2014 7:50 PM To: topband@contesting.com Subject: Re: Topband: FT5ZM Merv if you look at a gray line map you will see that the path from New Mexico to FT5ZM at 1350Z is in the gray line while at the same time its three hours after your sunrise. Also after sunrise for most of eastern US. Jerry, K4SAV On 1/27/2014 9:50 AM, Merv Schweigert wrote: Now thats a strange one Milt, I was up and ears peeled at 1330Z until now 1545Z and never heard a peep outta him, never heard anyone calling at all, what Freq was this happening on? Only stations on 160 were NH0Z and V63DX, couple JAs How in the world did we all miss him? Curious to freq you heard him on? I also dont see any reverse beacon hits for him.. Color me dumb, 73 Merv K9FD/KH6 He was first discernable here at 1350. In the log at 1400. It is now 1422 and he is fading with my sunrise. The signals peaked at S3 on the Beverages for about 20 minutes, but was good copy on ALL 16 Beverages. This indicates a VERY HIGH arrival angle here near the Amsterdam antipode. He was good copy (S1) on a full wavelength horizontal loop just 10 feet AGL. He is now working northern Scandinavian station as well as NA west coast as he fades away. Still 449 at 1427. 73, and good luck to all. de Milt, N5IA - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4259 / Virus Database: 3681/7035 - Release Date: 01/26/14 _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4259 / Virus Database: 3681/7038 - Release Date: 01/27/14 - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4259 / Virus Database: 3681/7041 - Release Date: 01/28/14 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
That's not entirely correct... Triplen harmonics are created by non-linear loads, but the voltage developed on the neutral as a result of them is a result of voltage drop between the source of the problem and the return which will be one or more utility transformers. The farther you are from the transformer the worse the issue will be (higher voltage developed). Triplen harmonics primarily result in additional heating in the neutral and transformer due to higher than normal currents (since they don't cancel). Triplen harmonics are also becoming less of an issue as many electronic loads now incorporate power factor correction. This used to be a very big deal in datacenters due to older computer power supplies (which are rectifier loads and very non-linear), but most new equipment isn't a problem. Note that high leg delta, when used to deliver 120/240 single phase power will *always* have the center tap grounded and that includes in industrial, 3-phase customer sites. If the center tap isn't grounded then you would have to have a corner-grounded system, but there is always, by code, a ground bond at the site. The only impedance-grounded system I'm aware of is the old 4800 volt primary system but in that case all of the step-down transformers on the poles also provide transformer isolation between the primary and secondary (since it's not possible to use autotransformers in that application). Most of the newer (since the 70s) power distribution used by utilities is a wye on the primary, and the neutral of that wye is grounded at each pole and the substation. All customer (both single a three phase) services have their ground/neutral bonded to that common ground/neutral used by the primary. And note that from the utility's perspective, on the poles, the neutral and ground are essentially the same thing (at least in terms of the way the system is wired). And our home and ham station grounds, when properly bonded to the service entrance, WILL share current with the utility system. I see about 7 amps at home that comes from the utility (but I have a ground ring, lots of rods, probably 500+ feet of copper in the ground and a well casing). It's not a problem, but it's there. -Bill The voltage driving that current isn't high, it is caused by the neutral voltage drop back to the substation, but it is a real voltage and current that exists. No, it is caused by triplen harmonics combining on the neutral (and ground) of 3-phase systems to add rather than cancel. That's the source of power line buzz -- 180, 360, 540, 720 Hz. While we don't have 3-phase power in our homes, the power on the street is nearly always 3-phase, and often a very nasty variation of 3-phase called high leg delta. It's 240V delta, with all three phases fed to light industrial customers, and one of the legs center-tapped to feed single-phase users. Those 3-phase users get no neutral and no ground, so their harmonic current finds its path to ground through OUR neutral. THAT'S the source of our buzz. And yes, it's not unusual to see an amp or more of that stuff on our neutral. High leg delta is all over mixed residential/light business/industrial neighborhoods of nearly all cities, and it's what I've got in the Santa Cruz Mountains. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Compromise vertical loading questions
One additional point about this that I might not have expressed in enough detail. When a top hat with significant capacitance compared to distributed capaciatnce along the radiator is involved, current tends to become very linear throughout the radiator no matter where any loading inductance is inserted. Bjorn has a particularly extreme example for this, because the SRF of the vertical without any inductor was 2.2 MHz. The antenna is self resonant at 2.2 MHz and I use a coil wound on a water bottle to bring it down to 1.8. The coil appears to be about 8-10 uH according to online calculators. He only has 100 ohms of reactance-cancelling inductance, which further proves his statement that the antenna SRF is 2.2 MHz. While the amount of reactance has no direct bearing on distribution, the fact it is so low means current is pretty much all flowing into the hat wires. Series reactances do not change distribution above the reactance because it is a series system. Shunting capacitances or reactances do. The only way current can change is through an electric field and displacement currents. The significant capacitance, in his case, is the hat. The only two places where significant changes are possible without a significant height increase are: 1.) reducing foldback of the hat 2.) improving the ground system 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
And our home and ham station grounds, when properly bonded to the service entrance, WILL share current with the utility system. I see about 7 amps at home that comes from the utility (but I have a ground ring, lots of rods, probably 500+ feet of copper in the ground and a well casing). It's not a problem, but it's there. -Bill Absolutely, on all points including harmonics and noise, Bill. The reason my power line neutral to ground system current is so exceptionally low is the location of the substation and the very light load on my lines. I'm in a rural area and the primary line is lightly loaded. It also runs almost directly towards the sub-station, with other branch lines, and becomes three-phase a few miles away. If I have significant current (voltage is never that high) between my ground systems and the mains in an almost ideal case, most people would have a much worse situation. Advising people to not isolate grounds on audio lines between different cabinet grounded pieces of gear is a reversal of progress made with interfaces. It really can only bring problems to all of us in the long term. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
On 1/29/2014 5:15 AM, Tom W8JI wrote: 2.) #10, ignoring connection imperfections, has about .01 ohms per 10 ft. That's up to 0.2volts with 20 amps of power supply loop current. Not a problem unless you have bonded DC- to the power supply chassis. Bingo. Virtually EVERY piece of gear has a bonded negative to chassis. The whole concept is screwed up, especially negative lead fuses, but it is what it is. No one can force the industry to float negative grounds from chassis. Even RF transistors have the metal bases tied to emitters, which forces a negative ground to heatsinks unless the designer can seriously compromise cooling. There is no problem with V- bonded at load equipment (the rig). The problem is bonding at the power supply, and that is EASY to fix -- indeed, many (most?) power supplies are built either with V- NOT bonded, or with nothing chassis-referenced and a removable jumper at the output. All Astron supplied I've looked at are built this way -- indeed, all I've looked at had the bond to the mounting stud of terminal strip that was insulated from the chassis by paint. So they were NOT bonded, and neither was the green wire, which went to the same lug. Also, almost every Ham radio manufacturer in the world isolates the low level audio shields inside radios except at one point because they are well aware of issues with the large currents in 12V solid state high power systems. Yep. It's called The Pin One Problem, and is a well documented cause of hum, buzz, and RFI. ...and no matter how much we idealize the situation in our minds, we cannot change the population and things we cannot change just because we dislike a $2 transformer for some reason. Indeed we can -- the pro audio world changed over a period of ten years or so. Sadly, the consumer world never got the word, and hams, with their superior I grew up in broadcast and know the way its done attitudes haven't bothered to learn anything new in 40 years. We cannot force the world to do things that are difficult, expensive, and/or inconvenient. Huh? Ground bonding is required by LAW in most of the civilized world, and part of the National Electric Code that has been adopted as an electrical Building Code almost everywhere in the US. And in those places where NEC has not been adopted directly it is the model for local codes (LA, Chicago, for example). Beyond that, it is good engineering practice. Because of that, we have to move away from the theoretically ideal world of zero ground potential difference and face the way the world really works. Who's talking about theoretical? I'm certainly not. The bonding methods for a ham station that I have outlined work for ham stations because they are good enough -- they provide a transmitted signal to noise ratio of 50 dB, not good enough for broadcast, but plenty good for us. Indeed, I view the knee-jerk use of broadcast techniques, including transformers where they are not needed, as purist. Very few people are going to bond grounds properly, and fewer still will drill into a computer or other equipment to add a ground lugs It's trivially easy for most equipment -- DB connectors are bonded to the chassis of laptops, the chassis of most computers have exposed screws, all ham gear has a chassis lug. or modify equipment to float negative returns from chassis. No need to do that except at the power supply, The only thing eliminating the isolation transformer does, other than saving $2, is ruin systems in the real world. It is a terrible suggestion. No accessory manufacturer will ever follow your directive. Bonding cable shields to the chassis has been an AES Standard for nearly ten years, and it's been widely implemented in pro audio since the late '90s. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
K9YC writes: There is no problem with V- bonded at load equipment (the rig). The problem is bonding at the power supply, and that is EASY to fix -- indeed, many (most?) power supplies are built either with V- NOT bonded, or with nothing chassis-referenced and a removable jumper at the output. All Astron supplied I've looked at are built this way -- indeed, all I've looked at had the bond to the mounting stud of terminal strip that was insulated from the chassis by paint. So they were NOT bonded, and neither was the green wire, which went to the same lug. My observations of Astron ground wiring are similar to yours but I come to a different conclusion. The V- goes to the terminal strip lug and the terminal strip lug is attached to painted chassis by screw, but I would assume that this makes a poor and intermittent connection between V- and chassis ground. Insulated by paint seems like a very poor idea. It's like someone thought my boss told me to do this, I don't think I it should be done, and if it isn't worth doing then it isn't worth doing well :-) Lifting the ground connection to V- is a very common modification to Astrons and some sources (e.g. http://www.repeater-builder.com/astron/astron-intro-stuff.html ) tell me that Astron has vacillated between grounding V- to cabinet and not grounding and isolating it with 3K ohm resistor over the years. Tim N3QE _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
On 1/29/2014 9:12 AM, Shoppa, Tim wrote: Insulated by paint seems like a very poor idea. It's like someone thought my boss told me to do this, I don't think I it should be done, and if it isn't worth doing then it isn't worth doing well:-) Oh -- I'm certainly not recommending it, nor am I suggesting they did it intentionally. Rather, I'm observing that it's a common manufacturing defect, and certainly not limited to Astron. I've seen it in products from many manufacturers, including older Elecraft products (the band decoders), but they've long since gotten religion and fixed that issue. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
I bought my Astron SS-30M in 2000 and shortly after found the V- tied to chassis, which I removed. 73, Gerry, K8GT On 1/29/2014 12:12 PM, Shoppa, Tim wrote: snip Lifting the ground connection to V- is a very common modification to Astrons and some sources (e.g. http://www.repeater-builder.com/astron/astron-intro-stuff.html ) tell me that Astron has vacillated between grounding V- to cabinet and not grounding and isolating it with 3K ohm resistor over the years. Tim N3QE _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
Jim, Asking customers to modify equipment, which might also include adding ground studs to computers, is just silly when the entire issue is solved with audio line isolation in the interface line. There is no problem with V- bonded at load equipment (the rig). The problem is bonding at the power supply, and that is EASY to fix -- indeed, many (most?) power supplies are built either with V- NOT bonded, or with nothing chassis-referenced and a removable jumper at the output. All Astron supplied I've looked at are built this way -- indeed, all I've looked at had the bond to the mounting stud of terminal strip that was insulated from the chassis by paint. So they were NOT bonded, and neither was the green wire, which went to the same lug. We cannot force the world to do things that are difficult, expensive, and/or inconvenient. Huh? Ground bonding is required by LAW in most of the civilized world, and part of the National Electric Code that has been adopted as an electrical Building Code almost everywhere in the US. And in those places where NEC has not been adopted directly it is the model for local codes (LA, Chicago, for example). Beyond that, it is good engineering practice. At risk of being repetitious, neither a manufacturer nor an author can force customers to do things that are inconvenient, expensive, time consuming, not commonly done, or difficult, just to save a $2 transformer. The manufacturer, or the person giving advice, would have to be willing to take the heat for saving the $2 when the savings makes the entire system more critical, difficult, complicated to implement, and/or risky to equipment or performance. There is no advantage to eliminating the transformer, other than cost (and some people in the audio-fi world don't like transformers). There is considerable worry and risk. It is actually pretty silly to not isolate the line, unless it is all mounted in one metal cabinet rack! I can 100% assure everyone that no manufacturer in their right mind would put an interface product out with common-connected unbalanced lines. If we think about it, we even isolate unbalanced Beverage antennas from unbalanced coaxial lines! This is how good system planning works in the real, imperfect, world we live in. We might want, dream of, or demand, a perfect world with everyone and everything all lined up the way we want, but it virtually never happens. Good engineering plans around the imperfections. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
Triplen harmonics, in most facilities, are caused primarily by lighting ballasts and electronic (rectifier-input) power supplies. The newer switching power supplies have a power factor controller in the first stage that acts something like a current regulator preceding the actual switching power supply. You can look up data sheets for these devices. The result is a .95 or better power factor in most cases, and almost no generation of triplen harmonics on the neutral. My understanding is that the EU requires power factor correction in computer power supplies and since the manufacturers want to have one power supply to use globally (100 - 250 volts, 50/60 Hz, we've all seen this :-), they just build to the most stringent standard and keep their volume costs down with the single part. The result of the corrected power supplies in datacenters is that we don't need to use K-rated transformers (rated for high harmonic content) anymore which saves a *lot* of money. I have found almost all of the commercial equipment (network gear, routers, rack-mount servers) incorporate PFC. Many, but not yet all, of the desktop computer power supplies are also going this route. Newer electronic ballasts are also incorporating PFC. It's all part of an effort to keep electrical costs down. It makes a difference in large facilities, especially when you consider the long lifetime of most of the commercial equipment involved. -Bill Triplen harmonics are also becoming less of an issue as many electronic loads now incorporate power factor correction. Interesting. Virtually all electronic equipment are non-linear loads -- they are the power supplies in that equipment, which virtually all include a rectifier and capacitor-input filter. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Compromise vertical loading questions
On Wed, Jan 29, 2014 at 07:54 AM, Tom W8JI wrote: How much I can improve by moving the coil up. What improvement should I expect if center loading at about 7 meter? How about moving the coil all the way up to the top loading spokes? Is it worth the effort? (the pole won’t support much up there). The coil does not do much at all to current distribution. The spokes pretty much set the current distribution in the antenna, so moving the coil would have almost no effect. 73 Tom Here we go again, Tom spreading misinformation. IT IS important where the coil is placed in the loaded antenna. See the discussion at http://www.k3bu.us/loadingcoils.htm Also, QEX finally started publishing Barry's, W9UCW articles in QEX Jan/Feb 2014 issue describing actual measurements and results of their experiments. Interesting, that Tom admits that there is cos (diminishing) distribution of current along the straight wire - radiator, but when you roll that wire into a coil - magic - current becomes constant across the coiled wire according to Tom. The suggestion about loading coil placement to improve efficiency of (resonant 1/4 wave) antenna (trying to maintain maximum length of radiator with highest current) is to place the coil furthest away from the feed point. The further we go, impedance along the wire increases and number of required turns increase in order to maintain resonance for the length of wire, while having high current portion of the radiator the longest - stronger radiated field. My most effective mobile 160m antenna was fender mounted Hustler mast with loading coil on the top and loading wire going to the short mast on the front bumper of 1972 Buick LeSabre. Yuri, K3BU.us www.MVmanor.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Compromise vertical loading questions
The discussion is about the placement of an additional loading coil and its influence while the radiator is already loaded by a capacitance hat. So who spreads misinformation? -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Yuri Blanarovich Here we go again, Tom spreading misinformation. IT IS important where the coil is placed in the loaded antenna. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Chassis Bonding
Thanks for the update from someone still working in that part of industry. Yes, PF correction was mandated in EU something like 10 years ago. It's good news if this ripples back to our continent, even if our electrical codes haven't addressed this issue. . That said, as long as rectifier-capacitor input power supplies dominate the landscape, we'll have those harmonics to deal with. BTW -- for those following the discussion, the harmonics are generated because current flows in pulses at the positive and negative peaks of the AC waveform to recharge the input filter capacitor. A switching power supply simply takes the resulting DC, generates square waves at a higher frequency (typically in the 10-20 kHz range) that's easier to filter. The harmonic problem is NOT limited to lighting ballasts, data centers, etc. Nearly 20 years ago, a major Chicago broadcaster, WFLD-TV, had a very serious encounter with the high neutral currents that these harmonics can produce (nearly double the current in one phase of a well balanced system) and hosted a meeting of our local SBE chapter to talk about it. Their neutral hardware got so hot that they nearly had to shut down and go off the air. 73, Jim K9YC On 1/29/2014 12:52 PM, Bill Wichers wrote: Triplen harmonics, in most facilities, are caused primarily by lighting ballasts and electronic (rectifier-input) power supplies. The newer switching power supplies have a power factor controller in the first stage that acts something like a current regulator preceding the actual switching power supply. You can look up data sheets for these devices. The result is a .95 or better power factor in most cases, and almost no generation of triplen harmonics on the neutral. My understanding is that the EU requires power factor correction in computer power supplies and since the manufacturers want to have one power supply to use globally (100 - 250 volts, 50/60 Hz, we've all seen this:-), they just build to the most stringent standard and keep their volume costs down with the single part. The result of the corrected power supplies in datacenters is that we don't need to use K-rated transformers (rated for high harmonic content) anymore which saves a*lot* of money. I have found almost all of the commercial equipment (network gear, routers, rack-mount servers) incorporate PFC. Many, but not yet all, of the desktop computer power supplies are also going this route. Newer electronic ballasts are also incorporating PFC. It's all part of an effort to keep electrical costs down. It makes a difference in large facilities, especially when you consider the long lifetime of most of the commercial equipment involved. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Submerging variable caps in oil as substitute for vacuum variables
The author points out (correctly) the tempco issues with oil dielectric. Still I am intrigued by the thought of a remote tuning capacitor via hydraulic tubing :-). The capacitor plates could be as simple as two concentric cylinder conductors with appropriate spacers. I betcha crud collecting on the top of the oil would set voltage limit. Tim N3QE - Original Message - From: Pete Smith N4ZR [mailto:n...@contesting.com] Sent: Wednesday, January 29, 2014 05:42 PM To: topband@contesting.com topband@contesting.com Subject: Topband: Submerging variable caps in oil as substitute for vacuum variables The omega match for my shunt fed tower uses two 300 uF roughly 3000-volt variables I bought from Henry radio a few years ago. I think occasionally about running more than 100 watts on 160, but the cost of the vacuum variables is a real issue. February QST has an article on using mineral oil immersion to increase the voltage capability of variables in a 600M amplifier. The article does not include any hi-pot data, but indicates that the maximum capacitance went up a lot. Opinions? -- 73, Pete N4ZR Check out the Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com. For spots, please go to your favorite ARC V6 or VE7CC DX cluster node. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Compromise vertical loading questions
Yes no doubt, it seems if a persons personal agenda precedes their ability to read with any comprehension on this reflector so many times, here we go again. The discussion is about the placement of an additional loading coil and its influence while the radiator is already loaded by a capacitance hat. So who spreads misinformation? -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Yuri Blanarovich Here we go again, Tom spreading misinformation. IT IS important where the coil is placed in the loaded antenna. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Bad tower shunt capacitor
I have an omega matched 120 foot tower and I apparently have a bad vacuum variable capacitor. Upon applying more than about 300 watts, the SWR goes off scale. Tuning it out and trying again, yields the same thing. The question is which capacitor is the culprit. These are surplus Soviet caps obtained from the Ukraine and, as I recall, the larger value capacitor is the parallel one, not the series one. I could buy one of each and switch one at a time and have a spare left over. Any suggestions ? 73, Jamie WB4YDL Sent from my iPad _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Apology for QRM
All, I apologize for briefly QRMing the FT5 this evening. Mistakes were made; buttons were pushed. I will try to pay attention in the future. 73, geo - n4ua _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
I have an omega matched 120 foot tower and I apparently have a bad vacuum variable capacitor. Upon applying more than about 300 watts, the SWR goes off scale. Tuning it out and trying again, yields the same thing. The question is which capacitor is the culprit. These are surplus Soviet caps obtained from the Ukraine and, as I recall, the larger value capacitor is the parallel one, not the series one. I could buy one of each and switch one at a time and have a spare left over. Any suggestions ? Jamie, How do you know it is a capacitor and not something else? Normally vacuum capacitors are either good, have air, or are shorted. They short when a plate melts and stay shorted in that position or further meshed They have no return pull tension when they have no vacuum If the tuning is changing, maybe something else on the tower is arcing, like an insulator? _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Short receiving verticals question
Recent success here with 23-foot-high W8JI-style short receiving verticals in a 4-element broadside/endfire array using variable phasing has led me to make plans for other sets to cover additional directions. To maximize distance from existing and potential noise sources, and to allow for tighter endfire spacing, I chose to make these independent arrays rather than the classic 8-circle array. Since these will all be in a wooded area, I am considering using different elements without top loading wires, to avoid constant maintenance as falling tree limbs would break the wires. I've read of the 36-foot-high base-loaded elements ON4UN described in his book, and understand these would have a slightly narrower bandwidth than an element with top-hat wires. But what about an element loaded with a coil at the center or at the top? Would there be advantages to that approach that would come close to the short verticals with top-hat wires, or any serious disadvantages? 73/Jon AA1K _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
Thanks Steve: Not bad - I may try that ! :) The question in my mind was if there was an arc outside the caps, why would the SWR change ? Anyway, I may be missing something. I haven't been inside the cap box at the tower for many months so I'll get into it - may be something easy. 73, Jamie WB4YDL Sent from my iPad On Jan 29, 2014, at 7:11 PM, wb6r...@mac.com wrote: Have someone hit the key while you watch which one flashes over. Steve WB6RSE On Jan 29, 2014, at 4:26 PM, James C. Hall, MD wrote: Any suggestions ? -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Short receiving verticals question
On 1/29/2014 6:25 PM, Jon Zaimes AA1K wrote: I've read of the 36-foot-high base-loaded elements ON4UN described in his book, and understand these would have a slightly narrower bandwidth than an element with top-hat wires. But what about an element loaded with a coil at the center or at the top? Would there be advantages to that approach that would come close to the short verticals with top-hat wires, or any serious disadvantages? 73/Jon AA1K I once built a 4x2 fixed array using 30 foot verticals, the height chosen because I had a bunch of 30 foot long irrigation pipes. I not only did not use top loading, but I didn't resonate them with a coil either. Thus the signal was low, but usable. This array worked perfectly, with directivity as per theory. So I think you will be fine w/o top loading wires, especially if you use a resonator coil. The reason not to use a resonator coil is if you want to use the array on more than one band. My array had quarter wave end fire spacing on 80, and eighth wave spacing on 160. It even worked on the broadcast band with a little gain, but a lot of F/B ratio. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Submerging variable caps in oil as substitute for vacuum variables
Subject:Re: Topband: Submerging variable caps in oil as substitute for vacuum variables The author points out (correctly) the tempco issues with oil dielectric. Still I am intrigued by the thought of a remote tuning capacitor via hydraulic tubing :-). The capacitor plates could be as simple as two concentric cylinder conductors with appropriate spacers. I betcha crud collecting on the top of the oil would set voltage limit. Tim N3QE - The omega match for my shunt fed tower uses two 300 uF roughly 3000-volt variables I bought from Henry radio a few years ago. I think occasionally about running more than 100 watts on 160, but the cost of the vacuum variables is a real issue. February QST has an article on using mineral oil immersion to increase the voltage capability of variables in a 600M amplifier. The article does not include any hi-pot data, but indicates that the maximum capacitance went up a lot. Opinions? Tim, I have an oil filled variable capacitor that I picked up surplus many years ago. The spacing is about 0.01 inch, capacitance 1000 pF and if I remember correctly it hi-potted to around 5kV. I still have it. I am using 2 X 500pF @ 7.5kV vacuum variables in my Omega Shunt feed. I normally run 1500 watts out on 160. Top loaded 80 feet of Rohn 45G. Guyed with 6700 lb Phillystran. 73 de Price W0RI and Club Station W0CKC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
Jamie, The VSWR would change because the arc would change the impedance at the Arc point. From perhaps several hundred or thousand ohms to near Zero during the Arc.. 73, Price W0RI Thanks Steve: Not bad - I may try that ! :) The question in my mind was if there was an arc outside the caps, why would the SWR change ? Anyway, I may be missing something. I haven't been inside the cap box at the tower for many months so I'll get into it - may be something easy. 73, Jamie WB4YDL Sent from my iPad On Jan 29, 2014, at 7:11 PM, wb6r...@mac.com wrote: Have someone hit the key while you watch which one flashes over. Steve WB6RSE _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Compromise vertical loading questions
Amen Merv, You hit the nail on the head ! ! 73 Price W0RI Yes no doubt, it seems if a persons personal agenda precedes their ability to read with any comprehension on this reflector so many times, here we go again. The discussion is about the placement of an additional loading coil and its influence while the radiator is already loaded by a capacitance hat. So who spreads misinformation? -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Yuri Blanarovich Here we go again, Tom spreading misinformation. IT IS important where the coil is placed in the loaded antenna. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
