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Gamma Matching Question
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match. I understand that a gamma match will work over a wide range of frequencies. I hope to work a number of bands using the same loop. My question is -- when I'm ready to test the antenna do I adjust the gamma match at the lowest frequency I plan to use, or the highest? I have considered other forms of coupling the rig to the transmitter but prefer to use the gamma match. Thanks in advance for any assistance or advice in this matter. Irv VE6BP |
#2
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Gamma Matching Question
Irv Finkleman wrote:
I am planning to build a magnetic loop antenna and feed it by means of a gamma match. I understand that a gamma match will work over a wide range of frequencies. I hope to work a number of bands using the same loop. The gamma match principle will work over a wide range of frequencies but a given gamma match is rather narrow banded. Unless your gamma match is really mechanically clever like perhaps the SteppIR antennas, it isn't going to cover multiple bands. Some references for study: http://www.bcpink.com/KB3IFH/files/D...%20article.pdf http://www.k1ttt.net/technote/gamma.html -- Jim Pennino |
#3
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Gamma Matching Question
On Sat, 21 Sep 2013 11:50:40 -0600, Irv Finkleman wrote:
I am planning to build a magnetic loop antenna and feed it by means of a gamma match. I understand that a gamma match will work over a wide range of frequencies. Your understanding is in error. At best a gamma match will "work well" over a 1-2% freq. range -- for selected definitions of "work well. Jonesy -- Marvin L Jones | jonz | W3DHJ | linux 38.24N 104.55W | @ config.com | Jonesy | OS/2 * Killfiling google & XXXXbanter.com: jonz.net/ng.htm |
#4
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Gamma Matching Question
Thanks to Jim and Jonesy -- I'm not very familiar with
all the ins and outs of Gamma matching, but in a number of cases of Magnetic Loops where the loop covers a number of bands e.g. 80-15m, 80-30M, the builders used a Gamma match which when set needs no adjustment between bands. Perhaps the Magnetic Loop has different properties, although the authors of the articles claimed the matching portion was a 'form of Gamma Match' and in one case referred to the matching portion as a form of autotransformer which I interpret to mean a non-circular feed loop of sorts. In one loop design by Peter Parker VK3YE whose loop covers 160-15 meters, the author advised me (when I queried the Gamma question to him) that the gamma when set as designed serves all bands well. In other designs the gamma match or whatever it might be, seems to work and did not seem to be a problem or I think it might have been commented on by the authors. I will be investigating all these things soon -- I have just recovered over a few years of some pretty heavy abdominal surgeries and will be moving to a senior's residence where I will have a balcony to work from. It will be nice to get back on the air again after having had to sell my house after the first surgery where I had room for all different forms of antennas. Now I will be back on the air again but will have to work under certain restrictions such as no wires to nearby trees and so forth. A magnetic loop or some form of windowsill antenna will likely be my best bets. I'm looking forward to the experience! I've always maintained to other old timers who moved into condos where there restrictions that there would always be some way to get on the air -- now I'm going to have to walk the talk myself! One way or another I'm not going to give up 55 years of hamming -- even if I can only work across town! I'm shooting for multiband 80-10M operation -- or bust! (Touch wood!) Thanks, Irv VE6BP .. "Allodoxaphobia" wrote in message t... On Sat, 21 Sep 2013 11:50:40 -0600, Irv Finkleman wrote: I am planning to build a magnetic loop antenna and feed it by means of a gamma match. I understand that a gamma match will work over a wide range of frequencies. Your understanding is in error. At best a gamma match will "work well" over a 1-2% freq. range -- for selected definitions of "work well. Jonesy -- Marvin L Jones | jonz | W3DHJ | linux 38.24N 104.55W | @ config.com | Jonesy | OS/2 * Killfiling google & XXXXbanter.com: jonz.net/ng.htm |
#5
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Gamma Matching Question
Irv Finkleman wrote:
Thanks to Jim and Jonesy -- I'm not very familiar with all the ins and outs of Gamma matching, but in a number of cases of Magnetic Loops where the loop covers a number of bands e.g. 80-15m, 80-30M, the builders used a Gamma match which when set needs no adjustment between bands. Perhaps the Magnetic Loop has different properties, although the authors of the articles claimed the matching portion was a 'form of Gamma Match' and in one case referred to the matching portion as a form of autotransformer which I interpret to mean a non-circular feed loop of sorts. In one loop design by Peter Parker VK3YE whose loop covers 160-15 meters, the author advised me (when I queried the Gamma question to him) that the gamma when set as designed serves all bands well. In other designs the gamma match or whatever it might be, seems to work and did not seem to be a problem or I think it might have been commented on by the authors. I will be investigating all these things soon -- I have just recovered over a few years of some pretty heavy abdominal surgeries and will be moving to a senior's residence where I will have a balcony to work from. It will be nice to get back on the air again after having had to sell my house after the first surgery where I had room for all different forms of antennas. Now I will be back on the air again but will have to work under certain restrictions such as no wires to nearby trees and so forth. A magnetic loop or some form of windowsill antenna will likely be my best bets. I'm looking forward to the experience! I've always maintained to other old timers who moved into condos where there restrictions that there would always be some way to get on the air -- now I'm going to have to walk the talk myself! One way or another I'm not going to give up 55 years of hamming -- even if I can only work across town! I'm shooting for multiband 80-10M operation -- or bust! (Touch wood!) Thanks, Irv VE6BP The easiest way to achieve that is get yourself one of the autotunners which will tune just about anything. The high power ones tend to be expensive but if you are running the typical rig barefoot in the 100 watt range they are not that expensive these days. I have a vertical with an autotunner that covers all bands from 80 to 10, including of course 30, 17, and 12. I contemplated using a loop instead of a vertical but the vertical was easier to put up where I live. -- Jim Pennino |
#6
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Gamma Matching Question
In article ,
"Irv Finkleman" wrote: will be moving to a senior's residence where I will have a balcony to work from. Irv- Go ahead and try the loop. At least you will be on the air, and you may be surprised how well it works. I once lived in an apartment where a previous resident had installed a trucker's mirror antenna mount on the metal balcony rail. I used it with mobile whips to get on HF. The metal rail worked as a ground plane, and my TS-690S built-in tuner was able to match it. You might also consider dipoles made from mobile whips. I have had good luck, especially on higher bands. I currently have an "Octopus" antenna made from four sets of mobile whips fed in parallel. It might not fit on your balcony, but fits inside my attic. (The Octopus was published in the December, 2007, issue of QST.) 73, Fred K4DII |
#7
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Gamma Matching Question
OOps! I sent replies direct to Fred instead of the newsgroup!
Here's a repeat of one! ------------------ Thanks Fred. I am determined to experiment with the Magnetic Loop only because I haven't worked with one before. I am also keeping in mind a windowsill antenna as a backup, and also in case I run into problems getting the Loop going. I've previously worked the gamut of antennas from the old 'Gotham Vertical' which was a classic back in the fifties, through all kinds of dipoles, towers beams and rotors, random wires, folded Marconis, and such but never a loop. The Magnetic Loop is a fairly new concept that intrigues me, and unlike a mobile whip or other compromise antenna, it is 'complete' in itself and a lot of guys are giving it pretty good reports. As well, it will serve on a balcony without being overrly obtrusive. Time will tell but I'm going to have some fun! I'll have to look for the Octopus in the QST Archives, not to build one but to have a look at it. Tks agn es 73 Irv VE6BP. "Fred McKenzie" wrote in message ... In article , "Irv Finkleman" wrote: will be moving to a senior's residence where I will have a balcony to work from. Irv- Go ahead and try the loop. At least you will be on the air, and you may be surprised how well it works. I once lived in an apartment where a previous resident had installed a trucker's mirror antenna mount on the metal balcony rail. I used it with mobile whips to get on HF. The metal rail worked as a ground plane, and my TS-690S built-in tuner was able to match it. You might also consider dipoles made from mobile whips. I have had good luck, especially on higher bands. I currently have an "Octopus" antenna made from four sets of mobile whips fed in parallel. It might not fit on your balcony, but fits inside my attic. (The Octopus was published in the December, 2007, issue of QST.) 73, Fred K4DII |
#8
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Gamma Matching Question
On 9/21/2013 12:50 PM, Irv Finkleman wrote:
I am planning to build a magnetic loop antenna and feed it by means of a gamma match. I understand that a gamma match will work over a wide range of frequencies. I hope to work a number of bands using the same loop. My question is -- when I'm ready to test the antenna do I adjust the gamma match at the lowest frequency I plan to use, or the highest? I have considered other forms of coupling the rig to the transmitter but prefer to use the gamma match. Thanks in advance for any assistance or advice in this matter. Irv VE6BP I gave up the idea of a magnetic antenna when I found how much the tunable capacitor cost when using 1500 watts. Ouch |
#9
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Gamma Matching Question
"Irv Finkleman" wrote in message ... I am planning to build a magnetic loop antenna and feed it by means of a gamma match. I understand that a gamma match will work over a wide range of frequencies. I hope to work a number of bands using the same loop. My question is -- when I'm ready to test the antenna do I adjust the gamma match at the lowest frequency I plan to use, or the highest? I have considered other forms of coupling the rig to the transmitter but prefer to use the gamma match. Thanks in advance for any assistance or advice in this matter. Irv VE6BP The US Coast Guard has used circular loop antennas for transmitting. I remember noting them when I did EMI inspections on several Coast Guard cutters in the 1990's. Perhaps that knowledge will lead you in the direction of existing documentation on the methods they used. All of my data is long gone but I did see this guy's page on-line: http://www.aa5tb.com/loop.html Good luck. |
#10
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Gamma Matching Question
On 9/21/2013 12:50 PM, Irv Finkleman wrote:
I am planning to build a magnetic loop antenna and feed it by means of a gamma match. I understand that a gamma match will work over a wide range of frequencies. I hope to work a number of bands using the same loop. My question is -- when I'm ready to test the antenna do I adjust the gamma match at the lowest frequency I plan to use, or the highest? I have considered other forms of coupling the rig to the transmitter but prefer to use the gamma match. Thanks in advance for any assistance or advice in this matter. Irv VE6BP Hi, Irv - See if this link is of any help to you... http://www.vk1od.net/antenna/GammaMatch/gbs.htm John KD5YI |
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