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#1
June 2nd 05, 11:27 PM
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"John Smith" wrote in message ... Dave: The T-Match will still show a favor in signal launch because of the imbalance of the gamma rods on one side, on a beam this could even be manipulated to ones favor--not as likely on a monopole... just looking for a way to completely balance the field pattern... I just thought someone had most likely done something like this before... if I don't hear of anyone, will shove some various sized drain, stove pipe, soldered cans, etc. over a 1/2 monopole in place of the gamma rod and check it out this weekend... Warmest regards, John How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Dale W4OP |
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#2
June 2nd 05, 11:41 PM
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In article tJLne.13595$Vm4.9195@trnddc01,
Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Seems to me that a T directly from coax could show some amount of imbalance. The center-conductor current would have only one pathway to feed (the T), while the shield current would have two (the other side of the T, and back down the feedline). If the outside of the feedline was an integral number of halfwaves down to the point at which it's grounded, there might be enough current flow on the outside of the feedline to disturb the balance and change the pattern somewhat. Sticking a half-wave coax balun at the input of the T ought to resolve this pretty well, no? -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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#3
June 3rd 05, 12:38 AM
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"Dave Platt" wrote in message ... In article tJLne.13595$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Seems to me that a T directly from coax could show some amount of imbalance. The center-conductor current would have only one pathway to feed (the T), while the shield current would have two (the other side of the T, and back down the feedline). If the outside of the feedline was an integral number of halfwaves down to the point at which it's grounded, there might be enough current flow on the outside of the feedline to disturb the balance and change the pattern somewhat. Sticking a half-wave coax balun at the input of the T ought to resolve this pretty well, no? yes, that is how most of them i have seen work. a 1/2 wave phasing line is used to feed the 'opposite' side of the T making it properly balanced. |
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#4
June 3rd 05, 02:46 AM
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"Dave Platt" wrote in message ... In article tJLne.13595$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Check out any of the antenna handbooks for a Tee match. The driven element is insulated from the boom and split in the middle. Each side of the Tee taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1 coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms unbalanced. Dale W4OP |
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#5
June 3rd 05, 02:58 AM
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Dale:
Yes, someone injected a T-Match in here, but no real interest in a T-Match... Warmest regards, John "Dale Parfitt" wrote in message news:ODOne.7695$vK5.2782@trnddc03... "Dave Platt" wrote in message ... In article tJLne.13595$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Check out any of the antenna handbooks for a Tee match. The driven element is insulated from the boom and split in the middle. Each side of the Tee taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1 coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms unbalanced. Dale W4OP |
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#6
June 3rd 05, 01:01 PM
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I should have pointed out, a T-Match requires a dipole, a few seem to
miss I had previously noted this is a monopole in question... a T-Match would unbalance the RF RADIATION PATTERN of a dipole in the same way a gamma does a monopole, there would be no gain from using a T-Match in place of a gamma, EVEN if it could be done here... I suppose you might be able to mount the bottom of T-Match on the mast holding the monopole--but then, that is another experiment for another day... Warmest regards, John "John Smith" wrote in message ... Dale: Yes, someone injected a T-Match in here, but no real interest in a T-Match... Warmest regards, John "Dale Parfitt" wrote in message news:ODOne.7695$vK5.2782@trnddc03... "Dave Platt" wrote in message ... In article tJLne.13595$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Check out any of the antenna handbooks for a Tee match. The driven element is insulated from the boom and split in the middle. Each side of the Tee taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1 coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms unbalanced. Dale W4OP |
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#7
June 3rd 05, 01:43 PM
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John Smith wrote:
I should have pointed out, a T-Match requires a dipole, a few seem to miss I had previously noted this is a monopole in question... Is there any difference in a 1/2WL monopole element and a 1/2WL dipole element sans the T-Match? I can't think of any. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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#8
June 3rd 05, 01:50 PM
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Not that I am aware of, only thing is there is no where to "hang" that
T-Match--well, the mast I mentioned... and the fact the monopole is absent the bottom half of a dipole element... this is especially notable if the bottom end of the monopole is sitting on the ground... that tends to remove all confusion... grin Warmest regards, John "Cecil Moore" wrote in message ... John Smith wrote: I should have pointed out, a T-Match requires a dipole, a few seem to miss I had previously noted this is a monopole in question... Is there any difference in a 1/2WL monopole element and a 1/2WL dipole element sans the T-Match? I can't think of any. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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#9
June 3rd 05, 11:42 PM
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John Smith wrote: I should have pointed out, a T-Match requires a dipole, a few seem to miss I had previously noted this is a monopole in question... a T-Match would unbalance the RF RADIATION PATTERN of a dipole in the same way a gamma does a monopole, there would be no gain from using a T-Match in place of a gamma, EVEN if it could be done here... I suppose you might be able to mount the bottom of T-Match on the mast holding the monopole--but then, that is another experiment for another day... Warmest regards, John I've been thinking about a delta type match as a way to couple to a 1/2 wave radiator. Might be interesting. ac6xg "John Smith" wrote in message ... Dale: Yes, someone injected a T-Match in here, but no real interest in a T-Match... Warmest regards, John "Dale Parfitt" wrote in message news:ODOne.7695$vK5.2782@trnddc03... "Dave Platt" wrote in message ... In article tJLne.13595$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Check out any of the antenna handbooks for a Tee match. The driven element is insulated from the boom and split in the middle. Each side of the Tee taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1 coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms unbalanced. Dale W4OP |
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#10
June 4th 05, 01:20 AM
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might just work, if the total element length is 1 wave! and in a dipole
configuration... Warmest regards, John "Jim Kelley" wrote in message ... John Smith wrote: I should have pointed out, a T-Match requires a dipole, a few seem to miss I had previously noted this is a monopole in question... a T-Match would unbalance the RF RADIATION PATTERN of a dipole in the same way a gamma does a monopole, there would be no gain from using a T-Match in place of a gamma, EVEN if it could be done here... I suppose you might be able to mount the bottom of T-Match on the mast holding the monopole--but then, that is another experiment for another day... Warmest regards, John I've been thinking about a delta type match as a way to couple to a 1/2 wave radiator. Might be interesting. ac6xg "John Smith" wrote in message ... Dale: Yes, someone injected a T-Match in here, but no real interest in a T-Match... Warmest regards, John "Dale Parfitt" wrote in message news:ODOne.7695$vK5.2782@trnddc03... "Dave Platt" wrote in message ... In article tJLne.13595$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Check out any of the antenna handbooks for a Tee match. The driven element is insulated from the boom and split in the middle. Each side of the Tee taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1 coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms unbalanced. Dale W4OP |
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