|
Gamma tube?
From working with the gamma match in real life--I have noticed it favors
launching the signal from the side of the DE which has the gamma. Now in playing with the gamma formulas, I wondered... What if the gamma rod is replaced with a "gamma tube", same set up as the normal gamma, except the the rod is now a tube surrounding the element which is being fed? Something of a "concentric match", I am guessing the formula to compute concentric line Zo would come into play here, or a near equiv... purpose would be to get rid of the favored increase in signal from the side containing the gamma... I know someone is going to suggest EZNEC--however, I am not good at drawing a tube with it!!!! Warmest regards, John -- Watching the cutting edge of yesterday replay--in virtual reality, right before my eyes--in real time! Thirty year old technology--wasn't it amazing? |
why not a T match. simpler to build and adjust than a gamma, completely dc
grounded, and balanced. "John Smith" wrote in message ... From working with the gamma match in real life--I have noticed it favors launching the signal from the side of the DE which has the gamma. Now in playing with the gamma formulas, I wondered... What if the gamma rod is replaced with a "gamma tube", same set up as the normal gamma, except the the rod is now a tube surrounding the element which is being fed? Something of a "concentric match", I am guessing the formula to compute concentric line Zo would come into play here, or a near equiv... purpose would be to get rid of the favored increase in signal from the side containing the gamma... I know someone is going to suggest EZNEC--however, I am not good at drawing a tube with it!!!! Warmest regards, John -- Watching the cutting edge of yesterday replay--in virtual reality, right before my eyes--in real time! Thirty year old technology--wasn't it amazing? |
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 "Dave" wrote in message ... why not a T match. simpler to build and adjust than a gamma, completely dc grounded, and balanced. "John Smith" wrote in message ... From working with the gamma match in real life--I have noticed it favors launching the signal from the side of the DE which has the gamma. Now in playing with the gamma formulas, I wondered... What if the gamma rod is replaced with a "gamma tube", same set up as the normal gamma, except the the rod is now a tube surrounding the element which is being fed? Something of a "concentric match", I am guessing the formula to compute concentric line Zo would come into play here, or a near equiv... purpose would be to get rid of the favored increase in signal from the side containing the gamma... I know someone is going to suggest EZNEC--however, I am not good at drawing a tube with it!!!! Warmest regards, John -- Watching the cutting edge of yesterday replay--in virtual reality, right before my eyes--in real time! Thirty year old technology--wasn't it amazing? |
John Smith wrote:
The T-Match will still show a favor in signal launch because of the imbalance of the gamma rods on one side, ... A T-match is balanced because it is right+left gamma matches, i.e. gamma rods on both sides with two equal series caps (or tube caps). -- 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 =---- |
if you do a T match like telrex used on their monobanders there is no
favored side, the two T arms were fed with a 1/2 wave phasing line and required no capacitor so everything was at dc ground. very simple to build and definately balanced. "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 "Dave" wrote in message ... why not a T match. simpler to build and adjust than a gamma, completely dc grounded, and balanced. "John Smith" wrote in message ... From working with the gamma match in real life--I have noticed it favors launching the signal from the side of the DE which has the gamma. Now in playing with the gamma formulas, I wondered... What if the gamma rod is replaced with a "gamma tube", same set up as the normal gamma, except the the rod is now a tube surrounding the element which is being fed? Something of a "concentric match", I am guessing the formula to compute concentric line Zo would come into play here, or a near equiv... purpose would be to get rid of the favored increase in signal from the side containing the gamma... I know someone is going to suggest EZNEC--however, I am not good at drawing a tube with it!!!! Warmest regards, John -- Watching the cutting edge of yesterday replay--in virtual reality, right before my eyes--in real time! Thirty year old technology--wasn't it amazing? |
Cecil:
Sorry, didn't mean that sort "balance"--as in a balanced antenna... you are right to make me be more specific... ....rather, I mean in the radiated rf field pattern of the antenna itself--because the T-Match is only on one side of the driven element--the radiation will not be completely circular (as in a vertical)--and will begin formation of a stronger pattern in one direction over all other directions on a compass, this is in reference to a vertical monopole, but still would be in effect in a horizontal version, in affecting a stronger pattern in one direction.... (and of course, there is no such thing as a "perfect" pattern, just degrees of more or less.) Warmest regards, John "Cecil Moore" wrote in message ... John Smith wrote: The T-Match will still show a favor in signal launch because of the imbalance of the gamma rods on one side, ... A T-match is balanced because it is right+left gamma matches, i.e. gamma rods on both sides with two equal series caps (or tube caps). -- 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 =---- |
Dave:
Yes, the very bottom of the monopole with a concentric "gamma tube" would be at ground level (NOT the BOTTOM of the "gamma tube", the top of the "gamma tube" would be connected to DE with a shorting disk or shorting strap and would be some distance up the DE, the bottom of the "gamma tube" would connect to a series cap to tune out Jx of the "gamma tube", and then to the center conductor of the coax.) and coax shield is placed at the level of the bottom of the DE monopole... Warmest regards, John "Dave" wrote in message ... if you do a T match like telrex used on their monobanders there is no favored side, the two T arms were fed with a 1/2 wave phasing line and required no capacitor so everything was at dc ground. very simple to build and definately balanced. "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 "Dave" wrote in message ... why not a T match. simpler to build and adjust than a gamma, completely dc grounded, and balanced. "John Smith" wrote in message ... From working with the gamma match in real life--I have noticed it favors launching the signal from the side of the DE which has the gamma. Now in playing with the gamma formulas, I wondered... What if the gamma rod is replaced with a "gamma tube", same set up as the normal gamma, except the the rod is now a tube surrounding the element which is being fed? Something of a "concentric match", I am guessing the formula to compute concentric line Zo would come into play here, or a near equiv... purpose would be to get rid of the favored increase in signal from the side containing the gamma... I know someone is going to suggest EZNEC--however, I am not good at drawing a tube with it!!!! Warmest regards, John -- Watching the cutting edge of yesterday replay--in virtual reality, right before my eyes--in real time! Thirty year old technology--wasn't it amazing? |
"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 |
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! |
but a vertical monopole about 1/4 wave long doesn't even need a matching
system in most cases... unless you are a real perfectionist. just what are you trying to build here anyway? "John Smith" wrote in message ... Cecil: Sorry, didn't mean that sort "balance"--as in a balanced antenna... you are right to make me be more specific... ...rather, I mean in the radiated rf field pattern of the antenna itself--because the T-Match is only on one side of the driven element--the radiation will not be completely circular (as in a vertical)--and will begin formation of a stronger pattern in one direction over all other directions on a compass, this is in reference to a vertical monopole, but still would be in effect in a horizontal version, in affecting a stronger pattern in one direction.... (and of course, there is no such thing as a "perfect" pattern, just degrees of more or less.) Warmest regards, John "Cecil Moore" wrote in message ... John Smith wrote: The T-Match will still show a favor in signal launch because of the imbalance of the gamma rods on one side, ... A T-match is balanced because it is right+left gamma matches, i.e. gamma rods on both sides with two equal series caps (or tube caps). -- 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 =---- |
"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. |
Dave:
I had mentioned 1/2 wave monopole above--right now I am in the "1/2 wave vertical monopole period of life"... grin... freq 10 meter on up... Warmest regards, John "Dave" wrote in message ... but a vertical monopole about 1/4 wave long doesn't even need a matching system in most cases... unless you are a real perfectionist. just what are you trying to build here anyway? "John Smith" wrote in message ... Cecil: Sorry, didn't mean that sort "balance"--as in a balanced antenna... you are right to make me be more specific... ...rather, I mean in the radiated rf field pattern of the antenna itself--because the T-Match is only on one side of the driven element--the radiation will not be completely circular (as in a vertical)--and will begin formation of a stronger pattern in one direction over all other directions on a compass, this is in reference to a vertical monopole, but still would be in effect in a horizontal version, in affecting a stronger pattern in one direction.... (and of course, there is no such thing as a "perfect" pattern, just degrees of more or less.) Warmest regards, John "Cecil Moore" wrote in message ... John Smith wrote: The T-Match will still show a favor in signal launch because of the imbalance of the gamma rods on one side, ... A T-match is balanced because it is right+left gamma matches, i.e. gamma rods on both sides with two equal series caps (or tube caps). -- 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 =---- |
"Dave Platt" wrote in message ... In article tJLne.13595$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Check out any of the antenna handbooks for a Tee match. The driven element is insulated from the boom and split in the middle. Each side of the Tee taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1 coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms unbalanced. Dale W4OP |
Dale:
Yes, someone injected a T-Match in here, but no real interest in a T-Match... Warmest regards, John "Dale Parfitt" wrote in message news:ODOne.7695$vK5.2782@trnddc03... "Dave Platt" wrote in message ... In article tJLne.13595$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Check out any of the antenna handbooks for a Tee match. The driven element is insulated from the boom and split in the middle. Each side of the Tee taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1 coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms unbalanced. Dale W4OP |
I should have pointed out, a T-Match requires a dipole, a few seem to
miss I had previously noted this is a monopole in question... a T-Match would unbalance the RF RADIATION PATTERN of a dipole in the same way a gamma does a monopole, there would be no gain from using a T-Match in place of a gamma, EVEN if it could be done here... I suppose you might be able to mount the bottom of T-Match on the mast holding the monopole--but then, that is another experiment for another day... Warmest regards, John "John Smith" wrote in message ... Dale: Yes, someone injected a T-Match in here, but no real interest in a T-Match... Warmest regards, John "Dale Parfitt" wrote in message news:ODOne.7695$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 |
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 =---- |
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 =---- |
.... err, not to be confused with a "dipole beam", which is better
referred to as a "two element beam" to remove all confusion... grin Warmest regards, John "John Smith" wrote in message ... 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 =---- |
Dale Parfitt wrote:
"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 Dale Was that you I worked while mobile on 6 yesterday or the day before? Sounds like the call I remember. tom K0TAR |
in other words i think he is trying to make a J pole into a coaxial
arrangement where the short part of the J wraps all the way around the pole. personally it sounds like a lot of work to get rid of some small assymetry caused by the gamma rod. the easier solution is a plain vertical with a tuner to make the transmitter happy. "John Smith" wrote in message ... ... err, not to be confused with a "dipole beam", which is better referred to as a "two element beam" to remove all confusion... grin Warmest regards, John "John Smith" wrote in message ... 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 =---- |
why not just a rusty coat hanger and some bailing wire? grin
John "Dave" wrote in message ... in other words i think he is trying to make a J pole into a coaxial arrangement where the short part of the J wraps all the way around the pole. personally it sounds like a lot of work to get rid of some small assymetry caused by the gamma rod. the easier solution is a plain vertical with a tuner to make the transmitter happy. "John Smith" wrote in message ... ... err, not to be confused with a "dipole beam", which is better referred to as a "two element beam" to remove all confusion... grin Warmest regards, John "John Smith" wrote in message ... 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 =---- |
"Tom Ring" wrote in message .. . Dale Parfitt wrote: "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 Dale Was that you I worked while mobile on 6 yesterday or the day before? Sounds like the call I remember. tom K0TAR Hi Tom, I knew the band was open because of 88-108 stations booming in, but my rotor and remote antenna switch wires to the tower are temporarily disconnected while we build a 180 ton rock wall behind the house. I'll be back on this weekend. Dale W4OP |
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$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Check out any of the antenna handbooks for a Tee match. The driven element is insulated from the boom and split in the middle. Each side of the Tee taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1 coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms unbalanced. Dale W4OP |
might just work, if the total element length is 1 wave! and in a dipole
configuration... Warmest regards, John "Jim Kelley" wrote in message ... John Smith wrote: I should have pointed out, a T-Match requires a dipole, a few seem to miss I had previously noted this is a monopole in question... a T-Match would unbalance the RF RADIATION PATTERN of a dipole in the same way a gamma does a monopole, there would be no gain from using a T-Match in place of a gamma, EVEN if it could be done here... I suppose you might be able to mount the bottom of T-Match on the mast holding the monopole--but then, that is another experiment for another day... Warmest regards, John I've been thinking about a delta type match as a way to couple to a 1/2 wave radiator. Might be interesting. ac6xg "John Smith" wrote in message ... Dale: Yes, someone injected a T-Match in here, but no real interest in a T-Match... Warmest regards, John "Dale Parfitt" wrote in message news:ODOne.7695$vK5.2782@trnddc03... "Dave Platt" wrote in message ... In article tJLne.13595$Vm4.9195@trnddc01, Dale Parfitt wrote: How can a T match have show a bias- it is balanced. Virtually all the serious EME arrays use this matching technique and show the major lobe dead off the front. Are they feeding directly off of the coax, or do they use a halfwave (or other) balun between the coax and the T? Check out any of the antenna handbooks for a Tee match. The driven element is insulated from the boom and split in the middle. Each side of the Tee taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1 coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms unbalanced. Dale W4OP |
.... however, would still distort radiation pattern due to the match on
one side... perfect symmetry prompted me to begin this line of thought and tweaking the equations... Warmest regards, John "John Smith" wrote in message ... might just work, if the total element length is 1 wave! and in a dipole configuration... Warmest regards, John "Jim Kelley" wrote in message ... John Smith wrote: I should have pointed out, a T-Match requires a dipole, a few seem to miss I had previously noted this is a monopole in question... a T-Match would unbalance the RF RADIATION PATTERN of a dipole in the same way a gamma does a monopole, there would be no gain from using a T-Match in place of a gamma, EVEN if it could be done here... I suppose you might be able to mount the bottom of T-Match on the mast holding the monopole--but then, that is another experiment for another day... Warmest regards, John I've been thinking about a delta type match as a way to couple to a 1/2 wave radiator. Might be interesting. ac6xg "John Smith" wrote in message ... Dale: Yes, someone injected a T-Match in here, but no real interest in a T-Match... Warmest regards, John "Dale Parfitt" wrote in message news:ODOne.7695$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 |
John Smith wrote: might just work, if the total element length is 1 wave! and in a dipole configuration... You're thinking too far outside the box. Reel it back in a smidge. :-) ac6xg |
Jim:
Well, I have found terminology interesting. And, depends on whose you use, there is ARRL of course, then there are a bunch of in-house tech docs from industry. Take what I have been accustomed to calling a 1/2 wave monopole--for example: on 10 meters, it is about a 16 foot metal length and end fed. An EFHWA. Most frequently fed through an L-Match or 1/4 wave matching section--sometimes uniquely though an unun. However, if you attempt to feed it in the middle, it suddenly becomes a dipole, the equiv of two 8 ft-1/4 wave monopoles connected at there bases, and would take a unique feed I am not familiar with, as each 1/4 wave section would need be fed out of phase--and this would be difficult with the impedance so close to the feedline (coax in this case) and having the 1/4 monopoles connected (notice, I didn't say impossible! grin.) Spilt the 1/2 monopole and center feed it and it becomes two 1/4 wave monopoles (commonly referred to as a 1/2 wave dipole) and can be center fed with convention means quite easily, as a dipole (indeed, many feed them directly from coax--the more picky through a isolation balun or 1/4 wave section.) However, two 1/2 monopoles, connected at their bases (actually a 1 wave length single element) begins to accept center feeding with quite conventional means (ant feed point is high impedance), although in ARRL literature this would be referred to as 1 wave dipole, still it could be modeled as two 1/2 wave monopoles being fed out of phase. All I am concentrating on is the EFHWA (and, if setup right requires no counterpoise), and various means of feeding it, modifications and experiments... Warmest regards, John "Jim Kelley" wrote in message ... John Smith wrote: might just work, if the total element length is 1 wave! and in a dipole configuration... You're thinking too far outside the box. Reel it back in a smidge. :-) ac6xg |
I could be wrong, but here's what I was getting at. You should be able
to vary the feedpoint impedance, where ever the feedpoint happens to be (in this case, the end), by varying the distance between the attachment points of the two conductors of the feedline. The closer they are together, naturally, the lower the impedance. It should be possible to find a match in this way. Part B would be to keep the feedline from trying to radiate. ac6xg John Smith wrote: Jim: Well, I have found terminology interesting. And, depends on whose you use, there is ARRL of course, then there are a bunch of in-house tech docs from industry. Take what I have been accustomed to calling a 1/2 wave monopole--for example: on 10 meters, it is about a 16 foot metal length and end fed. An EFHWA. Most frequently fed through an L-Match or 1/4 wave matching section--sometimes uniquely though an unun. However, if you attempt to feed it in the middle, it suddenly becomes a dipole, the equiv of two 8 ft-1/4 wave monopoles connected at there bases, and would take a unique feed I am not familiar with, as each 1/4 wave section would need be fed out of phase--and this would be difficult with the impedance so close to the feedline (coax in this case) and having the 1/4 monopoles connected (notice, I didn't say impossible! grin.) Spilt the 1/2 monopole and center feed it and it becomes two 1/4 wave monopoles (commonly referred to as a 1/2 wave dipole) and can be center fed with convention means quite easily, as a dipole (indeed, many feed them directly from coax--the more picky through a isolation balun or 1/4 wave section.) However, two 1/2 monopoles, connected at their bases (actually a 1 wave length single element) begins to accept center feeding with quite conventional means (ant feed point is high impedance), although in ARRL literature this would be referred to as 1 wave dipole, still it could be modeled as two 1/2 wave monopoles being fed out of phase. All I am concentrating on is the EFHWA (and, if setup right requires no counterpoise), and various means of feeding it, modifications and experiments... Warmest regards, John "Jim Kelley" wrote in message ... John Smith wrote: might just work, if the total element length is 1 wave! and in a dipole configuration... You're thinking too far outside the box. Reel it back in a smidge. :-) ac6xg |
Jim:
Could be... by the time I am done with the venerable half-wave-end-fed I just might try it--I wasn't being picky, just explaining how I was attacking the problem... I don't mind side excursions of thought--your observations/suggestions are noted... thanks! Warmest regards, John "Jim Kelley" wrote in message ... I could be wrong, but here's what I was getting at. You should be able to vary the feedpoint impedance, where ever the feedpoint happens to be (in this case, the end), by varying the distance between the attachment points of the two conductors of the feedline. The closer they are together, naturally, the lower the impedance. It should be possible to find a match in this way. Part B would be to keep the feedline from trying to radiate. ac6xg John Smith wrote: Jim: Well, I have found terminology interesting. And, depends on whose you use, there is ARRL of course, then there are a bunch of in-house tech docs from industry. Take what I have been accustomed to calling a 1/2 wave monopole--for example: on 10 meters, it is about a 16 foot metal length and end fed. An EFHWA. Most frequently fed through an L-Match or 1/4 wave matching section--sometimes uniquely though an unun. However, if you attempt to feed it in the middle, it suddenly becomes a dipole, the equiv of two 8 ft-1/4 wave monopoles connected at there bases, and would take a unique feed I am not familiar with, as each 1/4 wave section would need be fed out of phase--and this would be difficult with the impedance so close to the feedline (coax in this case) and having the 1/4 monopoles connected (notice, I didn't say impossible! grin.) Spilt the 1/2 monopole and center feed it and it becomes two 1/4 wave monopoles (commonly referred to as a 1/2 wave dipole) and can be center fed with convention means quite easily, as a dipole (indeed, many feed them directly from coax--the more picky through a isolation balun or 1/4 wave section.) However, two 1/2 monopoles, connected at their bases (actually a 1 wave length single element) begins to accept center feeding with quite conventional means (ant feed point is high impedance), although in ARRL literature this would be referred to as 1 wave dipole, still it could be modeled as two 1/2 wave monopoles being fed out of phase. All I am concentrating on is the EFHWA (and, if setup right requires no counterpoise), and various means of feeding it, modifications and experiments... Warmest regards, John "Jim Kelley" wrote in message ... John Smith wrote: might just work, if the total element length is 1 wave! and in a dipole configuration... You're thinking too far outside the box. Reel it back in a smidge. :-) ac6xg |
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