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More data on my antenna
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Hash: SHA1 The weekend was beautiful, so I was able to do some outside work. I measured the antenna's impedance over 40m, then shortened the 40m legs by two feet each. I then measured the antenna's impedance again, and came up with numbers more closely resembling what I'd expect: Frequency Resistance Reactance Impedance 7.00 14 6 15.2 7.05 18 15 23.4 7.10 18 21 27.7 7.15 21 20 29.0 7.20 24 27 36.1 7.25 28 36 45.6 7.30 28 43 51.3 These measurements were done using a slightly different method. This time, I set the noise bridge for R=3D50 X=3D0 with the power off, then tuned the drive on my receiver for maximum noise before powering on the noise bridge and finding the null. The noise bridge manual is not as detailed as I would like, and it's not clear what the "proper" method is, but this produces reasonable results. The impedance is well within a 2:1 match throughout the voice segment, and a 3:1 match across the entire band. In other news, I happened to tune across 20m for the last five minutes of the Virginia QSO Party, and I made two contacts (NC4S and N4NW). I feel better about the performance of my antenna on that band, but I really hope that it's because the tuning somehow helped, and not that contesters are the only ones willing to dig into the noise. So it seems like I'm on the right track. I am going to try lengthening the antenna by six inches and doing another round of testing before moving on to the second set of legs, unless someone =2D From the newsgroup pipes up with a correction to my methodology. Jack. =2D --=20 Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash =2D----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAXtAfGPFSfAB/ezgRAgeFAJ4mwb8Xk5Z0QuPAD3FyooEvhc8t5gCgnEMx gqrpyBBX4Y0FzaR1VPcnAXI=3D =3D+myT =2D----END PGP SIGNATURE----- |
Your antenna is resonant a little BELOW 7.000 MHz.
Is that what you expect? W1MCE Jack Twilley wrote: -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 The weekend was beautiful, so I was able to do some outside work. I measured the antenna's impedance over 40m, then shortened the 40m legs by two feet each. I then measured the antenna's impedance again, and came up with numbers more closely resembling what I'd expect: Frequency Resistance Reactance Impedance 7.00 14 6 15.2 7.05 18 15 23.4 7.10 18 21 27.7 7.15 21 20 29.0 7.20 24 27 36.1 7.25 28 36 45.6 7.30 28 43 51.3 These measurements were done using a slightly different method. This time, I set the noise bridge for R=50 X=0 with the power off, then tuned the drive on my receiver for maximum noise before powering on the noise bridge and finding the null. The noise bridge manual is not as detailed as I would like, and it's not clear what the "proper" method is, but this produces reasonable results. The impedance is well within a 2:1 match throughout the voice segment, and a 3:1 match across the entire band. In other news, I happened to tune across 20m for the last five minutes of the Virginia QSO Party, and I made two contacts (NC4S and N4NW). I feel better about the performance of my antenna on that band, but I really hope that it's because the tuning somehow helped, and not that contesters are the only ones willing to dig into the noise. So it seems like I'm on the right track. I am going to try lengthening the antenna by six inches and doing another round of testing before moving on to the second set of legs, unless someone - From the newsgroup pipes up with a correction to my methodology. Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAXtAfGPFSfAB/ezgRAgeFAJ4mwb8Xk5Z0QuPAD3FyooEvhc8t5gCgnEMx gqrpyBBX4Y0FzaR1VPcnAXI= =+myT -----END PGP SIGNATURE----- |
Jack, Don't really see anything wrong with your methodology. I hope the 'fun' is in the 'getting there', 'cuz with more than one set of 'legs' on the antenna, you'll get to do the testing/tuning at least twice for each set, after doing each set. At least that's been my experience (never lucky enough to get it 'right' the first several times LOL!)... 'Doc |
It looks like if we extrapolate the reactance will go to zero below 7 MHz
and change sign. So it's still too long! 73 Hank WD5JFR "Jack Twilley" wrote in message ... -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 The weekend was beautiful, so I was able to do some outside work. I measured the antenna's impedance over 40m, then shortened the 40m legs by two feet each. I then measured the antenna's impedance again, and came up with numbers more closely resembling what I'd expect: Frequency Resistance Reactance Impedance 7.00 14 6 15.2 7.05 18 15 23.4 7.10 18 21 27.7 7.15 21 20 29.0 7.20 24 27 36.1 7.25 28 36 45.6 7.30 28 43 51.3 These measurements were done using a slightly different method. This time, I set the noise bridge for R=50 X=0 with the power off, then tuned the drive on my receiver for maximum noise before powering on the noise bridge and finding the null. The noise bridge manual is not as detailed as I would like, and it's not clear what the "proper" method is, but this produces reasonable results. The impedance is well within a 2:1 match throughout the voice segment, and a 3:1 match across the entire band. In other news, I happened to tune across 20m for the last five minutes of the Virginia QSO Party, and I made two contacts (NC4S and N4NW). I feel better about the performance of my antenna on that band, but I really hope that it's because the tuning somehow helped, and not that contesters are the only ones willing to dig into the noise. So it seems like I'm on the right track. I am going to try lengthening the antenna by six inches and doing another round of testing before moving on to the second set of legs, unless someone - From the newsgroup pipes up with a correction to my methodology. Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAXtAfGPFSfAB/ezgRAgeFAJ4mwb8Xk5Z0QuPAD3FyooEvhc8t5gCgnEMx gqrpyBBX4Y0FzaR1VPcnAXI= =+myT -----END PGP SIGNATURE----- |
Jack,
For what its worth, I ran EZNEC on a 40m dipole at 17 feet. I think you said yours was less than 20 feet up. For a flat top dipole, I got a resonant impedance of 23 Ohms. When I dropped the ends 15 degrees, the impedance dropped to 17 Ohms. Sort of in line with what you are getting. Also, with multiple dipoles the impedance will be less, because you can not completely ignore the other radiators. Maximum gain was in the straight up direction. Gain was about 6db down at 25 degrees elevation. On 15 meters, you have 4 lobes offset about 45 degrees from ends/broadside. Gain was about 3db down at 30 degrees elevation. Why don't you post your complete configuration. Height at feedpoint, and length and end point height for the three radiators. Tam/WB2TT "Jack Twilley" wrote in message ... -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 The weekend was beautiful, so I was able to do some outside work. I measured the antenna's impedance over 40m, then shortened the 40m legs by two feet each. I then measured the antenna's impedance again, and came up with numbers more closely resembling what I'd expect: Frequency Resistance Reactance Impedance 7.00 14 6 15.2 7.05 18 15 23.4 7.10 18 21 27.7 7.15 21 20 29.0 7.20 24 27 36.1 7.25 28 36 45.6 7.30 28 43 51.3 These measurements were done using a slightly different method. This time, I set the noise bridge for R=50 X=0 with the power off, then tuned the drive on my receiver for maximum noise before powering on the noise bridge and finding the null. The noise bridge manual is not as detailed as I would like, and it's not clear what the "proper" method is, but this produces reasonable results. The impedance is well within a 2:1 match throughout the voice segment, and a 3:1 match across the entire band. In other news, I happened to tune across 20m for the last five minutes of the Virginia QSO Party, and I made two contacts (NC4S and N4NW). I feel better about the performance of my antenna on that band, but I really hope that it's because the tuning somehow helped, and not that contesters are the only ones willing to dig into the noise. So it seems like I'm on the right track. I am going to try lengthening the antenna by six inches and doing another round of testing before moving on to the second set of legs, unless someone - From the newsgroup pipes up with a correction to my methodology. Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAXtAfGPFSfAB/ezgRAgeFAJ4mwb8Xk5Z0QuPAD3FyooEvhc8t5gCgnEMx gqrpyBBX4Y0FzaR1VPcnAXI= =+myT -----END PGP SIGNATURE----- |
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Hash: SHA1 "Dave" == Dave Shrader writes: Dave Your antenna is resonant a little BELOW 7.000 MHz. Is that what Dave you expect? Actually, my goal is for the antenna to be resonant at 7.150. If it's resonant too low, then I need to shorten the wires even more, right? Dave W1MCE Jack. (higher frequency is shorter wavelength) - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAX45wGPFSfAB/ezgRAo4lAKCgcj3oVMYNxuesHR+dWX/RijVd6ACfUY2a X/44ZVxZispMQOrqW0eGgcU= =RyMs -----END PGP SIGNATURE----- |
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Hash: SHA1 Unfortunately my wife doesn't have as much fun with that part as I do. Looks like I'm in for a month or so of iterations. Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAX46pGPFSfAB/ezgRAgVvAKC9qIfAYWT5+5ZXYwhYfK7rbBaDfACfXxKp mRbLo0U3ZcPGcDMcuDi+EB8= =LOnQ -----END PGP SIGNATURE----- |
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Hash: SHA1 "Tam" == t-tammaru Tam writes: Tam Jack, For what its worth, I ran EZNEC on a 40m dipole at 17 Tam feet. I think you said yours was less than 20 feet up. For a flat Tam top dipole, I got a resonant impedance of 23 Ohms. When I dropped Tam the ends 15 degrees, the impedance dropped to 17 Ohms. Sort of in Tam line with what you are getting. Also, with multiple dipoles the Tam impedance will be less, because you can not completely ignore the Tam other radiators. Maximum gain was in the straight up direction. Tam Gain was about 6db down at 25 degrees elevation. On 15 meters, Tam you have 4 lobes offset about 45 degrees from Tam ends/broadside. Gain was about 3db down at 30 degrees elevation. That doesn't look so bad at all. Tam Why don't you post your complete configuration. Height at Tam feedpoint, and length and end point height for the three Tam radiators. Over the next couple of days, I'll take some careful measurements of the antenna, its supports, and the distance of everything from the back of the house. The house was built in the 1940s and was constructed with wood and concrete with a stucco finish. Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAX4+LGPFSfAB/ezgRAtjlAJ4wxt16eFbsHlxu+C7OvsfHqoX4MwCg+UEd NkhKArjbg1fF1h2YeURz7Sc= =bKgV -----END PGP SIGNATURE----- |
On Mon, 22 Mar 2004 17:10:02 -0800, Jack Twilley
wrote: Actually, my goal is for the antenna to be resonant at 7.150. If it's resonant too low, then I need to shorten the wires even more, right? Hi Jack, Resonance is not all that it is cracked up to be. Be careful of seeking something that yields little return on your effort. For instance, the numbers you've offered show a very low Z for that anticipated goal. This means you will still need to transform that value to reduce SWR, which in its own pursuit is an equally low yield return. You will need a tuner any way you look at it, and the higher R values at the higher frequencies are probably more due in part to the loss of nearby ground, rather than the miracle of a neighboring resonance. My guess is that you have already obtained an optimal situation = it don't get any better than this even with all the trimming you may accomplish. Worse, you could double its height and contacts may never notice the improvement in "efficiency." Basically all your work is to achieve bragging rights, and you could cheat and start bragging right now to no one's challenge. 73's Richard Clark, KB7QHC |
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Hash: SHA1 "Richard" == Richard Clark writes: Jack Actually, my goal is for the antenna to be resonant at 7.150. Jack If it's resonant too low, then I need to shorten the wires even Jack more, right? Richard Hi Jack, Richard Resonance is not all that it is cracked up to be. Be careful Richard of seeking something that yields little return on your Richard effort. This is a very good point. Richard For instance, the numbers you've offered show a very low Z Richard for that anticipated goal. This means you will still need to Richard transform that value to reduce SWR, which in its own pursuit Richard is an equally low yield return. Yes, but pursuing a match close to 1:1 and an impedance close to 50 ohms seems to be a reasonable pursuit, if I understand correctly. Richard You will need a tuner any way you look at it, and the higher Richard R values at the higher frequencies are probably more due in Richard part to the loss of nearby ground, rather than the miracle of Richard a neighboring resonance. Possibly. I hope a accurate description of my antenna's geometry and surrounding structures will assist in resolving this question. Richard My guess is that you have already obtained an optimal Richard situation = it don't get any better than this even with all Richard the trimming you may accomplish. Worse, you could double its Richard height and contacts may never notice the improvement in Richard "efficiency." Basically all your work is to achieve bragging Richard rights, and you could cheat and start bragging right now to Richard no one's challenge. That's a reasonable guess. However, I think I've got a bit more experimenting to do before I can reach that conclusion. I disagree with the assertion that "bragging rights" is the goal here, though. I don't see any point in bragging -- there's nothing terribly unusual or special about what I'm doing. I'm not going after DXCC with a magnetic loop the size of a ream of paper, or WAS from a radio in an Altoids can. I'm just trying to have the best antenna my environment and budget can support. Richard 73's Richard Clark, KB7QHC Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAX/V8GPFSfAB/ezgRAt50AKCq7zoLl5a5QFvJXYhAqDDvynP32QCbBm+I inV/OPyW2pLenSTK/jppimE= =m5xy -----END PGP SIGNATURE----- |
YEP!!
Jack Twilley wrote: Actually, my goal is for the antenna to be resonant at 7.150. If it's resonant too low, then I need to shorten the wires even more, right? |
On Tue, 23 Mar 2004 00:29:43 -0800, Jack Twilley
wrote: Yes, but pursuing a match close to 1:1 and an impedance close to 50 ohms seems to be a reasonable pursuit, if I understand correctly. Hi Jack, This is an aspiration on par with monks seeking nirvana. The two illustrate it is the path, not the destination that is meaningful. There is a very clear point to be made that unless you elevate the dipole, any 50 Ohm characteristic you observe will more ground loss than radiation resistance. This is reasonable only in the sense of ease of tuning and the reductio ad absurdum is bliss can be found in a dummy load. Clipping the ends of the current structure do not lead to increased benefit unless you shave your advantage in tenths of a dB. To put that in perspective, unless you are a teenager, you and your contacts couldn't possible hear any change below 1dB variation. To force that perspective further, propagation variation through one QSO easily varies by that much or more (unless we are talking line of sight FM with full quieting). 73's Richard Clark, KB7QHC |
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Hash: SHA1 "Richard" == Richard Clark writes: Richard On Tue, 23 Mar 2004 00:29:43 -0800, Jack Twilley Richard wrote: Yes, but pursuing a match close to 1:1 and an impedance close to 50 ohms seems to be a reasonable pursuit, if I understand correctly. Richard Hi Jack, Richard This is an aspiration on par with monks seeking nirvana. The Richard two illustrate it is the path, not the destination that is Richard meaningful. Richard There is a very clear point to be made that unless you Richard elevate the dipole, any 50 Ohm characteristic you observe Richard will more ground loss than radiation resistance. This is Richard reasonable only in the sense of ease of tuning and the Richard reductio ad absurdum is bliss can be found in a dummy load. Oh, I see your point here. What you're saying is that my dipole is so far from the ideal that reaching 50 ohms won't mean anywhere near the same thing that it does to the ideal case. That begs the question, then -- if not 50 ohms, what is the best value for my particular configuration? Richard Clipping the ends of the current structure do not lead to Richard increased benefit unless you shave your advantage in tenths Richard of a dB. To put that in perspective, unless you are a Richard teenager, you and your contacts couldn't possible hear any Richard change below 1dB variation. To force that perspective Richard further, propagation variation through one QSO easily varies Richard by that much or more (unless we are talking line of sight FM Richard with full quieting). I've listened to QSOs where they've ebbed down to the noise floor and flooded back several times over the course of a minute, so I understand what you're saying. Richard 73's Richard Clark, KB7QHC I am really interested in knowing what sort of target values would represent an optimal configuration, if that's at all possible. Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAYK1zGPFSfAB/ezgRArdhAKDfNKIpcmwQvZaJjulkOrwc4sGK+wCfVlap TxvN060RLyzIZD4+YO6MXrc= =Kg/a -----END PGP SIGNATURE----- |
On Tue, 23 Mar 2004 13:34:38 -0800, Jack Twilley
wrote: Oh, I see your point here. What you're saying is that my dipole is so far from the ideal that reaching 50 ohms won't mean anywhere near the same thing that it does to the ideal case. That begs the question, then -- if not 50 ohms, what is the best value for my particular configuration? I am really interested in knowing what sort of target values would represent an optimal configuration, if that's at all possible. Jack. Hi Jack, For the height you are at, you are probably already at the optimal solution. If you could optimize further, at this height, it would barely eke out 1dB difference. Ground dominates your design. This is a heresy with dipole aficionados, but building a ground screen will help toward the quickest, easiest 1dB return. You don't have to do anything but shallow bury copper for the length of dipole + 20% and maybe a quarter wavelength wide, beneath it. It need not attach to anything to be beneficial. A grid of wires, 1M on a side is a good first step. You will undoubtedly note a tuning change, use a tuner to adjust (you need it anyway). Some may distract you pointing out that it simply sends more signal up. True, but as a screen, it removes loss, and allows more signal out toward the horizon too. 73's Richard Clark, KB7QHC |
Jack Twilley wrote:
. . . Frequency Resistance Reactance Impedance 7.00 14 6 15.2 7.05 18 15 23.4 7.10 18 21 27.7 7.15 21 20 29.0 7.20 24 27 36.1 7.25 28 36 45.6 7.30 28 43 51.3 . . . The impedance is well within a 2:1 match throughout the voice segment, and a 3:1 match across the entire band. Assuming a 50 ohm system, the SWR for each of your impedances is shown in the SWR column below. You might want to review how SWR is calculated -- the ARRL Antenna Book is a good source. Frequency Resistance Reactance Impedance SWR 7.00 14 6 15.2 3.63 7.05 18 15 23.4 3.06 7.10 18 21 27.7 3.33 7.15 21 20 29.0 2.83 7.20 24 27 36.1 2.82 7.25 28 36 45.6 2.93 7.30 28 43 51.3 3.37 Roy Lewallen, W7EL |
"Jack Twilley" wrote in message ... -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 "Richard" == Richard Clark writes: Richard On Tue, 23 Mar 2004 00:29:43 -0800, Jack Twilley Richard wrote: Yes, but pursuing a match close to 1:1 and an impedance close to 50 ohms seems to be a reasonable pursuit, if I understand correctly. Richard Hi Jack, Richard This is an aspiration on par with monks seeking nirvana. The Richard two illustrate it is the path, not the destination that is Richard meaningful. Richard There is a very clear point to be made that unless you Richard elevate the dipole, any 50 Ohm characteristic you observe Richard will more ground loss than radiation resistance. This is Richard reasonable only in the sense of ease of tuning and the Richard reductio ad absurdum is bliss can be found in a dummy load. Oh, I see your point here. What you're saying is that my dipole is so far from the ideal that reaching 50 ohms won't mean anywhere near the same thing that it does to the ideal case. That begs the question, then -- if not 50 ohms, what is the best value for my particular configuration? .................................................. ........................... .................... Jack, You may have a misconception about impedance here. Making the antenna resonant is not going to make it 50 Ohms. Extrapolating your numbers, it looks like resonance would be at around 6.9 MHz, and give you an impedance of something like 12 + j0. Might be a good match to a 1:4 (not 4:1) balun, but you would have to see what happens on the other bands. Tam/WB2TT |
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Hash: SHA1 "Jack" == Jack Twilley writes: Jack Over the next couple of days, I'll take some careful Jack measurements of the antenna, its supports, and the distance of Jack everything from the back of the house. The house was built in Jack the 1940s and was constructed with wood and concrete with a Jack stucco finish. http://www.twilley.org/~jmt/antenna/dipole.html The only thing I'm missing because I didn't think to measure it was how long the individual dipole legs are. However, they started off as the normal lengths for a full-length 40m dipole and inverted vees for 20m and 10m, as mentioned in the page. Tomorrow I'll go out and measure the wires and update the text and the relevant drawing with that information. Tam, if you do model this antenna, I'd really appreciate it if you shared the model with me as I've always wanted to learn more about nec4 and friends but never really had the ability to get past the punch-card mindset of the input files, and having my own antenna modeled would probably do it. Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAYSmrGPFSfAB/ezgRArsoAKDwJjajxoQ8flxBLEZvJX7k8WgXpgCgtMZl o4pYEPDM06R9qsu00CQPo40= =TUkE -----END PGP SIGNATURE----- |
En Tam/WB2TT va escriure en Tue, 23 Mar 2004 20:08:18 -0500:
Jack, You may have a misconception about impedance here. Making the antenna resonant is not going to make it 50 Ohms. Extrapolating your numbers, it looks like resonance would be at around 6.9 MHz, and give you an impedance of something like 12 + j0. Might be a good match to a 1:4 (not 4:1) balun, but you would have to see what happens on the other bands. Tam/WB2TT Just a silly thought: If he made it resonant and had, indeed, 12 ohms, couldn't he make it into a folded dipole giving 12x4=48 ohms and probably a better bandwidth? (Of course this is assuming monoband operation) EA3FYA - Toni |
En Toni va escriure en Wed, 24 Mar 2004 08:15:16 +0100:
En Tam/WB2TT va escriure en Tue, 23 Mar 2004 20:08:18 -0500: Jack, You may have a misconception about impedance here. Making the antenna resonant is not going to make it 50 Ohms. Extrapolating your numbers, it looks like resonance would be at around 6.9 MHz, and give you an impedance of something like 12 + j0. Might be a good match to a 1:4 (not 4:1) balun, but you would have to see what happens on the other bands. Tam/WB2TT Just a silly thought: If he made it resonant and had, indeed, 12 ohms, couldn't he make it into a folded dipole giving 12x4=48 ohms and probably a better bandwidth? (Of course this is assuming monoband operation) EA3FYA - Toni Oops, Just read in a previous post he is using a fan dipole. Don't think it is possible to use the folded dipole then. EA3FYA - Toni |
"Toni" wrote in message ... En Toni va escriure en Wed, 24 Mar 2004 08:15:16 +0100: En Tam/WB2TT va escriure en Tue, 23 Mar 2004 20:08:18 -0500: Jack, You may have a misconception about impedance here. Making the antenna resonant is not going to make it 50 Ohms. Extrapolating your numbers, it looks like resonance would be at around 6.9 MHz, and give you an impedance of something like 12 + j0. Might be a good match to a 1:4 (not 4:1) balun, but you would have to see what happens on the other bands. Tam/WB2TT Just a silly thought: If he made it resonant and had, indeed, 12 ohms, couldn't he make it into a folded dipole giving 12x4=48 ohms and probably a better bandwidth? (Of course this is assuming monoband operation) EA3FYA - Toni Oops, Just read in a previous post he is using a fan dipole. Don't think it is possible to use the folded dipole then. EA3FYA - Toni Toni, I think you are right. Seems like the 40m folded dipole should be a short circuit at 20. For a single dipole though, what you say makes sense (to me). Tam/WB2TT |
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