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#1
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Reg Edwards wrote:
In view of the nil replies to the following posting it's safe to say that's another old wives' tale which bites the dust. Reg, we have a clear example of where the high voltage part of the antenna is not allowed to radiate (much). That would be a balanced top hat. Not allowing the high voltage part of the antenna to radiate leaves the high current part to do most of the radiating. We know from field strength measurements that a mobile antenna with a balanced top hat can radiate as well (or better than) an antenna equipped with a radiating high voltage top section. If you keep the high voltage portion of the antenna and replace the high current portion with an antenna tuner, the field strength falls by some 12 dB. Lengthening the high current section under the loading coil has a much greater effect than lengthening the high-voltage section on top of the loading coil. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#2
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Cec, I don't doubt your experimental results. It's your extrapolated
imagination and logic which worries me. ;o) ---- Yours, Reg. |
#3
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Reg Edwards wrote:
Cec, I don't doubt your experimental results. It's your extrapolated imagination and logic which worries me. ;o) I didn't imagine those experimental results, Reg, and all I did was report those results. My logic tells me that there is a grain of valid circumstantial evidence in there somewhere. What you need to do to prove your point is present an antenna where the high-current portion is prohibited from radiating yet still yields a high field strength. Example #1: The top half of an electrical 1/4WL antenna is prohibited from radiating by a balanced top hat. Field strength results are similar to a 1/4WL monopole. This has already been presented. Example #2: The bottom half of an electrical 1/4WL antenna is prohibited from radiating by _________________. Fill in the blank and prove that field strength results are similar to a 1/4WL monopole. That's all you need to do to make a believer (instead of a doubter) out of me. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#4
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Its the voltage parts of the antenna which do the radiating.
That is proved by cutting off the top part of the antenna and replacing it with a top hat which has a much larger capacitance so it radiates the power harder. --- Reg. |
#5
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Reg Edwards wrote:
Its the voltage parts of the antenna which do the radiating. That is proved by cutting off the top part of the antenna and replacing it with a top hat which has a much larger capacitance so it radiates the power harder. Reg, let's say we have an elevated antenna system where the radial system and top hat system are identical and balanced. Energy flows back and forth between the radials and top hat. Very little energy is radiated from either the top hat or the radials since they are balanced. Virtually all of the radiated energy comes from the high-current vertical portion of the antenna. Such antennas are described in Appendix II - Short Ground-Mounted Verticals in _Building_and_Using_Baluns_and_Ununs_ by Jerry Sevick, w2fmi. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#6
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Cec, who's Jerry Sevick. I don't seem to have a copy of his works around me
at present. --- Reg. |
#7
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Reg Edwards wrote:
Cec, who's Jerry Sevick. I don't seem to have a copy of his works around me at present. He's accepted by most as *the* ham balun guru. Some disagree. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#8
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Cecil Moore wrote: Reg, we have a clear example of where the high voltage part of the antenna is not allowed to radiate (much). That would be a balanced top hat. Not allowing the high voltage part of the antenna to radiate leaves the high current part to do most of the radiating. Cecil, Reg makes a good point. We know that the same amplitude (less ohmic losses) of current travels the entire length of the antenna in both directions. The relative phase of forward and reverse currents simply makes the superposition of the two currents greater at one end than another. We might measure the standing wave current with an ammeter, but it is the traveling wave currents which radiate. 73, Jim AC6XG |
#9
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Jim Kelley wrote:
Reg makes a good point. We know that the same amplitude (less ohmic losses) of current travels the entire length of the antenna in both directions. The relative phase of forward and reverse currents simply makes the superposition of the two currents greater at one end than another. We might measure the standing wave current with an ammeter, but it is the traveling wave currents which radiate. A balanced top hat doesn't radiate much because the currents in the opposing elements are 180 degrees out of phase with each other. It doesn't matter if they are traveling waves or standing waves. If they are 180 degrees out of phase with each other, they are more like a transmission line than they are like an antenna. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#10
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Cecil Moore wrote:
Reg, we have a clear example of where the high voltage part of the antenna is not allowed to radiate (much). That would be a balanced top hat. Not allowing the high voltage part of the antenna to radiate leaves the high current part to do most of the radiating. Cecil, Reg makes a good point. We know that the same amplitude (less ohmic losses) of current travels the entire length of the antenna in both directions. The relative phase of forward and reverse currents simply makes the superposition of the two currents greater at one end than another. We might measure the standing wave current with an ammeter, but it is the traveling wave currents which radiate. 73, Jim AC6XG ============================ Jim, are you one of the crackpots who think that it's the voltage parts of the antenna which do the radiating which is proved by replacing the top portion of the antenna with a top hat which has a large capacitance so that the voltage has a greater effect. ;o) --- Reg, G4FGQ |