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Just playing devels advocate here, but, as you state "If you put X watts
into one antenna and extract Y watts from an antenna coupled to it, and measure the efficiency of the "transformer" the same way as you did the conventional transformer, you'll find it has lousy efficiency.", does that refer to the 377 ohms (or so) free space coupling impedence, or could that effeciency be improved by having the antenna's matched radiation resistance approach that 377 ohms? (I.E. max transfer of power is at Z0 (in) matches Z0(out)! or, is this academic for this? Perhaps, better for Dr. Shorza Gitchigoumi of CQ fame, or Larson E. Rapp of ARRL fame (both with bad habit of only presenting articles in the 4th month of the year in their respective publications) ! But, I'd thought I had better ask! Jim NN7K "Roy Lewallen" wrote in message ... I hope you'll pardon me for amplifying this a little. If you put X watts into the primary of a transformer and extract Y watts from the secondary, the efficiency is Y/X by definition. If you put X watts into one antenna and extract Y watts from an antenna coupled to it, and measure the efficiency of the "transformer" the same way as you did the conventional transformer, you'll find it has lousy efficiency. Why? Because a goodly fraction of the power you applied to the "primary" antenna never gets to the "secondary" antenna because it's radiated instead. As far as the "secondary" is concerned, it might as well have been converted to heat. If you look at the impedance of the "primary" antenna, you'll find an excess of resistance -- just enough, in fact, to account for the "lost" (radiated) power. This isn't a statement about how well coupled antennas function as antennas, whose purpose is to radiate after all. It's a statement about how well they function as a transformer. Poorly. Roy Lewallen, W7EL |
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#3
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'corse, should have attached the "smiley face" (my cynisicasm is/was on
:) !! ) Jim "Roy Lewallen" wrote in message ... The answer is no. You should be able to figure out the reason why by reading the previous postings in this thread. Roy Lewallen, W7EL wrote: Just playing devels advocate here, but, as you state "If you put X watts into one antenna and extract Y watts from an antenna coupled to it, and measure the efficiency of the "transformer" the same way as you did the conventional transformer, you'll find it has lousy efficiency.", does that refer to the 377 ohms (or so) free space coupling impedence, or could that effeciency be improved by having the antenna's matched radiation resistance approach that 377 ohms? (I.E. max transfer of power is at Z0 (in) matches Z0(out)! or, is this academic for this? Perhaps, better for Dr. Shorza Gitchigoumi of CQ fame, or Larson E. Rapp of ARRL fame (both with bad habit of only presenting articles in the 4th month of the year in their respective publications) ! But, I'd thought I had better ask! Jim NN7K "Roy Lewallen" wrote in message ... I hope you'll pardon me for amplifying this a little. If you put X watts into the primary of a transformer and extract Y watts from the secondary, the efficiency is Y/X by definition. If you put X watts into one antenna and extract Y watts from an antenna coupled to it, and measure the efficiency of the "transformer" the same way as you did the conventional transformer, you'll find it has lousy efficiency. Why? Because a goodly fraction of the power you applied to the "primary" antenna never gets to the "secondary" antenna because it's radiated instead. As far as the "secondary" is concerned, it might as well have been converted to heat. If you look at the impedance of the "primary" antenna, you'll find an excess of resistance -- just enough, in fact, to account for the "lost" (radiated) power. This isn't a statement about how well coupled antennas function as antennas, whose purpose is to radiate after all. It's a statement about how well they function as a transformer. Poorly. Roy Lewallen, W7EL |
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