Thanks Warren, I think you shed really the light on the topic. Also it is consistent with the ARRL Antenna book. A 49:1 transformer can work efficiently only on some specific points, otherwise either you see a very high SWR, or you don't see that high SWR because the 'SWR transforms into heat'. It's 'an accounting principle, or a if you prefer a principle of conservation'... If you use a 49:1 transformer and you find that at 1/4 lambda the SWR is not close to 100, than you risk to melt the transformer. The efficency on random frequencies cannot be much more than just a wire connected to the 50 ohm antenna output of the radio. The only difference is that you see the high SWR in the latter case.
Il 31/lug/2018 12:38, "Warren Allgyer" <
allgyer@...> ha scritto:
I have returned home from vacation and now have better access to some of my files.
In March of this year I had an extensive email exchange with Bob Allison, WB1GCM and Joel Hallas, W1ZR, the authors of the 2016 review of the MyAntennas EFHW. I have supplied that full email exchange to Jerry and Allison but I have chosen not to post it here because of its size.
In that exchange however were some data files that I would like to share with the group. These document the transformer losses in this system when properly terminated in a resistive load. In actual operation these losses would be the best case and would be experienced only when the antenna is a resonant multiple of a half wave. The losses when not terminated in a 2470 ohm resistive load, which would be the case if the antenna were used on any band other than the single resonant band, are far higher. On the order of 8 - 10 dB.
I would be happy to send the entire email trail to anyone who wishes to see it by private email. In it the test methodology for the article, which I found lacking, are discussed extensively along with my own tests.
WA8TOD
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