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RSGB RadCom December 2007 Issue
"Roy Lewallen" wrote in message ... Mike Kaliski wrote: Those that can get access to a copy should look at the Radio Society of Great Britain, RadCom Magazine, December 2007 issue, Technical Topics column by Pat Hawker G3VA. The topic? 50 Years of amateur antennas. He covers a lot of the perennial topics of debate in this newsgroup and provides some excellent commentary on element lengths, feedline lengths, SWR, ATU's, modes of operation and some of the controversy. Okay, it has probably all been covered elsewhere in books, on websites and in this newsgroup, but there is a lot of useful information condensed into a couple of pages. Almost a substitute fro Kraus and Terman! :-) Mike G0ULI Does he cover the radiation of antennas from 377 ohm "sweet spots", and the concept of using antennas to match free space's impedance? Roy Lewallen, W7EL Hi Roy, He does mention that antennas possess radiation resistance, not to be confused with and not the same as, characteristic impedence (or feedpoint impedence) and that the characteristic impedence will vary along an antennas length. As for the actual point(s) along an element at which an antenna radiates (transfers energy to free space) with maximum efficiency, he makes no comment. I seriously doubt that there is anything in the article that you would dispute. It seems that everyone was so busy laughing on this newsgroup, that no one has actually provided any information as to whether any detailed research has ever been carried out as to what is going on within the radiating elements of an antenna. There is loads of theory in the text books, but I have yet to see any empirical measurements or results. I am aware of the research into small loops carried out by Professor Underhill (also published in RadCom) but it seems that even his results have been disputed. I may have submitted the post, tongue in cheek, to stir things up a bit, but on reflection there seems to be something of merit in the idea. I am revisiting the appropriate chapters in Kraus and Terman to see where the error in my logic is. In the absence of any direct evidence of contradiction, I think it may be worth developing this idea and making a few measurements of my own to see what the truth of the matter is. Amateur radio is supposed to be a learning experience, right? And you can't learn without making mistakes. After 40 years of following the diktats of professional communications and electronic theory, I think the time is right to kick off the traces and challenge some of the accepted authodoxies. I do know all the conventional stuff, it just doesn't satisfy my soul. You probably know more about antennas than anyone has a right to know Roy, but it's a strange universe out there and it's just possible that there's a few more things to learn yet. Regards Mike G0ULI |
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