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Efficiency of 200-ohm hairpin matching
Howdy gents,
I thought that the problem of the hairpin or Beta Match was kicked around way back, please see http://www.k3bu.us/beta_match.htm Hairpin is shortening the (most important) radiating part of the driven element where the current is the highest. The best way to match the long antennas with low feedpoint at the driven element is to use the folded dipole or Quad element, as I used in my Razor Beams http://www.k3bu.us/razor_beams.htm First you shorten the driven element, reduce the effective length, then you apply lossy matching and then you see less gain and narrower bandwidth. Folded dipole or quad elements fix that. Yuri, K3BU.us "Antonio Vernucci" wrote in message ... What you're probably seeing is a numerical problem in the NEC calculating engine. It's very fussy about the region near a source, and doesn't like small loops which include a source. You should run an Average Gain check (see "Average Gain" in the EZNEC manual index), which will reveal whether this is the problem. The double precision calculating engine in EZNEC+ is considerably more tolerant of small loops, but can still have problems with average gain for other reasons. Roy Lewallen, W7EL Hi Roy, thanks for the tip. As a matter of fact without the hairpin the average gain is almost zero, whilst with the hairpin is about -0.8 dB, that correponds to the gain drop I notice. So the problem you had anticipated actually occurs. I then tried to simulate the hairpin with a proper-length shorted trasmission line and, doing so, the average gain is almost 0. Evidently the program does not like the short hairpin loop. 73 Tony I0JX |
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