I appreciate Jon's comments below. As he pointed out, my interest in
LPDA's is due to my MARS work.
Jon, if you get a chance, read September 2002 QST, pp31!
>Practical High Performance HF Log Periodic Antennas
>Keywords: CONSTRUCTION DESIGN ANTENNA BEAM LOG
>PERIODIC HF 10 METER 12 METER 15 METER 17 METER 20 METER
>30 METER
>By Bill Jones, K8CU
(also found here...http://www.realhamradio.com/Log_Periodic.htm)
I learned more about LPDA's from this article than anything I've read to
date! I will have to re-read the article myself, but I remember talk about
front-to-back figures that were BETTER than a small yagi. You can also
check out Paul Sergi's stacked array at...
http://www.dxengineering.com/
I believe that LPDA's are sorely underated! Sure they are a
compromise...but isn't everything?...traps vs open air loading...etc. I'm
not saying they are for everyone...they're not! But they deserve a look!
Jon said:
>While an LPDA is a great antenna (I worked for Dr. Paul Mayes who was one of
>the inventors of the beast), I do question it's usefulness in the amateur
>world at HF.
>
>An LPDA has less gain than a Yagi and while it has significantly broader
>bandwidth, there's a lot of bandwidth covered that isn't particularly
>necessary to the ham. As you pointed out those who also work in the MARS
>bands will certainly find one more useful than a Yagi.
>
>I know some beams like the CC X7 use an LPDA type arrangement for the driven
>elements and that probably does help beamwidth.
>
>But in an LPDA overall, most of the elements are not active at your
>frequency of use.
>
>I really don't know what one can get out of an LPDA that you cannot get out
>of a well designed multi-band Yagi.
>
>I'd love to be enlightened.
>
>73,
>Jon
>NA9D
Dino...k6rix@arrl.net
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