At 01:23 PM 2006-12-20, Joe Subich, W4TV wrote:
> > On the other hand, as K4SAV describes, the array of verticals has
> > a null at zenith, which could help attenuate lightning static and
> > NVIS QRM.
>The K9AY can be "fixed" if you are willing to use additional supports
>to make the loop square. The high angle response is due to the sloping
>"verticals." However, given the performance of the whip 4-squares, the
>effort is not justified.
All the models I have of a K9AY (either delta or rectangle/square),
EWE, and Flag have response at the zenith due to the current flowing
in the horizontal wires (or the horizontal component of the current
in the delta versions). I don't see any way to put a null straight
up with these designs. It's always about 5 dB down from the peak
signal. Do you have a model you can share that has a null at the zenith?
> > Incidentally, models of the DX Engineering array actually show
> > slightly better RDF (a few tenths of a dB) at closer spacings than
> > 1/4 wl (with appropriate phasing). I suspect the arrays of EWEs and
> > K9AYs would be similar.
>Yes, closer spacing produces better RDF for the K9AY and EQE arrays.
>However, the closer spacing comes at a big cost in signal levels on
>the lowest band - overall "gain" can be as little as -35 dBi which
>then requires a rather stout, low noise, low IMD preamplifier or the
>benefits of the array are lost in the IMD and preamplifier noise.
A good point. There are always compromises to deal with when you
attempt wideband designs.
73, Terry N6RY
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