On Sat, 8 Sep 2001 K7GCO@aol.com writes:
>
SNIP
>>
> This 12/10M interference is a puzzling concept. In all the 5 band 2
> element tune ups I've done in Eznec I've been able to get clean
> patterns adjusting the reflectors on every band. So has the W6
> that had a 2 element 5 band quad in QST.
> If 12M affects 10M, why doesn't 15M affect 12M, 17M affect 15M
> and 20M affect 17M? Or the reverse?
SNIP
> K7GCO
The reason that 12M parasitic elements interact with
other bands more than any other combination becomes
when you compare the % difference between bands.
28 / 24.9 = 1.1245 for a 12.45% difference
24.9 / 21.45 = 1.16 for a 16% difference
21 / 18.1 = 1.16 for a 16% difference
18.1 / 14.35 = 1.25 for a 25% difference
It is clear that on a percentage basis, 10 and 12 Meters
are closest in size.
Remembering that typical reflectors are 2 to 6% longer than
self resonant elements and typical directors are 2 to 6%
shorter than self resonant elements, we see that a 10M
reflector is nearly identical in size to a 12M director.
As we go lower in frequency, the differences are greater
and the interactions become less significant.
This analysis applies to Yagi antennas as well as to
Quad antennas.
Tom N4KG
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