[TowerTalk] Quad Element Tuning
Sat, 8 Sep 2001 19:01:15 -0600
On Sat, 8 Sep 2001 K7GCO@aol.com writes:
> 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?
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
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