he old "rule of thumb" based on boom lengths wasn't calculated.
It was a number pulled out of the air...
Remember that significantly smaller elements are not
seen by larger elements (i.e. a 20M beam is essentially
unaffected by a 10M beam) but the 10M beam IS affected
by a 20M (or 15M ) beam.
Element spacings on multi-element Yagi's are typically
between 0.1 and 0.25 WL so to prevent coupling to other
antennas, the spacing should be greater than the maximum
element spacing on the higher frequency antennas. That
means that a 10M beam should be 8 or more feet away from
lower band antennas.
Of course if you want to know more precisely, MODEL IT.
Tom N4KG
On Fri, 3 Aug 2001 "Geo - W7LFD" <gclute@home.com> writes:
>
> I just found an old Assembly Instructions publication from CushCraft
> on my 4
> element 10 meter beam...model no. A28-4. It says as a general rule
> "When
> stacking dissimiliar beams on the same mast use a spacing equal to
> half the
> boom length of the longest antenna. In no case should the spacing
> be less
> than 6 foot.
>
> No explanation as to how this was calculated.
>
> George W7LFD
>
>
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> systems,
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