Thanks Frank and Uli, Today I was able to remove the insulation of the
quad driven element wire(s) and test the results. Zounds! Amazing change
as everything came back to normal. The Three element Cubex Quad is now
broadbanded ( as when I first installed it with #14 bare before i made
the mistake of restringing it with #16 covered solid) with the 1:1
bottom at 14.150 rather than at the lower band edge. You guys were spot
on with you observation. It is strange that I have never in all these
years seen any reference to this quad building although I have seen this
effect mentioned with 160 meter BOG radials. Now I guess I will wait for
a long boom bucket truck as stripping the insulation of the outside
elements would normally require taking this monster down. I have thought
of every possible way to do this by not having the expense of taking
everything down and/or a boom truck with a 80 foot reach and spinning
the outer elements as the tower climber (my son) spins the boom and I
strip the wire. My neighbor even suggested using a propane torch on the
end of a pole but that doesn't seem reasonable. Shortening the wires was
not an option because they are all strung on pre-set holes in the
fiberglass. Perhaps a 3% long reflector loop and director loop might not
cause a pattern reversal, which appear to be the case from all the
preliminary tests. But i still eventually want to get things correct.
73, Herb, KV4FZ
On 7/26/2013 8:13 PM, donovanf@starpower.net wrote: > Hi Herb, > >
Dielectric loading causes insulated wire to have a lower velocity factor
than bare wire. > The velocity factor of your particular wire can be
determined experimentally. > > This is exactly the same as the
dielectric loading that occurs when ice covers > our quads and Yagis (I
sure you're forgotten about that in the Virgin Islands!) . > Ice
increases the VSWR and in extreme cases reverses the directivity of a
Yagi. > This is exactly the same as what you're experiencing with
insulated wire. > > All of the loops (reflectors, driven elements,
directors) in your quad are now resonant > at a significantly lower
frequency than intended. As far as I know, the only was to > solve your
problem is to shorten all of the wires or replace them with bare wires.
73 Frank W3LPL
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Topband Reflector
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