Hi,
Is it really necessary to isolate the vertical from the pressure treated 4 x
4 with PVC tubing and is it really necessary to install a 1:1 balun between
the antenna and feedline in this 4-square receiving array?
Doug
"Think of all the ways you can hurt yourself laughing."
-----Original Message-----
Hi everybody and happy new year .
I have what I think is an interesting antenna riddle . I have some receive
antenna verticals (4) that are selected by relays in pair and the pair is
fed back to the shack to a phasing boxing .Each antenna is AL tubing about
30 feet tall, base loaded with an inductor and a resistor very much like
ON4UN has for his 4 square receive array .There is a 1 to 1 balun between
the antenna and the feed line . The tubing is insulated with an eight inch
length of pvc pipe from the 4x4 that supports it .The overlap between the
tubing and the 4x4 is about eight inches as well . I was doing some testing
today and discovered that touching the 4x4 at the top caused the swr to
increase from about 1.2 to 1 to 1.7 to 1 . The lower on the 4x4 I touch the
less the effect . I am only moving my finger a fraction of an inch and my
hand not at all when this happens .The feed lines are disconnected when this
is going on .There is no dc continuity between the antenna and any mounting
hardware or th
e post .I disconnected the base loading and put the analyzer on it and it
is resonant at about 8 mhz and touching the post causes no change with this
setup . There are eight 30 foot radials laying on the ground and a 2 inch
wide copper strap about 3 foot long in the hole that the 4x4 is in .
What is going on here and should I make an effort to limit the coupling
between the 4x4 and the antenna?
73 , Glenn WW4B
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Topband Reflector
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