Is the 4x4 pressure treated? Or from a local sawmill and uncured?
Both will have an effect.
Carl
KM1H
----- Original Message -----
From: "Glenn Biggerstaff" <ww4b73@gmail.com>
To: <topband@contesting.com>
Sent: Monday, January 07, 2013 9:30 PM
Subject: Topband: A 160 Meter antenne puzzle
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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