I concur with VE4XT's assessments that the open wire feedline is
probably the RFI culprit, and that the vertical's performance is
likely to be inferior to your dipole at 60'. Also, verticals
near a house are known RFI-generators because max radiation is
right down where the house wiring is located, and vertical
radiation is always looking for that missing half of the antenna,
causing more FRI in your house wiring.
I suggest converting your dipole to a fan dipole for 40/75, or
separate dipoles for 40/75, or even a trap dipole for 40/75,
feeding it/them with coax and a suitable K9YC choke(s) at the
feedpoint. Separate dipoles would be best, then a fan dipole,
then a trap.
I would try it on 75 with coax and a choke first to see if the
RFI problem goes away. If so, then start working on something
for 40.
Dave Hachadorian, K6LL
Yuma, AZ
-----Original Message-----
From: ve4xt@mymts.net
Sent: Wednesday, November 20, 2013 7:20 AM
To: Jim in Waco wb5oxq
Cc: TowerTalk@contesting.com
Subject: Re: [TowerTalk] Limited space for 80 and 50
It would be a shame to not be able to use this dipole, since your
vertical antenna won't come close to it without a lot of radials.
I suspect the problem isn't the antenna but rather the feedline.
I suspect the interference is a combination of feedline radiation
and the Pin 1 problem on your entertainment gear. Even some
so-called high-end consumer electronics suffer from poor
engineering.
Have you read any of K9YC's information on chokes and RFI (incl.
Pin 1)?
73, Kelly
ve4xt
Sent from my iPhone
On Nov 19, 2013, at 21:57, "Jim in Waco wb5oxq"
<wb5oxq_1@grandecom.net> wrote:
I have a full size 80 meter dipole at 60' in the center fed
with 300 ohm window line to a good tuner with the balanced
input. I cannot use it on 80 or 40 meters even at levels of 25
watts or more because of interfearance to my entertainment
center despite snap on chokes on all input leads and every
speaker lead and a high end ac line filter. Therefore if I
want to operate any frequency below 14mhz I feel I must try a
vertical in a side yard located outside the shack. The area is
about 25X40 feet. Radials can be put down in that area There
is a 50' tower with a triband beam in one corner of that area.
No other metal is in that area. The feedline length to the
shack is about 20'. There is no height restriction in this
area. I only need the antenna for 75 and 40. There is a 6'
tall wood privacy fence around this area. I would hope that
using a vertical in this area would fix the rfi problem since
the antenna would be a good 40' away from the entertainmant
center whe
re
as the center of the dipole is directly above it. Suggestions
please. WB5OXQ
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