What you want to do is pretty simple to explain - but harder to implement.
You have to keep the common mode and overload issues contained - and the
only way to do that (other than physical separation) is to choke it but I
can tell you from personal experience that it's not a cheap process. The
higher the power level, the tougher it gets.
For the gear, you say you are choking it. But the devil is in the details
here. If you want to run gear near the antenna, type 31 ferrites will
probably let you do that but you need to understand the threshold effect.
If none of this makes sense, search on K9YC and RFI primmer.
For the antenna, dump the open wire and the shack mounted tuner. Get a
remote tuner which can be mounted at the dipole feedpoint. Open wire
feeders are finicky about balance and if you have things near this line, it
will disturb the balance - and result in feedline radiation. Put a serious
coax choke up there with the antenna (that means more ferrites - not the
6-turn air coil traditional type). There is a K9YC presentation on Coax
Chokes.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: Stan Stockton
Sent: Tuesday, November 19, 2013 11:38 PM
To: Jim in Waco wb5oxq
Cc: <TowerTalk@contesting.com>
Subject: Re: [TowerTalk] Limited space for 80 and 50
Jim,
You already have the vertical. Shunt feeding the existing tower is my
suggestion.
Stan, K5GO
Sent from my iPad
On Nov 19, 2013, at 9:57 PM, "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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