Before you tear it all apart, try this:
Insert an RF choke in the coax line between the 238B and the Jupiter.
I have run that same design with 1000w and not had the problem.
I always put the choke between the transceiver and the amp, and another
choke between the amp and the matchbox.
Make sure your station is grounded properly.
I also use an external balun. I don't use the built-in balun.
I use a very simple coax balun (24' for RG213 wrapped on a 4" PVC pipe, with
a 10" stub into the 238B).
I work all bands with this.
I am not speaking of once and getting lucky.
I have done this at several different QTHs with combinations of a couple of
different amps and about 6 or 7 different Ten-Tec transceivers including the
Jupiter. Most recently with the Eagle.
I sometimes had trouble as you are having, but a proper ground AND these RF
chockes did the trick.
From: firstname.lastname@example.org [mailto:email@example.com]
On Behalf Of David
Sent: Monday, January 10, 2011 6:52 PM
Subject: [TenTec] ballun suggestions
Please bear with me for a few minutes while I explain the situation. When I
purchased this house it had a 10 foot section of tower in the back yard with
a basket ball hoop and back stop on it. I removed the basket ball stuff and
installed 20 feet of fiberglass camo support poles and an inverted V with 23
foot long elements of wire. I also had a SGC 230 at the top of the pole to
tune the antenna. Well the SGC has failed for the third time and I decided
not to pay for the repair but to go with a manual tuner. So I talked to
Stan at ten tec and got a used 238B . I then ran 300 ohm transmission line
from the antenna to the tuner on my desk. Tune up at 20 watts no problem 10
thru 40 meters. 40 meter SSB no problems. 20 and 17 had comments of RF in
the audio at 100 watts from the Jupiter. 100 watts on 15 drove the Jupiter
nuts with display blanking and shut down of the transmitter. So I am now
plan to take down the V and replacing it with a vertical wire 19 feet long
he fiber glass pole and 4 elevated radials just above the top of the tower
section . Idea #1 is to run 15 feet of twin lead from the top of the tower/
base of the vertical to the house and a balun on the outside wall and 8 feet
of coax to the tuner. Would a 1 to 1 or a 4 to 1 ballun work better? Idea
#2 is a 4 to 1 unun at the top of the tower and base of the vertical and 28
feet of coax to the tuner. Given the 30 foot total height restriction I
have to live with I am thinking the vertical might be the better DX antenna.
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