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[TenTec] RE: RFI to power supply speaker

To: <tentec@contesting.com>
Subject: [TenTec] RE: RFI to power supply speaker
From: rohre@arlut.utexas.edu (rohre)
Date: 13 Oct 1997 11:53:51 -0500
Webster, now you are getting to the heart of the problems. The computer based
DSP circuit.  And the loop with coax feed.

Well, I can predict that the RF ground you have now, depending on whether the
rods are over a marsh or the sea shore, are not going to help much with your
present problem.  What you can do, is consider setting the RS DSP into a
preferably steel box to both magnetically and electrically shield it.  And use
some chokes on as I described, close to where each wire leaves the unit.  Make
sure it has twisted pair power leads, or use shielded power leads.

Another easy thing to dampen down the RF inside your station, is to install
some quarter wave counterpoises from the rig ground screw and stretch them out
around the shack or even outside if you can.  You might be able to improve
things somewhat, even attaching them outside the shack as close as possible to
the main #6 ground entry to the shack.  But the fact you are measuring an
increase in field strength on the OUTSIDE of the PL 259 shows you have RF on
the outside of the coax.  With a loop you need a balun.   That should help the
RF on the coax thing.  You apparently have both the RFI of the RS DSP, and the
RF of the antenna to deal with.  You might consider running the DSP on its own
battery supply and NOT in common with the rig, and it would truly be floating

Good Luck,
Stuart K5KVH

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