I second Rob's recomendation about using the RadioWorks Line Isolators. In
fact they now have low power versions which aren't so expensive.
Someone hinted at this in an earlier post, but there's no such thing as
"the" cause of these problems. They can be one or many and differ from site
to site, even using the same equipment.
My hobby has always been going on expeditions for contesting which meant
building stuff in a hurry, catching a few hours sleep, then 48 hours of
contesting. There's not a lot of time for sorting ground loops.
There has been lots of recomendations on this thread as to how to approach
the problem and I'm sure many come from hams and/or engineers that know far
more about the subject than I do. What I do want to say is that often these
RF Line Isolators are quick fixes for strange problems going on with your
transceiver (i.e., all bands work just fine except on one band, say 15m,
which won't put out full power without the rig shutting down). I've had
this dozens of times and solved it with one or two line isolators.
Sometimes I placed it directly in the antenna line where it connects to the
linear, but most of the time I placed it between the Transceiver and the
Amp. Sometimes I did both. In the meantime I always place a line isolator
between my transceiver and my linear as standard operating procedures. For
this, the low power (low cost) version works just fine.
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Rob Atkinson, K5UJ
Sent: Thursday, April 22, 2004 8:18 AM
To: tentec@contesting.com
Cc: k5uj@hotmail.com
Subject: [TenTec] RFI and Orion Mic connector - bad info
I used to have my basement shack at the end of a 20 foot ground cable. I
was getting back into the game after being off HF for many years and I
(obviously) had forgotten a lot about station building if I ever knew
anything to begin with. I moved the whole shack and cut the ground run down
to about 5 feet. Are you really sure you can't get closer to your ground
rods? If not, I can only think of 3 options: 1. Tuned ground
"counterpoises" one for each band or a matching network for one wire (MFJ
"artificial ground"). These are wires cut so that on whatever band you want
to use, one of them will be at a low impedence at your rig's ground lug. 2.
Not having any ground at all. Some hams claim this works for them but I'm
not convinced it's a good idea. 3. Drilling a hole or holes in your
basement floor at your rig and sinking a rod or rods through the concrete.
Invest in a bag of 20 or 30 split bead ferrite chokes and put them on
equipment leads. (the brute force approach) Expensive but you will be
amazed at how quickly you wind up using them. If a lead has a shield and
the shield is only for that and is grounded at both ends try grounding it at
only one end (the nonOrion end).
Take a look at this approach to deal with RF coming back in on the shield of
coax feedline:
http://www.radioworks.com/nliinfo.html and coax ground loops.
While this ham is naturally trying to sell his line isolators, the
information contained here
is still useful and worked for me as a solution.
I had awful RF problems with a Omni VI running 1 kw because my antenna is
only 20 or 30 feet from my shack. I shortened the ground run, used ferrite
chokes on equipment leads, employed line isolators and the radioworks ground
configuration and these techniques fixed my problems.
since this could be overkill for you, try what Bob said about testing one
lead at a time.
Rob Atkinson
K5UJ
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