[RFI] 80M noise
jim at audiosystemsgroup.com
Tue Sep 10 23:18:27 EDT 2013
On 9/10/2013 7:20 PM, Larry Bryan wrote:
> but I did discover when I took the
> Tecsun outside that I have a large noise from the dipole coax. If I get
> anywhere near the lead in, the radio goes full scale. Same type noise I'm
> hearing on the Flex.
That may or may not mean anything. Inside the portable radio is a loop
antenna, and it will usually couple to any wire passing by it, which
couples any signals (and noise) current on the wire into the radio.
One thing to check -- look carefully at the Flex radio and make sure
that the body of the coax connector for the antenna is screwed down to
> My antenna is a Tennadyne TD-90HP800 folded dipole in a inverted V
Ah, the famous dummy load antenna -- that "termination" burns half of
the TX power on some bands, which is how the antenna gets to be
> Coax goes into a balun at the feed point of the antenna. The
> balun is part of the antenna package.
There are at least a dozen different things that are CALLED a "balun,"
and they all do very different things. The "balun" that came with the
antenna is probably useless. Many commercial "baluns" are.
> Just looking for some feedback on this issue.
What you NEED up there is not a magic box called a "balun," but a
serious common mode choke. Study http://k9yc.com/RFI-Ham.pdf and use
the Cookbook to tell you how to build what you need. I suggest one of
the bifilar types.
I also suggest you build a much better antenna -- that dummy load is a
73, Jim K9YC
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