[AMRadio] BC1-J Mod trans. is fine.

[Dan Hall]

I'm not worried about it yet but I suspect that it is audio feedline
shielding. The processing gear is on the desk, the driver amp is on the work
bench, (20' away) and the tx is in the middle with the back off.

Dan
----- Original Message -----
From: <wwd at netheaven.com>
To: <amradio at mailman.qth.net>
Sent: Thursday, March 21, 2002 9:57 AM
Subject: Re: [AMRadio] BC1-J Mod trans. is fine.


> Unless his audio shielding is /really/ poor, rf getting into the audio is
> ultimately an antenna/feedline/tuner issue IMHO. When you get rf-zapped by
> your D-104 you have an antenna problem. When you hear rf on the other
> guy's audio, he has an antenna problem 9x out of 10. Bad connections, bad
> design, wrong tuner, need for fresh feedline, etc.
>
> Even though your tx is near the ant tuner, it helps to use 25 to 35 feet
> of coax kept in a coil- really smoothes things out (choke balun). But do
> these things too- they are important. 'Course then you've lost your
> 'rf-canary'.
>
> I've pumped out a solid kw for years with "no" rf in the shack. The tuner
> is 10 feet away up on the wall - twin roller inductors, the big ones, and
> a big vacuum variable) fed by 35 feet of coax mostly in a tied-up coil.
> >From the tuner is ladder line exiting thru the wall. Maybe once I had rf
> on my audio signal, zapped myself on the D-104, and then found the
> connection that had popped off. Bill    N2KQA
>
>
> >Modulator oscillation when the TX is on the antenna is probably caused by
> >RF getting into the audio circuits and being rectified, producing audio
> >which results in feedback.  Add RF filtering to the audio inputs; a few
> >turns around those square Radio Shack cores helps too.  If everything is
> >open, try shielding too (closed boxes, etc).
>
> >  Bacon, WA3WDR
>
>
> >> >> works fine into a dummy but the
> >> >> modulator oscillates when into the antenna. I still need to
> >clean up the
> >> >> transmitter side of things. But there's hope.
> >> >>
> >> >> Dan
>
>
> --
> --------------------------------------------------------------------------
-----
> wwd at netheaven.com  To the warriors go the spoils of war; to the hindmost .
.  the surplus.
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