[WriteLog] Hum in Audio

Tom McDermott tom.mcdermott4 at verizon.net
Tue Apr 6 19:34:10 EDT 2004

The phone patch input and the mic input are effectively wired in parallel in
the FT-1000MP, and I suspect its similar for the FT-920. The computer
soundcard is blasting up to a volt of audio into the patch input
overwhelming any audio from your microphone. You need an attenuator from the
soundcard to the computer to reduce the levels and get rid of the hum while
keeping the mic input to the radio unchanged.

While the suggestions for an audio transformer are fine, the transfomer
isolates noises caused by a millivolt or two of ground voltage, while the
souncard is throwing hundres of millivolts of noise at it.

If you plug the MIC into the soundcard you will have the reverse problem,
the mic level is way too low for the soundcard. Some soundcards have a
selectable +20 dB boost (on the mixer input dialog box), but I find mine to
be somewhat noisy, and an external op-amp mic amplifer sounds a lot better.

	-- Tom, N5EG

Apprently, this is a common problem with FT-920's and their mic inputs.

I don't know the resolution.
From: "Magnus A" <sm6wet at telia.com>
Date: 2004/04/06 Tue AM 10:13:00 CDT
To: <writelog at contesting.com>
Subject: Re: [WriteLog] Hum in Audio

I tried that too, and I tried with only 5 watts, still the same problem.
Could it be that the problem goes away if I trancieve thru the comp (connect
the mike to the computer instead of radio)????
Anyone knows?

73 Magnus

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