[BC] Noisy Audio Chain

[Jim Tonne]

Tom:

I would place money that there is an STL in the system
and what you are hearing is white noise due to that.
If that noise is down, say, 65 dB, and an AGC at the
transmitter is "opening up" to the tune of maybe 15 dB,
then that noise will be down 50 dB.  Tune to either side
of carrier and the white noise will be very very apparent.

- JimT





----- Original Message ----- 
From: "Tom Dimeo" <mwam at box311.net>
To: <broadcast at radiolists.net>
Sent: Sunday, December 03, 2006 7:45 PM
Subject: [BC] Noisy Audio Chain


> Quite often WWII 720 leaves their carrier on all night. There 
> is so much high frequency noise on the signal that I can hear 
> it eight to ten kHz on either side of center. It sounds like 
> there is a blank tape playing. There is also some sixty and I 
> think one hundred twenty Hz hum on the signal.
> 
> Is it normal for an audio chain to be so noisy? I realize 
> that the audio processing will bring up the noise but it is 
> much louder than I'd think it should be.
> 
> My experience goes back to the sixties and I know what noise 
> modulation like this would do to the modulator tubes of the 
> transmitter, is it as hard on a solid state transmitter?
> 
> 
> Just curious.
> 
> I've given up calling the station and telling them about the 
> transmitter being left on. Shortly after the last time I 
> called them one of the owners died.
> 
> Tom
> 
> 
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