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Author Topic: RFI from Astron VS-35M Power Supply  (Read 6113 times)
N5EG
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Posts: 331


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« Reply #15 on: September 11, 2015, 09:27:44 AM »

This doesn't 'smell' at all like a problem with the Astron supply.
Without knowing the details we can speculate that there is 60 KHz-rate
noise on your AC power lines, and using the Astron merely provides an
ingress route for that noise to your radio from the AC power lines.

There's a couple of ways to check this:

1. Turn off all the breakers in your house except the one feeding the Astron
and see if the 60-KHz stuff is still there. If it's gone, you know that something
in your house is injecting it onto your AC power lines.

2. If that doesn't work, the noise source might be on the same breaker as the Astron.
Try using a long extension cord to plug the Astron into a outlet controlled by a
different breaker, and turn off all breakers except that new one.

3. If neither of those work, wrap the AC power cord of the Astron through a ferrite
common mode choke (Mix 31) several turns.  For the duration of this test make sure
there are no sneak paths to ground from your transceiver (which could short out the
ferrite choke), but only the path to ground through the power supply / ferrite choke.

If any of these steps succeed, you know it's not the power supply but something else
on your AC line.  60 KHz is a very common switching power supply frequency, and the
identifiable clump on the panadaptor suggest this.


-- Tom, N5EG



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WA2ISE
Member

Posts: 1192




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« Reply #16 on: September 11, 2015, 09:58:32 AM »

I have a Samlex switching power supply that emitted crud every 60Khz or so, found this mod quieted it down: http://www.qsl.net/gm3woj/sec1223mod.htm

But IIRC yours is a linear supply, but maybe the LM723 is misbehaving.  
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