[RFI] My Station RFI Sources

[Jim Reisert]

> PC: Various birdies leaking from all cables. Strong broadband hash 
> that, I believe, is coming from the switching power supply. This hash
> is not affected by unplugging all cables from the PC.

The root cause of this problem is that there is supposed to be a line
filter in the PC board in the power supply, but it's usually just
jumpered through with bus wire (can you say, make 'em cheaper?).
You'll have to open the supply, then you'll probably see the footprint
on the PC board where the filter should have been.

I had some ferrite cores that had been used as line filters in an old
poer supply I found in a trash heap at work, I took a pair of wires
from a 4-wire telephone cable, twisted them together and made a
bifilar winding of as many turns as I could on the ferrite core.  Then
I removed the bus wires and used this new 1:1 transformer that I had
wound instead.

My worst problem was on 160, and the noise went down by 30-40 dB.

- Jim AD1C
  AD1C@contesting.com

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