[Elecraft] How to Eliminate Power Supply Birdies?

[Bill K9YEQ]

Exactly why I sold mine.  It is noisey and basically worthless to me.
Perhaps the newer ones work better.  I am using other more recent switching
supplies that don't give me any issues and they are a whole lot less
expensive.


73,

Bill
K9YEQ


-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bob
Sent: Monday, January 11, 2010 6:30 PM
To: elecraft at mailman.qth.net
Subject: [Elecraft] How to Eliminate Power Supply Birdies?

 I  have an Alinco DM-330MVT power supply that has significant birdies on
160M. The power supply has a nice feature that allows you to move the
birdies, which makes it obvious that the birdies are originating from the
power supply.  The birdies are at least 1 S-unit above the background noise.
Here's what I've done to try to eliminate them:
-  added a filter connected to the DC output consisting of 4 toroid beads
(type 77) in series on each side and 0.1 caps across the leads and from each
lead to ground.  I  also have both leads going about 10 turns through a type
77 toroid to filter common mode birdies.  
- I've put 2 snap on type toroids on the AC line  as well as wound the ac
cord through a T200-1 toroid (which I had lying around) .  
- I shielded all of the power leads from the power supply to all of the
equipment that it powers (mostly my K2, KAT100 and external speaker/amp),
with the shields connected to both the power supply and the K2 chassis
grounds.
- I've moved the power supply away from my K2 (about 5' away).
 
 All of this seems to have absolutely no affect on the birdies.   To add to
the mystery, the birdies are there only when I have an antenna connected to
the K2, so it would appear that the Power supply is radiating, but with all
of the wires to it filtered and the DC lines shielded, where can it be
radiating from - (as a test I put the whole power supply inside a metal file
box and grounded that to no effect.
 
So,  can anyone explain this?  Other than buying a new power supply, what do
I do now? Except for the birdies on 160M, this is a nice power supply that's
small enough to fit into an attaché case with my K2, KAT100, mic and key.
 
Thanks.
 
Bob W1SRB
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