[Elecraft] How to Eliminate Power Supply Birdies?

[Bob Nielsen]

I have the same supply and have never had any birdie problems with it  
in 9+ years of use (although being antenna-challenged, I don't  
operate much on 160).  In the QST reviews of switching supplies  
several years ago the Alinco did pretty well compared to most of the  
competition, but I suspect that some supplies are more prone to these  
issues than others.

I solved most of my birdie issues by switching from a CRT to a LCD  
monitor on the shack computer.

73, Bob N7XY

On Jan 11, 2010, at 5:32 PM, Bill K9YEQ wrote:

> 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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