Switching supplies tend to have their worst noise problems on the low bands because those are the lower (stronger) harmonics of the switching frequency and the noise filtering tends to be less effective at low frequencies.
It sounds like the spurs are coming out the power line. If the Alinco supply does not already have a line module with built-in filter you might see if you can find a filtered module that would fit. For example, here's one I was looking at recently. ($12.58 in single quantity) http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=817-1499-ND It has a PI filter with 0.1 uF, 0.3 mH (2) and 2.2 nF (2) which ought to give 30 or 40 dB attenuation on 160 meters. Or you could search the Digi-Key site for separate line filters: http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=3408328&k=line% 20filter Al N1AL On Mon, 2010-01-11 at 18:31 -0800, Bob Nielsen wrote: > 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-boun...@mailman.qth.net > > [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Bob > > Sent: Monday, January 11, 2010 6:30 PM > > To: elecraft@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 > > ________ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
