The RFI is almost certainly common-mode and is being radiated by the AC power cord -- and, by extension, the house AC wiring. Your typical store-bought "AC line filter" is a differential-mode device and will do nothing to abate common-mode currents. What you need is a common-mode choke on the AC input cord, installed as close to the power supply case as possible. You make a common-mode choke by obtaining a fairly large ferrite toroid and wrapping it with the AC line cord. (Then use an extension cord to reach the wall outlet.) Palomar Engineers and a couple of other vendors sell these, and they have info on their websites that will help you choose the best ferrite mixture for the frequency bands you're most concerned with.
Or, you can do like I did, and ditch the switcher. Get a "big iron" power supply, like my Astron RS-70M. No birdies, no problems. :-) Bill W5WVO -------------------------------------------------- From: "Bob Nielsen" <n...@clearwire.net> Sent: Monday, January 11, 2010 7:31 PM To: "elecraft List" <elecraft@mailman.qth.net> Subject: Re: [Elecraft] How to Eliminate Power Supply Birdies? > 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 >> >> ______________________________________________________________ >> 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 > > ______________________________________________________________ > 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 > ______________________________________________________________ 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
