Qualtek makes a neat little filter designed to replace the power input connector on a noisy supply. It fit into mine - one of those with the jumpered filtering components - and completely suppressed any audible noise. According to the schematic on the side, it consists of 2 x 2.5 mH indutors, one in series with each leg, a 2200 pF cap shunting the line input and 0.1uF capacitors from each leg to ground on the load side. Their part number is 858-03/007, and I got mine at Mouser.
73, Pete N4ZR The World Contest Station Database, atwww.conteststations.com The Reverse Beacon Network athttp://reversebeacon.net, blog at reversebeacon.blogspot.com, spots at telnet.reversebeacon.net, port 7000 and arcluster.reversebeacon.net, port 7000 On 7/4/2012 12:14 PM, Jim Brown wrote: > On 7/4/2012 6:10 AM, Bill Cromwell wrote: >> Next I'll be getting my hands on some ferrite core materials and looking to >> see just how far I can reduce the noise. > When faced with a noisy computer, the first thing I'd try (other than > replacing the noisy supply) would be a multi-turn choke on the power > cable, optimized (number of turns and core) for the band(s) where you're > hearing the most noise. If noise remained, I'd next tackle the video > cable and the printer cable. Use the graphs in Appendix One of > http://audiosystemsgroup.com/RFI-Ham.pdf as a guide to picking the cores > and winding the chokes. > > Do your fellow hams another favor -- post the brand names and/or vendors > of both the noisy power supply and the one that fixed your problem (if > it does). :) > > 73, Jim K9YC > _______________________________________________ > UR RST IS ... ... ..9 QSB QSB - hw? BK > _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK