I have a similar problem with a battery charger inside the transfer switch cabinet for my backup generator. It's a switcher. The outputs run through 30 ft of #14 wire in plastic conduit out to the generator. I could hear the signal every 101 kHz starting at 404 kHz and running up to over 5 MHz. An IC-R10 receiver would pick it up strongest at the generator itself. The only way I could get rid of the radiation was to remove the DC connections to the wires running to the generator. The manufacturer sent me two clip-on ferrites for the DC wires but they had no effect. Their recommendation was to replace it with a linear charger, which I have acquired but not yet installed.
This was hard to find, too. I turned off each circuit breaker in the panel but none got rid of the signal. Eventually I even pulled the main 100A breaker; THAT finally made things quiet. Of course, the only thing that was directly connected to the raw incoming power was the charger inside the transfer switch. All the metal shielding did nothing for it. It's amazing how 101 kHz harmonics can ruin spectrum analyzer traces for the AM broadcast band ! Bob M. ====== --- Dave VanHorn <[EMAIL PROTECTED]> wrote: > > Well, in the end, it turned out to be the IOTA power > converter. > > This is something that didn't show up in extensive > testing here, and > didn't show up at the site for a while either. > > With modern SMPS designs, you can't really use the > term "switching > frequency", since the controllers do things like > pulse skipping > under light load, or frequency modulation to > "spread" the noise > making part 15 easier. Even an older switcher that > runs at a fixed > frequency, will be doing PWM, so there will be > another frequency > component that moves around under load. > > However that works out in the IOTA, it was apparent > that this was > the source. I was able to hear broad hash on my > IC-R3 held close to > the unit, and tuning up to the repeater input, I > could hear the mix > product as well. I replaced it with a linear supply > since I had one > handy, and the problem's been totally gone for over > a week. > > :) > > I spoke to IOTAs technical people, who were pretty > knowlegable. > They offered to exchange the unit, and came up with > the same > probable fix that I did, ferrites on the line cord > and DC cables. > Since the unit is in a metal box, I think that this > will likely > solve the problem. > > Key symptoms of this problem: > Comes and goes. > Gets through CTCSS squelch, IF you encode the same > tone you decode. > (because it's mixing your output back in) > Has audio that sounds like an echo or fast repeat, > but the audio is > rather weak. > > Cause: Repeater output mixing with switching power > supply noise, > producing a real carrier on the repeater input. > > Won't happen on a 440 machine, or probably a 220 > machine, due to the > wider splits. Switchers are increasing their > operating frequencies > to keep the magnetics small, so having significant > noise at 1.2 MHz > bothering a 220 machine isn't out of the realm of > possibility. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
