Would wrapping some of this "Ultraperm 80" shielding around the K3's audio transformers be a solution?
(http://www.goldmine-elec-products.com/prodinfo.asp?number=G16600A) 73 -- Joe KB8AP On Sep 28, 2009, at 12:06 PM, Jim Brown wrote: > On Mon, 28 Sep 2009 13:29:54 -0400, Brian Machesney wrote: > >> The problem only occurs in an >> SSB mode when the nearby PA is both on and enabled (i.e., not on >> "standby") >> and when the K3 is both within about 8-in of the PA and parallel or >> at right >> angles to it; rotating the rig about 15 degrees around the z-axis >> eliminated >> the hum. All in the usual vein, so far. > > Magnetic field coupling from the power supply to the K3's input > circuitry, > probably due to the use of unshielded audio transformers in the K3. > This is a > well known problem. One good band-aid is to go to the TXEQ1 settings > and fully > cut the three lowest octave bands. There's little communications > value to the > speech below 300 Hz anyway, and it burns TX power, so it's a win- > win. Also, > the acoustic stuff in that lower frequency range includes breath > pops and room > noise. > > It's also possible to have magnetic coupling on input wiring if > you've managed > to form it into a big loop, but the transformers are the more likely > cause. I > ran into the loop problem once when I jury-rigged a headphone amp > for SO2R. No > problem in TX audio, but it was in my phones. One of my neighbors > had so much > magnetically coupled hum into the Line In transformer that it > regenerated to > full output power when he tried to run RTTY in AFSK mode. > > 73, > > Jim Brown K9YC > > > ______________________________________________________________ > 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
