The K3 has a CONFIG menu entry called "AFSK TX". If you set it to "FIL ON", a 400-Hz transmit-mode audio filter is inserted, centered around the mark/space tones. This is only available when the rig is set for AFSK A mode. It should be effective against low-frequency hum coming in through the mic or LINE IN connectors.
73, Wayne N6KR On Sep 28, 2009, at 2:45 PM, Leigh L. Klotz, Jr. WA5ZNU wrote: > Jim K9YC wrote: >> 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. >> ... >> 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. > > Note that the upcoming firmware upgrade will reportedly eliminate > TXEQ in > AFSK (and other audio-based digital modes), and it apparently may be > some > time before another update provides true per-mode TX/RX EQ. So people > with hum will need another solution, except for the voice modes. > > I tried wrapping the component side of the transformers in a sheet of > Mu-metal (actually, a competitor, not Mu-brand) and noted no > difference. > It was probably a futile effort anyway as it didn't wholly enclose the > transformer; probably I need to complain to Maxwell about this. > > Leigh/WA5ZNU ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
