Wow - this is strange! 1) Are all the K3's enclosure screws tight? Have you tried tapping or lifting the K3 while listening to the hum (looking for an intermittent connection)?
2) Does the hum remain if you key the rig in CW mode? 2) If you move the K3 and battery supply to a different location (room perhaps) does the hum remain? Your needing to cut up to 400 Hz is not surprising. It's not unusual for 60 Hz hum to have a number of harmonics if the waveform is getting distorted in the process of being picked up. The fact that it's being picked up with AC disconnected to everything in the room suggests that it's a fairly high-level high-impedance circuit picking it up. Such circuits can pick up 60/120 Hz buzz from many blocks or miles around. BTW, I can't imagine how an external ground would have an effect with nothing connected to the K3, but if you're thinking of checking outside, now's the time. I see we're due for snow at low elevations in the Northwest by tomorrow night. Ron AC7AC -----Original Message----- As noted in a previous post, I disconnected EVERYTHING. Nothing on the back panel of the K3 at all except for a Li-nano-phosphate battery as my power source. All AC off at the breaker panel for this room. The only electrical equipment on was my K3 via the battery and my Macbook Pro laptop via its battery. Given those conditions, the hum was still there. Jim Brown suggested that I consider TXEQ to cut off the low frequencies, I did max cut for all frequencies up to 400 Hz. The hum did not start being attenuated until 400 Hz cut. But, max cut on 400 Hz did not attenuate it completely. I did not do higher frequencies. So, anyone who might help -- where does this hum or buzz come from if nothing is connected to the K3 and there is no AC flowing anywhere in the room. It is 28 degrees outside, which is freezing cold plus for the northwest and I am not used to that but my next step is to go outside and check my grounding to ground points. phil ______________________________________________________________ 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
