[Elecraft] AC hum on tune

[Sam Morgan]

This one is a bit hard to describe, so please bare with me.

I was talking to some locals (1-5 miles) this morning on 80m LSB.
I was told that when I was tuning up a hum was heard on my signal
by the guys, which were in LSB on their receivers

I tried with low power 1w
I tried with higher power 90w
I tried it through the external amp
I tried it with the external amp off
I tried it direct to the antenna
I unplugged everything from the K3 but the power and antenna
I have switched power supplies,
I have switched AC outlets in the room.

They say they still hear the hum.

I switched to cw and
when they were still listening in LSB,
they still heard the hum on my cw signal.

IF they switch to cw on their rigs,
they do NOT hear any hum on my cw signals.

what in the world is going on here?
do I have a problem or not?
-- 
GB & 73
K5OAI
Sam Morgan