[Elecraft] AC hum on tune

[Tom W8JI]

> I just went to battery power and hear the same hum
>
> I have turned on a radio shack swl receiver sitting across 
> the room
> and am using 0.10w output
> into the same antenna (dipole 24 ft up on roof)
> So now I hearing what I think they were talking about
> it's not exactly what I would call an 60 cycle ac hum
> but it does modulate the tune signal at a low frequency 
> rate
>
> Ok  including what should answer others posts as well.
> the only other ac field near by is a computer switching 
> supply about a foot
> below, I don't think switching supplies create the kind of 
> fields we are talking
> about in other posts?


Sam,

It is common for me to hear hum or buzz on local receivers 
very near a transmitter. Even on perfectly clean 
transmitters unless I use a line tap to sample signal all 
sorts of stuff mixes in. I've never really looked into why. 
My guess would be it is some nasty multipath being modulated 
by something. Just a guess.

I'm not saying you don't have hum, but just cautioning you 
to be careful when listening on a local receiver near a 
transmitter. I can replicate hum on my shop receivers even 
with a very clean transmitter on the bench.

That aside, did you try disconnecting everything except the 
K3 antenna and power supply?

Switching supplies do not normally cause 60 or 120 Hz 
problems.

73 Tom