G. Doughty wrote:
I have an issue on 40 meters from my tentec scout 555. After the rig
is tuned (mfj 901b) and I tx cw, I get an AC hum in my headphones
on every key down. This doesn't happen when my audio comes from the
rig. I am using an alpha delta loaded antenna in the attic and it is
almost certainly putting the tuner to a test. Is there something I
can do to alleviate this problem?

So where are your headphones plugged when you hear the hum?

When I'm sending CW on my Icom 751 at full power with the tuner loaded
for very low SWR, I hear a pretty good AC ripple over the sidetone. I
think it's because I'm dragging a lot of power out of the supply, and
it doesn't regulate as well at those power levels as it does at lower
levels.

It's not a high enough level to make me think it's a problem; I don't
know about your hum, but wonder what a scope would show.

--
Mike Andrews W5EGO 5WPM
Extra
Tired old sysadmin working on his code speed