[Elecraft] Power Supplies

[Kevin - K4VD]

Thanks Dick and Howard...

The RS-50 is pretty new - maybe 6 months old and is in daily use. It wasn't
until I had a rig I could easily run on batteries did I notice the noise.
The RS-12 is quite old, maybe 15 years? It had been in storage about 10
years until trying it out today. I think I need to dig into the RS-50 and
just make sure everything is soldered and connected well.

As for common mode currents in the antenna... would that only be an issue
during transmit? I have an OCF so I know it can be an issue on transmit.
The OCF has a 1:1 current BALUN in the center. Is that enough or do I need
to add some additional choking just below the BALUN? I have a couple of the
NI4L line isolators (http://www.ni4l.com/hf-choke-line-isolator-1-8-300-mhz/).
I could put one up there and see what it does. I also have plenty of
clip-ons laying around. I'll try them on the power lead from the supply to
the radio.

The reports above were with *receive only* (with and without an antenna
attached). On the RS-50 the hum I'm hearing is what I think I'd expect to
hear from a less-that-well filtered linear power supply. The hash/hiss
noise I hear sounds more like a switching power supply, which it is not. I
don't know what in the power supply could be generating that noise.

The RS-12 does not have either the hum or hiss that I can hear. It just
sounds like the noise floor bumped up a little. I'm thinking Dick is right
and it is just the receiver responding to the increased voltage though it
is only about .5 volts above the external battery pack I was using.

Is every power supply going to generate a little noise or should I expect
no difference moving from battery to power supply?

Kev