[Elecraft] Power Supplies

[Vic Rosenthal]

You can tell if the noise floor increase is due to increased gain by seeing if signals increase in strength along with the noise.

As Don said, OCFs are prone to common mode issues. Perhaps the power supply is acting as a ground return for the 'common mode antenna'? A common mode choke on the power leads as you suggest might be worth a try. 

Regarding clip-ons, remember that at HF you need multiple turns to have a noticeable affect. Also make sure they are the correct types of ferrite. The K9YC paper deals with that.

Vic 4X6GP

> On 16 Jul 2016, at 00:01, Kevin - K4VD <kevin at k4vd.net> wrote:
> 
> 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