[Elecraft] Power Supplies

[Kevin - K4VD]

Hi... I have a KX3 and normally run it on batteries. I also have a
Flex-6500 that runs on a big RS-50.

Last night during the QRP Fox Hunt (only 1 pelt) I decided to shutdown the
Flex and give the KX3 a shot. I powered up the Flex on its internal
batteries and, while I had the headphones on, plugged the RS-50 into it.

I was surprised with what I heard. Not only a low freq hum (60 or 120 Hz,
can't tell) but also a hash sound. The affect was fairly dramatic. I never
noticed anything on the Flex because I never ran that on batteries.

Today I swapped the KX3 between an old RS-12 linear I had laying around, a
12 V 15 Ah LiFePO4 battery pack and the internal batteries.

Going from internal (9.9V) to LiFePO4 (13.0V) I could hear no difference
and see no difference on the S-meter. I tried with the antenna connected
and disconnected.

Going from internal to the RS-12 (13.5 V) i could hear an increase in noise
level, about +S1, almost like turning up the RF gain a tad. When the
antenna was removed I heard no difference between internal battery and
RS-12. The additional noise wasn't objectionable - just sounded like the
noise floor jumped up a bit. No hum, no hash (or hiss).

I'm not sure what to make of this. It is apparent my RS-50 is in need of
some attention. I've had hit-and-miss experiences with Astron over the
years and now seeking an alternative. I just want something to work and
work well. I'm not even sure the RS-12 is up to spec with the small
increase in noise. My expectation is no change in noise going between
battery and power supply. Is this unrealistic?

eham's reviews are kind of not very helpful. There's plenty of good and
plenty of bad said about most makes and models. I'm thinking maybe I want
to run 100% battery for both the Flex and KX3 and just recharge when not in
use but I'm not sure how realistic that is. I do know I don't want to just
settle for the additional noise.

Switchers don't seem to be an option. While it might sound quiet at the
moment I can always see/hear that noise snake crawling across the panoramic
display right towards my current QSO.

Has anyone done some A/B comparisons while listening? I'm curious what you
may have experienced.

Thanks,
Kev K4VD
(VD = Vacation Day)