[Elecraft] K3 Power supply

[Milt, N5IA]

----- Original Message ----- 
From: "Merv Schweigert" <k9fd at flex.com>

> I started to try and find the problem and using another
> receiver I find the Astron SS-30 is generating all sorts of noise.
> I have used this supply for some time and have not noticed the noise
> before.

Merv,

For weight considerations, the SS-30 supplies were selected for the Ducie 
Island expedition this past year.

This problem you mention, or a very similar one, was evident during the 
VP6DX expedition from the time that Robin started making tests while 
underway on the Braveheart from ZL to FO.

We added extra filtering internally.

We grounded extensively.

We cleaned the case cover screw holes both on the main chassis and on the 
cover to improve bonding to the cover.  We were never able to make them 
clean.  All supplies performed in the exact same manner.

We were float charging small batteries to keep the K-3s and the ancillary 
equipment running while the gensets were being refueled and having oil 
changed.  The extra capacitance of the battery helped with the DC filtering 
but most of the stuff was of a frequency that the battery and other 
filtering could not remove.  And we couldn't keep it inside the case.

The fact remains that the harmonics of the switcher were a very real problem 
for us, especially on the lower frequency bands.  The most annoying 
situation was the harmonic signal moving around, slowly up and down the band 
such that we could not avoid it at times when we were in the middle of a 
tough one on 160 and were trying to dig it out of the noise floor.  We had 
to wait until the birdie slowly slithered on by or many times I just reached 
and turned the SS-30 off during a difficult contact.

73 de Milt, N5IA