[Elecraft] recommended switching supply

[brianb]

Jim,

I now own an astron ss25 (20a continuous) supply. It works well. Here is 
my expereince.
I have borrowed a low cost supply that is sold through HRO, 20 amp 
rated. I was going to Fiji on  a surfing+DXpedition and needed light 
weight. I tested the supply at my home in San Jose on the frequencies I 
would be using. All was well but I really only paid attention to the 
noise prior to transmitting a few times. There seemed to be no 
appreciable noise.

When I got to Fiji and set up the station on a very remote island with 
no electrical devices there was no noise. As I began to operate I 
noticed "hash" would drift through my receive frequency as the power 
supply heated under the transmission load. With heating the PS internal 
oscillator was drifting a bit and harmonics of the swithch frequency 
would drift through the rcvr passband. This noise level was very low but 
very noticeable in such a quiet environment. I was working large pile 
ups and when the hash would land on the freq. I would have to work the 
loud sigs until it passed.

The astron does this as well but the level is quite a bit lower than the 
cheaper model. Also, the astron noise is not noticeable when my ambient 
noise around the house/city is at normal levels.  I am not sure I would 
even have noticed the noise on 40 meters ever at my house.

I have reduced the noise on the astron my adding a couple by pass caps, 
getting a solid ground separate from teh power leads, and using ferrites 
in the 12 volt leads to force the rf currents into the ground wire to 
the rig.

My conclusion: If you are really worried about weak signals use a linear 
supply with a good old heavy transfomer, or a marine battery. If you 
must use the switcher expect to spend a bit of time cleaning it up if 
you are in real low noise environments. For casual opearation in most 
circumstances I find the Astron to work fine. Even the cheaper model 
probably would be OK but you might have to do a bit of 
filtering/bypassing to really clean it up.

Brian / n6iz / 3d2izjim danehy wrote: