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:
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