Here's what I posted to the Elecraft list in response to the same question.
= = = = =
On 5/18/2020 11:38 AM, Josh Fiden wrote:
> These SS-30M supplies have been around a long time. Do others report
RFI problems?
Josh, Bob, and all,
I have no experience with Astron SMPS, and have seen nothing. I do,
however, own several no-name switchers advertised as quiet that are
quite noisy.
My question was techie-rhetorical. We should not trust ANY reports that
xxx product is RF quiet unless we know a LOT about proximity of noise
source to antennas, the sum all of the other noise that could be
obscuring it in the observer's receiver, and that info for ALL ham bands.
A meaningful test would be waterfall plots from an SDR with a small loop
antenna that can be placed in proximity to the potential noise source.
This doesn't require lab-quality testing, simply a waterfall covering
the frequency range of interest. Prior to the availability of
inexpensive SDR RX, I've used (and still do for some applications) the
broad coverage RX in my VHF/UHF talkie.
= = = = = =
This post on the Elecraft list from K9FD says it better than I did.
73, Jim K9YC
-------- Forwarded Message --------
Subject: Re: [Elecraft] New Astron Switching PS RFI?
Date: Mon, 18 May 2020 08:51:25 -1000
From: K9FD <merv.k9fd@gmail.com>
To: elecraft@mailman.qth.net
I had two of them and both had RFI, on 12 meter band, it was a
broadband noise of
S2 or so. If your noise level is higher than S3 then you may not even
notice it as it
was noise similar to the noise floor, as wide as the band.
Had other "spots" on other bands that had hash but not too bad.
Have tried many switchers and every one I have had put noise someplace,
if you mention
that on this reflector all you get is a tirade of people with S5 to S6
band noise levels
screaming they hear nothing, they are correct they hear nothing.
Elecraft even admits the switcher they sell has noise.
I have a very very low external noise level at this QTH, so linear
supplies are the only way
I am sure to be free of noise, birdies, and crap internally. YMMV
Merv K9FD
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