[TenTec] Radio Shack 25 amp switching supply?

[Gary Hoffman]

Hasn't anyone tried to ground/shield/filter these things ?  We used them at
the place I used to work, and I got them quieted down to the point where I
couldn't measure any noise with a scope hooked directly to the output of the
supply.

73 de Gary, AA2IZ


----- Original Message -----
From: <al_lorona at agilent.com>
To: <tentec at contesting.com>
Sent: Monday, March 10, 2003 4:17 PM
Subject: RE: [TenTec] Radio Shack 25 amp switching supply?


>
> I have posted on this topic here before. You may cringe at such a blanket
statement, but *all* switching mode power supplies generate noise. As users
of extremely sensitive RF receiving equipment, we must be prepared to
tolerate at least a small amount of RFI from these devices. Show me any SMPS
of any size from any manufacturer and give me a good receiver, and I will
let you hear the noise coming out of the supply. It's just a fact of life.
>
> The noise you hear will be greater with unbalanced antenna systems nearer
the SMPS. Operate from a hotel room with a random wire and an SMPS one of
these days and you'll see what I mean.
>
> The advantages of a SMPS are small size and light weight, but the
advantages of a linear power supply are its quiet-- if not nonexistent-- RFI
spectrum.
>
>
>
> > -----Original Message-----
> > From: Paul Christensen, Esq. [mailto:w9ac at arrl.net]
> > Sent: Sunday, 09 March 2003 8:18 AM
> > To: tentec at contesting.com
> > Subject: Re: [TenTec] Radio Shack 25 amp switching supply?
> >
> >
> > > Mine is going back to the store today.  If I lived in a
> > place where the
> > > noise level was always S5 to S8 it would be fine, but it is
> > not the case
> > > at this QTH.  I hear the noise on 20 meters, now, since the band is
> > > mostly quiet this morning.  Give me back my linear supply.
> >
> > I generally stay far away from switching power supplies: My main shack
> > supply is centered around an Astron RS-35 linear supply and power is
> > distributed to many devices via a RigRunner DC distribution
> > panel (which
> > btw, is a fantastic product).
> >
> > However, about a year ago, I was looking for a lightweight
> > supply that could
> > handle my Triton IV at full 100W output power for portable
> > operation.   I
> > sheepishly purchased the Astron SS-25 after reading a QST
> > product review of
> > a similar Astron SS supply.
> > As I recall, there was essentially no measured noise from the
> > Astron SS.
> >
> > The SS-25 is very light in weight, takes up a relatively
> > small footprint and
> > doesn't even blush when pushed to 25 amps over extended
> > periods of time.
> > There's a small thermostatically-engaged whisper fan on the
> > rear panel that
> > produces nearly no audible noise.  I absolutely love the
> > Astron SS amp.
> > However, I still would not consider it for the main station
> > where I leave
> > the RS-35 linear supply on 24/7.  I simply never want to have
> > to consider
> > whether or not a spur that I'm hearing is being generated by
> > the supply.
> > It's difficult enough in trying to localize shack noise
> > problems without
> > having to examine the supply and rule that out as a potential
> > noise source.
> > But for intermittent and portable operation, I couldn't be
> > more pleased with
> > the Astron SS.
> >
> > Also, Ten Tec makes some nice switching supplies and I would
> > bet that theirs
> > is at least as clean as the Astron.  I know in my previous
> > dealings with Ten
> > Tec, that they have been very sensitive to the user's power supply and
> > potential noise generation.
> >
> > -Paul, W9AC
> >
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> > TenTec at contesting.com
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> >
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