SHEILDING! copper flashing, solder, etc.
On Mon, 10 Mar 2003, Robert & Linda McGraw K4TAX wrote:
> OK, that takes care of conducted noise on the output, now what about
> radiated noise? That is usually a significant part of the problem.
>
> 73
> Bob, K4TAX
>
> ----- Original Message -----
> From: "Gary Hoffman" <ghoffman@spacetech.com>
> To: <tentec@contesting.com>
> Sent: Monday, March 10, 2003 4:21 PM
> Subject: Re: [TenTec] Radio Shack 25 amp switching supply?
>
>
> > 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@agilent.com>
> > To: <tentec@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@arrl.net]
> > > > Sent: Sunday, 09 March 2003 8:18 AM
> > > > To: tentec@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@contesting.com
> > > > http://lists.contesting.com/mailman/listinfo/tentec
> > > >
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> > >
> >
> >
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> >
>
>
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--
Scott Rosenfeld ARS N7JI
541-684-9970 Eugene, OR Land o' much rain
If you find me on the air, I'm probably in my car
ham@w3eax.umd.edu http://w3eax.umd.edu/~ham
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