[TenTec] Radio Shack 25 amp switching supply?

Mon Mar 10 14:32:09 EST 2003

Hi, Scott,

In fact, I made a number of similar modifications to one of the Astron SS- family (like Paul's) after I got one about six years ago. I was not pleased with the RFI before the mods but afterward I considered the supply's performance acceptable, but not excellent.

Al  W6LX

> -----Original Message-----
> From: Scott Rosenfeld [N7JI] [mailto:ham at w3eax.umd.edu] 
> Sent: Monday, 10 March 2003 1:26 PM
> To: tentec at contesting.com
> Subject: RE: [TenTec] Radio Shack 25 amp switching supply?
> 
> 
> Not to mention that any device CAN be made nearly completely free of 
> emissions...by building a gaussian surface around it.  
> 
> Sure, you have to bond every panel to each adjacent panel, 
> but it can be 
> done.  Once this is done, the number of "holes" in the "shell" will 
> determine how much RF gets to the outside, as does how well 
> the "shell" is 
> grounded (to a true ground - remember, at RF, power ground <> earth 
> ground).
> 
> There is still the issue of conducted RF, carried on the output leads 
> and possibly on the input leads.  It seems to me that by putting an 
> RF choke on the input AND output as close to the supply as possible, 
> you're pretty much giving the RF energy nowhere to go without a its 
> putting up a serious fight.
> 
> That said, I have one of these RS supplies and will try out the RFI 
> suppression as soon as is practical.
> 
> On Mon, 10 Mar 2003 al_lorona at agilent.com wrote:
> 
> > 
> > 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
> > > 
> > > _______________________________________________
> > > TenTec mailing list
> > > TenTec at contesting.com
> > > http://lists.contesting.com/mailman/listinfo/tentec
> > > 
> > _______________________________________________
> > TenTec mailing list
> > TenTec at contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> > 
> 
> -- 
> 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 at w3eax.umd.edu  http://w3eax.umd.edu/~ham
> 
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
> 