Quiet? Not the FCC Class B telecom units I've been playing with. These
beasts put out relatively low noise differentially between output V and its
ground but put out a lot of noise "common mode" between the output pair and
the case (green wire ground), between the input leads and case, and between
the input return and output return.
I've been measuring these things at work and currently see 2V peak to peak
impulses at the 75 KHz switching frequency followed by 10-20 cycle of
ringing at about 50-100 MHz.
>From what I can tell, the manufacturers pass FCC EMI testing by putting a
resistive load on the outputs that's not connected to anything, just
resistors floating in air. This minimizes the tendancy for the output
ground noise to pump back into the input lines. But once we connect the
outputs to our equipment (and it's chassis ground), the input conducted
noise rises by 20-30 dB and we that far out of spec.
jeff, wa1hco
----- Original Message -----
From: "Steve Katz" <stevek@jmr.com>
To: "'Phil Levin W2GE'" <w2ge@arrl.net>; <Amps@contesting.com>
Sent: Monday, April 01, 2002 6:27 PM
Subject: RE: [Amps] Re: 12V 120A Switching Power supply?
>
>
> > Uh.... Did not know that!
> >
> > Curiously, How much does one of these 120 amp switchers cost and are
> > they RF quiet?
>
> ::Like most modern switch mode power supplies in the 500W+ class,
> they run about a dollar per Watt. I would say they are _very_ RF quiet,
> since their primary applications are powering large telecommunications
> systems which need to meet not only FCC Part 15 Class (B) but also Part 68
> and a variety of other certification requirements. We use 'em all the
time.
>
> 73 de Steve, WB2WIK/6
>
>
>
> > Phil W2GE
> >
> > -----Original Message-----
> > From: amps-admin@contesting.com [mailto:amps-admin@contesting.com] On
> > Behalf Of Steve Katz
> > Sent: Monday, April 01, 2002 6:10 PM
> > To: 'Doc Johnson'; amps@contesting.com
> > Subject: RE: [Amps] Re: 12V 120A Switching Power supply?
> >
> > There's been a great deal of speculation and advice on here regarding
> > this,
> > but in reality, a simple answer to the simple question has been
> > provided.
> > There are absolutely 12V, 120A "off the shelf" power supplies readily
> > available and currently for sale. If someone wants one delivered
> > tomorrow,
> > he could have it.
> >
> > The MagneTek MG3 product is one I've used for a few years now, in
> > exactly
> > this category. Delivery is a few days or less, and it's a solid,
> > certified
> > product. Not large or heavy, and a twin MG3 pack provides 12V regulated
> > at
> > 200A continuously. There's a 48v version of the same product.
> >
> > Unipower, TDI, NMB, Todd and others make similar stuff. Nothing unusual
> > about the requirement at all, although evidently the ham community seems
> > to
> > think so...
> >
> > WB2WIK/6
> >
> > "Each success only buys an admission ticket to a more difficult
> > problem." --
> > Henry Kissinger
> >
> > > -----Original Message-----
> > > From: Doc Johnson [SMTP:bluescreen@comcast.net]
> > > Sent: Monday, April 01, 2002 2:42 PM
> > > To: amps@contesting.com
> > > Subject: [Amps] Re: 12V 120A Switching Power supply?
> > >
> > > Why not build the amp out of 48 volt transistors? I have a dozen 300
> > watt
> > > 48 volt power transistors that I have been saving for such a project.
> > This
> > >
> > > should reduce the current requirements and hopefully make the power
> > supply
> > >
> > > lighter?
> > >
> > > _______________________________________________
> > > Amps mailing list
> > > Amps@contesting.com
> > > http://lists.contesting.com/mailman/listinfo/amps
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> > Amps mailing list
> > Amps@contesting.com
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