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KB2VXA > CURE 04.05.03 19:54l 38 Lines 1615 Bytes #999 (0) @ WW
BID : 6826_WT3V
Read: DB0FHN GUEST
Subj: Re: VK5QX & switching PSUs
Path: DB0FHN<DB0ZWI<DB0HDF<DB0ERF<DB0MRW<DB0RGB<OK0PPL<RZ6HXA<SP7MGD<WB0TAX<
KB2TXP<KB2FAF<WB2VPY<WA3LWR<W2LV<KB2VLX<KC2COJ<WT3V
Sent: 030429/0431Z @:WT3V.#CNJ.NJ.USA.NOAM #:6826 [Lakehurst] $:6826_WT3V
From: KB2VXA@WT3V.#CNJ.NJ.USA.NOAM
To : CURE@WW
Hello Ian and all,
You are quite correct about PSUs in the USA, never seen a linear supply
in even the rather early PCs. The only place I have seen big chunks of
iron and pass transistors was in mainframes back in the 60s and 70s. They
were large, heavy things usually made by Lambda and put out up to 100
amps. I'm using one of the smaller (12V @ 20A) here in the shack, but the
thing to remember is they were designed with forced air cooling in mind.
On the subject of RF noise. another thing to remember is that the greater
bulk of it is radiated from the case rather than conducted. The output of
the PSU is carefully filtered using common mode chokes and must be
absolutely pure to avoid disruption of the data. Even the slight ESD
created by moving a data cable can "crash" a computer, I found out the
hard way while working around an industrial mainframe. In the case of
radiated noise nothing can be done short of rebuilding the PSU and
nothing is guaranteed.
Of course the label says something to the effect of "Complies to part
(something) computing device." but that is along the lines of low power
transmitting devices and as we all know means a certain signal level at
1000 feet from the source. This means you can flood the neighborhood with
hash and it's still legal.
After reading various comments on the subject, I have likely drawn the
same conclusion as most, work off the battery or another power source
that is noise free.
73 de Warren, KB2VXA @ WT3V-4
e-mail: kb2vxa@juno.com
Message timed: 04:36 on 2003-Apr-29 GMT
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