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From: rwa@cs.athabascau.ca (Ross Alexander)
Newsgroups: comp.sys.atari.st
Subject: RFI, the FCC, and STs (was re: Talking about other computers here)
Message-ID: <479@aupair.cs.athabascau.ca>
Date: 6 Dec 90 18:20:16 GMT
References: <1990Dec02.215601.7327@ecst.csuchico.edu> <1990Dec3.153120.27313@cunixf.cc.columbia.edu> <1990Dec3.173941.29280@cs.ucla.edu> <1990Dec3.195756.27537@cunixf.cc.columbia.edu>
Organization: Athabasca University
Lines: 56

cmm1@cunixa.cc.columbia.edu (Christopher M Mauritz) writes:
>just pointing out that Atari has pulled the FCC-is-holding-us-up stunt
>so many times in the past that maybe (just maybe) the fault lies at
>Atari.  How many times can you tell your teacher that your dog ate your
>homework without finally taking the blame for not doing it? :-)
>Besides, even the stuff that did pass must've been marginal.  My old
>1040ST used to create snow on any TV I was watching in the same room.
>Of course, matters didn't get much better when I removed the RF shielding
>to make room for my RAM expansion board. :-)

I can add a few things here.  I have an old 1040st, and a few
peripherals for it (SCSI disk, printer, modem).  I also have an
AT&T 6300, a rather doddering PC-clone machine; it has an internal 30
meg drive.

I am particularly concious of RFI [radio frequency interference]
because, as a radio amateur I am constantly running both radios and
computers in close proximity.  For those who are interested, the
application is amateur packet radio networking, a very interesting mix
of two technical hobbies :-).  But I digress.

In short, the 1040st howls all up and down the bands.  We're talking
continuous S9+20dB heterodynes and growlies from baseband all the way
up to 450 MHz (to be charitable, it does fall off somewhat in the UHF
bands. On 145.01 MHz it's still pretty damned loud).  How this thing
ever got past the FCC I can't begin to imagine.  I can only assume
Part 15 subpart J class B means "leaks RF like a sieve".  It took
fairly heroic measures to get the intereference down to the point
where I could recieve anything from other stations; lots of bypassing,
coax cables, chokes, shielding, and physical separation were needed.
Having done all that it works fine (good serial I/O, lotsa horsepower
:-).

Now in contrast, the pc6300 is _silent_.  A little rumble on 75 metres
perhaps, but otherwise dead quiet straight out of the box.  A nice
steel chassis, bolted together quite thoroughly; chokes on all cables
running in or out.  Of course it's an 8086 abomination but at least it
isn't destroying all reception in a 30 metre radius!  And it's only
certified to class B.  Most strange.

The thing that really puts the cap on this, however, is the ds2100
that I am pounding this note in via.  16MHz risc box (mips engine), 12
Megs of ram, a whole raft of externally cabled SCSI devices, ethernet
connections, a mouse, a 1000 x 900 display, oceans of transistors all
frantically switching, right?  And it has a class A certification,
which is even more relaxed than the class B of machines intended for
home use.

And yet, and yet, it's almost as quiet on 2 metres (~ 146 MHz) as the
pc6300.  What exactly is Atari doing wrong, and why are their machines
so noisy?  Corner-shaving and cost cutting have limits, y'know.

Yours for RF sanity,
-- 
--
Ross Alexander    rwa@cs.athabascau.ca    (403) 675 6311    ve6pdq