Path: utzoo!attcan!uunet!husc6!mailrus!cornell!uw-beaver!fluke!ssc-vax!uvicctr!collinge
From: collinge@uvicctr.UUCP (Doug Collinge)
Newsgroups: comp.sys.atari.st
Subject: Re: Mono shakes
Message-ID: <461@uvicctr.UUCP>
Date: 5 Aug 88 17:54:30 GMT
References: <8808020007.AA19314@ucbvax.berkeley.edu>
Reply-To: collinge@uvicctr.UUCP (Doug Collinge)
Organization: University of Victoria, Victoria B.C. Canada
Lines: 36

In article <8808020007.AA19314@ucbvax.berkeley.edu> BRIGHT@DALAC.BITNET (BOB BRIGHT) writes:
>     So what was happening?  My guess is that the SM124 is pretty well
>shielded from RFI, but is quite sensitive to magnetic fields.  Maybe
>I'm wrong about this (could someone who knows more than I about such
>things please comment?), but there's no doubt that those invidious
>little heater fans were generating lots of RFI, and they didn't make a
>lot of difference unless they were right next to my monitor.  When the
>heaters were turned on, on the other hand, they were drawing
>considerably more current through the electrical service and meter,
>and this would increase the surrounding magnetic field considerably.

There's no particular reason why a monitor should be subject to RFI and
heaters don't make RFI, at least, not continuously.  Yes, your monitor
is sensitive to magnetic fields.  Monitors are.  The reason the mono
monitors seem more sensitive that others is because of the 70Hz refresh
rate: it beats at 10Hz with the 60Hz fluctuations in the magnetic
fields from all manner of stuff, especially cheap, leaky transformers 
("power rats", for e.g.).  Monitors that are operating at 60Hz will not
shake because the 60Hz is pretty well synchronized with the power line.
The monitor "crawls" instead, which is less noticable if the difference
in frequencies is small enough.

This is why TV's in North America operate at 60Hz and those in Europe at
50Hz.  What I'd like to know is how many people can see flicker on
colour TVs?  I can even see the flicker at 70Hz sometimes but others
say they can't.  I can't use a colour monitor comfortably because of
the flicker.

-- 
		Doug Collinge
		School of Music, University of Victoria,
		PO Box 1700, Victoria, B.C.,
		Canada,  V8W 2Y2  
		collinge@uvunix.BITNET
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