Newsgroups: comp.sys.amiga.games
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!batcomputer!cornell!johnhlee
From: johnhlee@CS.Cornell.EDU (John H. Lee)
Subject: Re: Why don't European consider NTSC?
Message-ID: <1991Apr12.192748.9493@cs.cornell.edu>
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Reply-To: johnhlee@cs.cornell.edu (John H. Lee)
Organization: Cornell Univ. CS Dept, Ithaca NY 14853
References: <1991Apr05.194113.4449@disk.uucp> <1991Apr9.134755.11319@vaxa.strath.ac.uk> <2341@pdxgate.UUCP>
Date: Fri, 12 Apr 1991 19:27:48 GMT
Lines: 36

In article <2341@pdxgate.UUCP> algoa@eecs.cs.pdx.edu (Gregory Bowers) writes:
>cabp10@vaxa.strath.ac.uk (Dan Dare) writes:
>I haven't seen a real PAL screen for about 4 years, but I don't remember
>any more flicker than NTSC. Anyone seeing PAL on an NTSC Amiga isn't
>seeing real PAL. I don't know if it makes any difference, but the PAL
>scan rate is 50Hz, but the NTSC monitor should be 60Hz. Anyway, remember,
>most PAL countries have a 50Hz power supply, as opposed to 60Hz in North
>America, so maybe a 60Hz PAL in Europe would be impractical.
>
>If anyone REALLY knows for sure, please follow on.

	PAL's 50Hz flicker is very real to people who are accustomed to
60Hz refresh.  When I was in Europe last summer, the flicker was *very*
noticeable.  However, I suspect that as time passes I would have gotten
used to it and eventually would not noticed it at all.

	The reason for the differing scan rates *is* tied to the power
supply frequency, but not because it's impossible to operate a 60Hz
monitor on 50Hz power and vice-versa.  The PAL and NTSC video standards
were designed to minimize interference between the power supply and video
refresh.  If the two are not perfectly at the same frequency, a visible
(and very annoying) "hum bar" travels up or down the screen at the
frequency that is the difference between the power supply and video
refresh rates.

	At the time the standards were developed, it was nearly impossible
and very expensive to adequately filter out this interference.  Even
today, it's hard to design a non-video-rate monitor with a ripple-less
power supply and sufficient shielding to prevent this "hum bar".  You can
still faintly see this effect on many computer monitors as a slight
"wavering" that moves up or down the screen slowly.

-------------------------------------------------------------------------------
The DiskDoctor threatens the crew!  Next time on AmigaDos: The Next Generation.
	John Lee		Internet: johnhlee@cs.cornell.edu
The above opinions of those of the user, and not of this machine.