Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84 / ST 1.0; site saber.UUCP
Path: utzoo!linus!philabs!cmcl2!seismo!harvard!talcott!panda!genrad!decvax!decwrl!sun!idi!saber!skinner
From: skinner@saber.UUCP (Robert Skinner)
Newsgroups: net.wanted,net.video,net.micro
Subject: Re: Looking for a monitor
Message-ID: <1745@saber.UUCP>
Date: Mon, 19-Aug-85 20:26:54 EDT
Article-I.D.: saber.1745
Posted: Mon Aug 19 20:26:54 1985
Date-Received: Fri, 23-Aug-85 06:27:13 EDT
References: <414@sbcs.UUCP> <303@kitty.UUCP>
Distribution: net
Organization: Saber Technology, San Jose, CA
Lines: 50
Xref: linus net.wanted:6222 net.video:1328 net.micro:10327

> > We are on the market for a color monitor with the
> > following characteristics:
> > 	o  720 pixel x 400-600 line resolution.
> > 	o  60 Hz vert freq, ~28-40 Khz horiz freq, 40 Mhz BW.
> > 	o  12-14 inch diagonal measure screen, .31mm pitch phosphor.
> > 	o  Analog RGB input, need not be linear. Prefer ~1 Volt input.
> > 	o  Low cost (<$1600).
> > Any suggestions?
> 
> are no inexpensive raster scan color displays that will operate in that
> frequency range.  I know - I have looked!  The least expensive monitor I
> could find was a Conrac 7211RS19 which set us back about $ 3.9K a year ago.
> The 7211 gives 1080 horizontal by 809 vertical pixels for a 1225 line
> resolution.  That is more resolution than you asked for - and was also more
> than we required.  However, we had some graphics hardware that would *only*
> work at 31 KHz.
> 	There seems to be a whole order of magnitude price jump when one
> goes that high in horizontal scan rate.  I am not certain why that is, since
> the monitor circuitry is not that much more complex than that of NTSC monitors.

Here's a simple formula for the horizontal scan frequency required for
a given resolution:  
	(horiz. freq) = (vert. res.)x(refresh rate)x(1. + % scan interval)

This should be fairly obvious, the beam will trace a horizontal line
once for each vertical line, 60 or 30 times a second, plus a small
percentage to allow for vertical retrace time (5-10%).  So, what the
original poster needed was about 
	(400-600) x 60 x (1.05-1.10) =  25.2 - 39.6 KHz.

He will probably find something acceptable at about 31.5KHz, since
that is the RS-170 standard (2x NTSC).  I don't know the prices, but
I'm sure they aren't as high as $3.9K.  31.5KHz isn't that state of
the art, high res monitors have to support 60-80KHz.

As far as the second poster goes, How do you get 1225 lines out of a
monitor with 809 line resolution?  Besides, if I take your numbers and
solve the above equation for the refresh rate, I get less than 27Hz
(bad flicker).  I hate to say it, but I think Conrac sold you a bill
of goods.

------------------------------------------------------------------------------
			.. man then went on to prove that black was white, 
			and was promptly killed at the next zebra crossing.

Name:	Robert Skinner
Snail:	Saber Technology, 2381 Bering Drive, San Jose, California 95131
AT&T:	(408) 945-0518, or 945-9600 (mesg. only)
UUCP:	...{decvax,ucbvax}!decwrl!saber!skinner
	...{amd,ihnp4,ittvax}!saber!skinner