Sean, small BW TV's don't do anything about rejecting color, but they do
reject it because they usually do not have the bandwidth to display it,
either in the IF or in the video amplifier sections. Professional monitors
do have rejection circuitry and the bandwidth and when the former does not
work then the color signal manifests itself in a very peculiar disturbance
pattern on the monitor (you can tell immediately what is on).

The reverse is also true, high resolution color images rendered on a
monitor while using composite video signal (CVBS) can have image details
that are b/w appear in color on a monitor because their features generate
color carrier frequencies in the Y channel.

So the way to get rid of color is to use a simple tank circuit (LCR) tuned
to 3.57 MHz (in America), with a 6dB bandwidth of about 350 kHz (which is
about 10% of Fo). However due to the items detailed above, you also need
to limit the bandwidth of the video signal before comparing, to lower than
3.57-(0.35/2) MHz.

The best way is, to modify the source of video signal so it does not
output color or burst at all. Then you have all the bandwidth and no
filtering problems. This is trivial in most cases (find the YC mixer in
the camera or VCR and remove the color signal coupling capacitor - this
works in most cases). TV tuners can be tuned 'low'. This puts the color
signal on the high attenuation upper slope of the SAW filter and will
remove color (and possibly sound in single IF TV tuner/if units). Use the
AFC control to do this on an assembled set.

good luck,

Peter

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