a real challange?

[old_tv_nut]

For RF input, a couple of millivolts up to a tenth of a volt should do. If the instructions say to set the contrast/gain to a certain fixed value, do that and adjust the input level up from zero until you get a few volts (2 to 4) out of the video detector. If you have information on what the usual video amplitude is out of the video detector, go for that instead.