Jumpy [B&W] composite video signal from 1974 dumb terminal

[ppppenguin]

What a revolting video waveform. at 10us/cm the H sync pulses are OK-ish but there's loads of other stuff hanging down below black level during th active lines. It would be a miracle if anything locked to that.

Actually chroma information can go below black but that doesn't look like chroma to me.

[zeno]

This may help you
https://www.ni.com/en-us/innovations...video-101.html

Everything I have noticed ran on 1V P-P ( after the video detector). I
cant say for sure on all monitors, there are different schemes. The second
higher signal may be sync. BTW tradition is to show two complete cycles
( lines ) thats what we are used to seeing.
Good luck

73 Zeno
LFOD !