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Can I get away with using a 20 MHz oscilloscope to satisfactorily view video waveforms?

I know that in order to trigger all the test signals properly, I should use at least a 150 MHz unit -- preferably a conventional video waveform monitor. However, I cannot afford one.

It is not my intention to measure rise times or verify parameters in a professional capacity. Rather, I want to accomplish such simple things as verifying that closed captioning is present in the correct vertical interval line, determining that color burst and sync levels are "in the ballpark," and checking for the presence of SCH frame-burst signals.

To reiterate, I will be using the scope too infrequently to justify a major expenditure of funds, yet I want one with a bandwidth sufficient enough to allow me to count the lines in the vertical interval and identify what is in them.

Reply to
Cinderlane Productions
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Video waveforms are complex beasties. That's why you have waveform monitors. Even regular oscilloscopes need specially-configured triggering to make sense out of them. That's why you see such features as 'Video triggering' called out in the spec sheets on some models.

As for affording a waveform monitor, I've seen them for under $50 in some cases. Check Ebay. Check with whatever ham radio club is local to you for close-in electronics-dedicated swap meets. Check with used test equipment dealers. Check with pro-video editing places. Someone's bound to have an older Tektronix unit that you can get for cheap.

In other words, scrounge like mad, and don't give up. It may take a while, but I'll bet you'll find something.

Hate to break this to you, but I don't see any way that you can determine all the above WITHOUT a true waveform monitor. Heck, at that level, you may even need a vectorscope as well.

Happy hunting.

--
Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute.
(Known to some as Bruce Lane, ARS KC7GR, 
kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com
"If Salvador Dali had owned a computer, would it have been equipped
with surreal ports?"
Reply to
Dr. Anton T. Squeegee

Depends on just what you mean by a "video waveform"; so the answer is, "possibly."

If you have access to "baseband video" (i.e., it's not on a VHF or higher carrier) and we're talking about standard analog TV here (and not high-res PC video), then - sure, why not? There's not a thing in that signal that goes above about 5 MHz. But where you're going to get in trouble is most likely in the triggering and delay features - I doubt that a simple 20 MHz scope, unless it was originally intended for such work, is going to have what it takes to easily, say, isolate the vertical blanking interval and so forth.

Bob M.

Reply to
Bob Myers

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