Injecting digits into a analog video feed?

I need to put some digital iinfo, from a fast uart, possibly,maybe biohase mark, into a few lines of video blanking, on a standard 75R coax. 2 or 3 bytes per line will be ok

I was thinking of just using a simple PNP current source, from a

5Vish rail, fed from a micro, 8051 or similar.

I'll have an Elantec sync stripper doing a lot of the hard work/ timing, somewhere in the system.

Any gotchas on feeding a coax this way?

Martin

Reply to
Martin Griffith
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None other than possibly the transmitter and/or receiver may not like the DC component, or the DC is blocked and the threshold shifts.

Reply to
Fred Bloggs

Surely there's some kind of buffer driving the cable? It'd probably be better to insert the encoding there.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Look at how broadcast stations insert the time of day information into the video.

Tam

Reply to
Tam/WB2TT

I agree, it would be so easy to add the signal to the video buffer, but it's basically an add on, to add telemetry, by using a bnc T piece to insert the signal as a switched constant current, and my Tek/grass valley manuals are long lost

Martin

Reply to
Martin Griffith

No, that method was used in a lot of the cheaper analog broadcast equipment. There's a lot of good stuff about video here:

formatting link

You can download past editions free, but unfortunately there's no article index on the website. There might be one on the DVD.

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John B
Reply to
John B

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