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Author Topic: How to Measure NTSC Composite Video Bandwidth Loss, Long Cable Run  (Read 1034 times)

Dave Gunnell

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Hi All:

I am fixing a video problem at a local church.  The original CATV installer ran at least 250+ feet of RG-59 coax for a composite video line to a room at the far end of the building.  While there is enough signal/bandwidth to support most TV monitors, the Sony projectors they have will not sync to the signal.  I believe the issue is primarily loss of high frequency bandwidth over the long run.  A small Kramer 101L video amp with EQ fixes the problem, but I don't know how to measure the receive end for the correct amount of level and EQ boost at the amplifier end.  While it works and looks fine, I would like to throw a little more precise science at the resolution.

So how is this usually done?  Would an inexpensive oscilloscope be helpful?  Is there anything that a video test source (such as the BK Precision Model 1257 NTSC Pattern Generator) would help with?  What about video calibration DVDs, such as this one?  Can they be used to "eyeball" the video amplifier EQ tilt?

Ultimately I would like to purchase equipment so I can measure the line loss and HF attenuation in these situations, just not sure how this is typically done in the field.

Thanks for your help.


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