Video feed to Analogue R&S TV TX

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Video feed to Analogue R&S TV TX

Post by maarkotech » Wed Feb 04, 2015 6:39 am

Please can anybody help with this, i feed video & audio signals from a panasonic AV mixer to an image engine then from the image engine to the TX in analogue format, but i have been battling with HUMs on the tv video ouput. i have tried in taking power all from one UPS, i have shorten the distance between the Mixer and the TX as much as possible, still the HUMs on the video is still there, recently i also use Kramer isolation transformer it only reduced hums a little. please what should i use to get over this ground loops. kindly help

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Re: Video feed to Analogue R&S TV TX

Post by PID_Stop » Wed Feb 04, 2015 1:55 pm

If the problem is in fact a ground loop between your originating equipment and the transmitter, you might try inserting a video amplifier with a differential input at the transmitter end of the line. Since Kramer seems to be readily available to you, their model 104LN would be a candidate.

Ordinary video amplifiers tie the input connector's shield directly to circuit ground; a differential input lets the input shield float, and the input stage effectively subtracts the shield voltage from the center pin voltage. The result is that even fairly large amounts of common mode voltage (which cause ground loops in the first place) get cancelled out.

One other thing to check first, though: make sure the video coming out of your Panasonic and image engine don't already have hum in the video -- which could be the result of a bad filter capacitor in either device, for example.


-- Jeff

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