problem with Composite video signal

Hello to everyone, I am a new member and I think this is the best place to ask my question.

I have a mini camera that outputs composite video. when I conect it directly to the AV socket on the TV it works perfectly. However I want to send it across a wireless system. The system I am using is called the Airwave 5.8GHz modules (data sheets here http://www.dpcav.com/xcart/home.php?cat=249).

when I connect it to the system the composite video output is all messed up. It is moving allong the screen and is in black and white. If there is low light it will stabilise and show the image in a green colour. I have looked at the ocilisscope traces at both ends of transmission and the output is missing a portion from the bottom which i think is the sync of the signal, and that is there when it’s being trnsmitted. Somewhere in transmission that sync signal gets cut off. (the system is compatible with NTSC and PAL)

Any ideas would be great. Thanks very much

Not exactly the most relevant forum for your problem. :stuck_out_tongue:

I’d try a known good source like a VCR.
If it also has problems then its the transmitter.

Hussy11,

Do you have a pic of the scope measure? Take one from camera out connected and other disconnected, and another from receiver video out, connected and disconnected from monitor.

Are you using a simple TV or a video monitor?

The Airwave datasheet says that video input of transmitter must have 1Vpp (1 volt peak to peak). Is your camera video out 1Vpp? If higher, it can deform video, and levels are important, since sync and video have separate portions in levels. If deformed, receiver cannot recover it.

And the impedance is important too. Airwave is 75ohms, and you must check camera and TV/Monitor impedance. If you’re using a monitor, is it 75ohms charged on loop connector?

Another thing you must try is video without audio, because higher audio levels on transmitter input can make noise that could affect video signal on transmission.

Did you connected all components shown in datasheet?

Is your power source regulated?

Did you try with more than one frequency? And are both (transmitter and receiver) at same frequency?

This images shows video portions (color bar test pattern), so you can analyse if is the sync that is not correct.

Note that scale is not in volts, but in IRE. video portion is 0 to 100 IRE. sync portion is 0 to -40 IRE. Your Osciloscope will show it in volts scale.

Thanks for your reply Adilson Akashi. You were right about the voltage level of the input signal, it was too large. I tried to reduce it using a potential divider circuit with two small resistors, that worked and now it is sending the signal through the airwave’s. The set up of the rest of the system was all ok. Thanks again!