require suggestions for TV modulation modules

Hello,

Little Hello:
This is my first post here as I've only just found out about EDAboard, it's good to see such a wealth of design knowledge being shared.

Context:
I have a lot of video cameras (pal baseband video output) that are used around a theatre/church/stage for recording action. All are currently connected back to vision mixers by coaxial (RG59) BNC terminated cables. I would like to be able run fewer cables by employing a modulation scheme as is use by over the air TV and running one cable from the last camera in the chain, via the other cameras, to a demodulation box.

Problem:
The part numbers and suppliers for the modulator modules I've seen listed on the internet (even ePanorama) are all out of date and no longer in production.

Detail/Spec of part required:
Module has to be currently in production and available to an amatur/experimenter (i.e. not just 1000 unit sales).
I2C control of frequency choice
RF in and out ports such that they can be chained
Basically, I would like the same module as the ones I can see in my VCR
I don't really care about audio


I hope I've been clear and someone can help me.
Thanks,
Alan G

Hello Alan,

You'll find some simple VCR type modulators on the below web page.

**broken link removed**

They are in production, and you could buy smaller quantities (I buy usually 100 pcs once. If you need more info about the purchase, contact me by PM)

I also have a similar project you described, so I recomend to take care about the following issues:
-the output frequency range of these modulators is (usually) in the 470-860 MHz range (UHF). There are some low frequency models, but if you want to chain them on a single coax you should use the UHF model.
- the output level is around 70 dBuV and the C/N typically 45 dB , which is acceptable for connection to a TV set with a 1-2 meter long coax cable. But for connecting them with several 10 meters it is not enough. It will degrade your C/N.
So, you should first use an amplifier, and after that connect through a directional coupler to the common coaxial cable (this one should be RG6 at least, due the higher loss at UHF of the RG59).
- if those above looks too complicated, you still can made your own modulator using for example a TDA8822 and a few passive components. You can program the output frequency on I2C.

Best regards,

Al