Anyone have a schematic and parts list for making a composite video balun?

Huh?

You are starting with balanced video and converting it to unbalanced? Or the other way around? What equipment works that way?

Or do you need a transformer that passes a video signal, stays unbalanced, but isolates the grounds?

Because of its frequency response, the actual wire, core, and even style of winding are critical and would be pretty hard to reliably make at home.

On the other hand, assuming you literally mean balun (bal = balanced. un = unbalanced, so balun = balanced to unbalanced, such as a TV 300 to 75 ohm transformer), the parts list is one balanced connector, one unbalanced connector, two pieces of wire, and a proper magnetic core. Wind the wires around the core in a way that will keep the response flat from about 20 Hz to at least 6 mHz, and use a proportion of turns equivalent to the proportion of the characteristic impedances of your balanced and unbalanced lines.

You might need to add some small capacitors in one or more places to help shape the response. A video signal generator, a wide-band noise generator, an oscilloscope and a spectrum analyzer will help a lot. If you want to devote a couple more weeks to it, you can do this with only a sine wave signal generator and a scope. Don't forget to purchase ultra-low capacitance scope probes and precision loads, and to carefully control the source impedance of your signal generator from about DC to at least 6 mHz.

Or you could call a company that sells isolation transformers for video surveillance installations. Hopefully you really don't mean balun, as those are 1:1 transformers with unbalanced inputs and outputs.

I think deb means the video baluns that allow the various flavors of video to be sent over cat5. We have used both composite and S versions from MuxLabs and they work great.

What I can't figure out is why anyone would need a schematic for one! DOug, you couldn't seriously be thinking of spending Saturday making one of these $15 items, could you?

Andy

No, just curious if they're easy to make. And I'd love to know where to get them at that price.

How've you been, A?

- Doug

Doug,

Okay, okay, $15 was a little low. How about $17.95?

[Link: videocapturecard.com]

Of course that's our cost, it's only one end, and it is probably not MuxLab quality. But I still wouldn't make one!

If you recall we once tried that route when we got tired of paying for Niles AC-3's. 'We can make these for $10 worth of Radio Shack parts' was the call of the day. Didn't quite work out that way.

Regards,

Andy

time is money!
hobbies on the other hand can be a different story.