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Custom Installers' Lounge Forum - View Post
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The following page was printed from RemoteCentral.com:
Topic: | Video balun specs This thread has 5 replies. Displaying all posts. |
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Post 1 made on Sunday December 14, 2003 at 08:24 |
deb1919 Founding Member |
Joined: Posts: | September 2001 344 |
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Anyone have a schematic and parts list for making a composite video balun?
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Post 2 made on Tuesday December 16, 2003 at 03:38 |
Ernie Bornn-Gilman Yes, That Ernie! |
Joined: Posts: | December 2001 30,104 |
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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.
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A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw |
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Post 3 made on Thursday December 18, 2003 at 00:16 |
ZoneOne Founding Member |
Joined: Posts: | April 2002 24 |
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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
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OP | Post 4 made on Friday December 19, 2003 at 06:52 |
deb1919 Founding Member |
Joined: Posts: | September 2001 344 |
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DOug, you couldn't seriously be thinking of spending Saturday making one of these $15 items, could you? 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
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Post 5 made on Friday December 19, 2003 at 21:34 |
ZoneOne Founding Member |
Joined: Posts: | April 2002 24 |
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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
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Post 6 made on Friday December 19, 2003 at 21:46 |
geraldb Long Time Member |
Joined: Posts: | June 2002 412 |
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time is money! hobbies on the other hand can be a different story.
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