Extending CCTV Camera Over a CAT5 Cable

I don't think that would work too well, you would probably have a lot of interference on the video and audio, but if you use baluns to convert the signal, you can use your cat5 cable (up to 1000ft/300m they say) and get good results. The baluns are basically a transformer that changes the signal impedance so that's it's not susceptible to noise. The one linked here also does the audio and power:

link

I found that one very quickly with a search for "CCTV over CAT5", so look around and find one that meets your needs and your budget. I suppose it wouldn't hurt to try your experiment first, without the baluns, as long as you have the time. It might just work OK since you are dealing with a short distance.

Your other choice is to just use an "extension cable", they are very common too for distances up to 100ft/30m, here's one for under $20 shipped:

link

Hope that helps.

Tom D.

"Would there be a massive quality loss... ?" - Probably. Cat5 cable has 100Ω characteristic impedance, while CCTV co-ax is usually 75Ω, so that wouldn't help. It would also depend what the local electromagnetic environment is like and how noisy the 9V PSU is. Give it a try, and let us know how it goes.

The balun thing that you linked to is not what I am looking for. It has to use an rca connection. One for video and one for audio. The connection on the device you linked to looks like coaxial.

If you do a quick search, you will see that there are a variety of products offered. I saw some that had BNC, some had RCA, and one set I saw had the cables terminated to BNC, but came with BNC to RCA adapters, so they cover the full range of setups. I think for your distance, the extension cable would be the best solution, unless the area for your cable run is not easily accessible, and your CAT5 is already in place.

Tom D.

BTW - If the best/cheapest solution has BNC connectors, you can buy BNC to RCA adapters for less than $1/each.

So these BNC baluns are just carrying normal composite video? And not RF video like that which is picked up by a tv aerial?

Yes, they "convert" the signals so to speak, by using a transformer(s) to match the source and load impedances. In this case, they are matching the composite video and audio signal to the characteristics of CAT5 cable. Then, at the other end, they reverse the process, and you get your composite video and audio output. The DC supply voltage for the camera is easier to deal with, no conversion or matching is needed for that.

Sorry for the long-winded explanation, the short answer to your question is "yes", the devices I linked to is intended to carry normal composite video. But keep in mind, per my explanation above, you need two of them, one on each end of the CAT5 cable.

Tom D.

Thanks for all the info. Do these baluns take any power from the power cable or are they just passive? And why do they not have normal rca connections?

They're passive - like transformers.

Would it be possible to build a video balun with a toroidal transformer or is there other more advanced circuitry in there as well?

Theoretically possible, but for the price, I don't think it's worth it. There's a lot to consider, and if you just happen to have a toroid laying around, the chances are it's not the best one for the job. There are probably two baluns at each end of these; one for audio and another for video, probably not too much in the way of other circuitry, all the "magic" happens in the balun and it's windings.

The RCA vs BNC is a matter of choice. Some equipment comes with BNC, some with RCA, that's why you see both styles for sale, and some makers that sell the adapters with the units.

Tom D.

I cant be bothered buying adapters so I will cut the BNC connectors off and solder on composite ones. Heres the one that I bought http://www.ebay.co.uk/itm/320714025714?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Well, on the one end, the BNC is built into the enclosure, how are you going to cut that one off? It looks like you are in the UK, if you are in a larger residential area, you should be able to find an adapter for around $1 at the UK equivalent of Radio Shack? Anyhow, looks like you got a good deal on them.

Tom D.

I could take apart the balun and solder in a composite connection.

If you look at the same site where you purchased the balun set, they have the adapters you want at £1.95 for 4 pieces shipped. It looks like you would have also received a shipping discount if they could have shipped all the items together.

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For 20m you can probably get away with it, assuming the 9V is DC and that you're not running near an electro-magnetic field source like a fluorescent light fixture. I've done similar cheats before with short cat5 runs. If you run any AC power in the same cable, forget it.

Standard runs for audio and composite video call for twisted shielded pair, but the twist on cat5 is so tight it helps prevent induced interference. You must use a twisted pair (not just "2 wires") of the cat5 for each function. Any induction goes into both wires equally and in the same direction along the pair. That means that the induced signal in each wire has opposite polarity to the other half of the circuit loop (one wire is "going out" the other is "coming in"), so the 2 induced signals cancel each other out.

Grounding the spares probably won't help since they are not wrapped around the other pairs. If you do ground them, only connect on one end and insulate the opposite end of the wires from ground and from each other.

I have sent composite video through a cat5 cable without baluns and the video only loses a tiny bit of quality. I also attached a condenser microphone capsule to the cable and the audio works well too. I bought the baluns just in case I want to have a camera in my shed which is about 30m from the house. Can cat5 cable be buried without the cable being damaged by moisture?

I'm not sure what the "type number" would be, but you would need a rating of "direct burial" in order for it to last any length of time. A standard CAT5 cable would work for a while. I would imagine that cable rated for burial will cost quite a bit more.

Tom D.