Video over CAT5

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bh00

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Hi,

I've searched to find a simple circuit diagram that'd allow me to send PAL composite or svideo signals over simple UTP Cat5 cable. Can anyone point me in the direction of an appropriate circuit? Ideally it'd be some sort of simple active balun device to do the conversion with as little loss as possible. The actual cable length is only going to be 30-40m anyway. I'm also interested in a way of sending unbalanced stereo audio over cat5 as well if anyone has diagrams for that.

Thanks,
Ben
 
We send composite video over CAT5 at the TV station i work at. The circuit looks VERY simple. Since SVID is prety much composite, then it should work the same way. There really isn't a "Circuit" for it, it is just as simple as connecting each end of the wires to it's original spot on the connectors.
 
EL5177 and EL5175 are designed to drive and receive video over twisted pair.
 
Sending unbalanced audio over an unshielded pair is asking for lots of hum, unless you are in the middle of nowhere and there isn't any mains wiring nor light dimmers nearby.
 
audioguru said:
Sending unbalanced audio over an unshielded pair is asking for lots of hum, unless you are in the middle of nowhere and there isn't any mains wiring nor light dimmers nearby.
Click to expand...
Is there a set of simple ICs that could be used to balance the signal and then return it to how it was at the other end? Would some sort of RS485 transciever work?
 
Yeah sorry I was looking into those but I got the impression they only worked for video. Plus the only option I can find them in is some sort of small surface mount package which I was trying to avoid.

Does anyone know what kind of components are used in the kat5 system?

Thanks
 
OK, here's a video driver and receiver that I ginned up. I simulated it, and in the sim it is flat within 0.1dB out to 5MHz, with -3dB bandwidth of about 32MHz. 30M of Cat-5 will be down about 1.5dB at 5MHz, so you may want to add a little equalization on one end. Post here if you think you need it.

Regarding audio: You could use the same circuit. The AD8055 is supposed to be fairly low noise, but you could do better for audio. Pick a good low-noise op amp, and scale the resistors up by a factor of 10 or so. Get rid of R1 and R15, unless you want to AC couple your audio in, in which case you can make R1=10k. You may also want to use higher supply voltages.

Analog devices has been good to me regarding samples. You might try getting the amplifiers that way.
 

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  • cat5 video dvr and rcvr.GIF
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About unbalanced stereo signal ..use a FM high freq signal. Just build a FM tx (see this **broken link removed** or use BA1404 ) and a demodulator circuit on the other side (FM rcvr).
About video ..hmm ..I'l go with Ron H's idea al thought the SMD package is a major problem.
U can use a similar metod with above..
 
The AD8055 is available in an 8 pin DIP (AD8055AN or AD8055ANZ).
 
Thanks guys, I'll order some of these chips and try breadbroading it. I was thinking maybe a LM833N would work for the audio version (plus as there's two in a package its less chip count) - does that look alright?
 
bh00 said:
Thanks guys, I'll order some of these chips and try breadbroading it. I was thinking maybe a LM833N would work for the audio version (plus as there's two in a package its less chip count) - does that look alright?
Click to expand...
LM833 looks OK.

When you build the breadboard, use a ground plane (video especially).

I forgot to mention that the gain of the driver is R3/R2. You might need less gain for the audio circuit if you eliminate the termination resistors, as I suggested.
 
Circuit help

Ron H,

Your circuit seems to be what i am looking for. I have a basic knowledge of electronics and just wanted to check a few finer points about the circuit that you desgined with you.

I want to send composite video over the cat 5 cable with RCA connectors. Could you please explain how i attach / couple the source into this circuit and also what do/are the VCC1/2 and VEE1/2 and v2,3,4,5 do? Am i right in assuming that the triangles is the symbol for the -ve/ ground?

thanks in advance

James
 
I drew the power supplies as batteries. You will need to provide +/-5 volts (vcc1/vee1) for the transmit side, and separate +/-5 volt supplies (vcc2/vee2) for the receiver, since it will presumably be located remotely from the transmit side. Presumably, you won't want to use batteries. If you need help with the power supplies, post your questions here.
 
thanks,

That makes more sense to me now. With the RCA type conncector, is it the peg which gets connected to the input and the outer circle connected to the ground/-ve?? Also do all the triangles indicate that compnent is connected to the -ve part of the power supply?

Thanks in advanced james
 
You are correct about the connectors.
Ground is a common node. The shield (outer circle) on your connectors, the negative pins on your +V power supplies, and the positive pins on your -V supplies should be connected to ground. For video, it would be advisable to have ground planes on your circuit boards. You do not need a connection between ground and earth.
 
Oh ok, I din't realise that. i just thought that the ground was the -ve part of the power supply and was unaware that there wasa a +5v which was separate to a -5v

Would i need to use a voltage regulating ic to make the 5 volt supply? I am still slightly confused about making the power supply with a +5v and a -5v as well as ground.
Do you have a power supply circuit that you have made im not sure wether i want to use mains or a 9v battery? Any suggestions would be appreciated

I was planning on making it on breadboard as i dont have facilities to make a pcb would the circuit still work????

Your input is greatly appreciated with this, i am nearly there in understanding.

James
 
A video amplifier should be made on a pcb or on stripboard. It would probably oscillate and pickup interference if a breadboard is used.
 
For video breadboards, I use perf board with plated-through holes on 0.1" centers, with ground plane on one side. As Audioguru said, you can also use stripboard.
The simplest power supplies would probably be made with a couple of 9 volt DC wall warts, and 78L05 regulators. The wall warts should be rated at at least 100mA each. See below.
 

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