Security Camera Video and Power down the same cable

Hi,
I'd like only use one cable to my security cameras. They require either 9 or 12 volts and send an RF signal back. At the moment I use precut lengths of cable from Henrys or other sites that have the power connector and a BNC connector at each end. But they are fixed lengths and not that easy to feed through conduit etc.
I'd like to feed the 12v down the RG58 as well as the RF. I think that should be possible with care as this is how mast-head TV amplifiers are powered.
I think I should put capacitors at each end to isolate the RF from the low voltage but I'm not sure what values etc.
Any ideas?
Thanks,
Simon
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Simon Pawson

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If they're really RF, it is easy as you say. Most security cameras are composite video though, and that's much harder as it has a significant DC and low frequency AC components which will get lost or distorted if you add a DC decoupling capacitor.
For RF, you'll need a capacitor and inductor at each end. Do you know what the RF frequency is (roughly only, e.g. VHF, UHF)?
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Andrew Gabriel

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Sorry about that - you are right it is Composite Video not RF (I was looking at wireless as well - that's where I got the Rf from).
I like both the postings about both the forms of two way cables - the twin mic and the RG59 plus power. I may use the latter.
As an aside I'd heard somewhere else that some Cat 5 cable may be relatively porous and not suited for use outside.
thanks for your ideas all,
Simon

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Simon Pawson

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It isn't porous but the sheathing will go brittle in sunlight. You can get special outdoor rated stuff.
Mic cable will only work for a short run, prob less than 10m, without the picture becoming unusable. If you use 75 ohm coax you can run it for a long way, 100's of metres.
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Tim Mitchell

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Do they really send RF? Anyway, unless they are very high quality, or colour, cat5 will work fine for the cable, and has plenty of spare wires for the power. Alternatively, there are many coax and power cables available, money. You may find the easiest available is twin coax.
http://rswww.com / http://www.cpc.co.uk /
I've used in the past 5 wire strips of 0.05" IDC wire. Inner wire video, middle wires ground, outer wires positive. Worked for me, for video anyway, over about 10m.
To do it 'properly', you need a little cir
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I've used balanced mic cable for this (two conductors within one screen) and modified the camera by removing the original connectors and connecting new cable straight in. At the other end (about 20m) it is terminated in a connector which then splits to power and video. Has been installed about a year and working fine. (Colour camera with compesite video output. Video ground shared with PSU ground - pretty standard stuff.)
Alan.
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am.ntlworld.com> writes

If its proper RF via a modulator then its likely to be on 500 odd MHz and this doesn't travel that well over CAT 5, and neither does unbalanced baseband video either, least not for any distance...
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Tony Sayer


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I've used 25m of old appletalk cable, basically twisted pair too, without too much signal degradation. Power in one connector, video in the other. I was going to add capacitors and put audio down the power line too, but never bothered.
Alex
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