arfur mo Posted December 1, 2007 Posted December 1, 2007 Tv is 50 ohm impedence where as CCTv is 75 ohm's impedence On CCTv systems the camera shoves out more signal than actually needed to overcome distance and volt drop, the 75 ohm ressistance shunts the signal down for the monitor to be able to cope with it. as the distance could be a few feet to a few hundred feet this is how the signal is 'compensated', bit like the water main being pumped at high pressure, your house feed siphons off only some of the pressure available due to the diameter of the pipe. the fact Tv is 50 ohm and CCTv is 75 ohm is more to do with 'band pass' effect on the frequencies used in each technology. these days you need to run the better quality satellite cable for Tv works so forget old style Tv cable, or problems with freeview may be exasperated, but using Tv cable should not damage any sky boxes for any reason that i know of. Regs Alan If you think education is difficult, try being stupid!!!!
luggsey Posted December 1, 2007 Posted December 1, 2007 Tv is 50 ohm impedence where as CCTv is 75 ohm's impedenceOn CCTv systems the camera shoves out more signal than actually needed to overcome distance and volt drop, the 75 ohm ressistance shunts the signal down for the monitor to be able to cope with it. as the distance could be a few feet to a few hundred feet this is how the signal is 'compensated', bit like the water main being pumped at high pressure, your house feed siphons off only some of the pressure available due to the diameter of the pipe. the fact Tv is 50 ohm and CCTv is 75 ohm is more to do with 'band pass' effect on the frequencies used in each technology. these days you need to run the better quality satellite cable for Tv works so forget old style Tv cable, or problems with freeview may be exasperated, but using Tv cable should not damage any sky boxes for any reason that i know of. Regs Alan TV and video are all 75 Ohm impedence, it's set at a standard impedence to allow the signal transmitted through it to be "matched" to a comman impedence level. 50 Ohm impedence is used for RF signals as the defacto standard output of a radio is looking for a 50 Ohm impedence to match the signal. To sum up, for recieve only there is not a lot of difference in 50 or 75 ohm but when using the coax for transmiting RF energy or feeding a satelite LNB (Dish) with voltage then the impedence becomes more of an issue. Unless you are transmitting, ie pagers, dualcom nurse call etc then you will normally use 75 ohm cable. ----------------------------------------------------------------------------------------------------------------------------------- Life is like a box of chocolates, some bugger always gets the nice ones! My Amateur Radio Forum
Paul P Posted December 1, 2007 Author Posted December 1, 2007 Thanks it was a signal quality question, not a lets pinch some cable of the boss, I just noticed RG59 is made to a better standard than TV coax so thought it may be better for TV signal. Trade Member
Guest anguscanplay Posted December 1, 2007 Posted December 1, 2007 Thanks it was a signal quality question, not a lets pinch some cable of the boss, LOL - I am the boss
Mavrick_001 Posted December 5, 2007 Posted December 5, 2007 Had to use rg 59 as a link a few weeks ago for modulator into tv amp, wasn't happy about it but 150miles from home on a Friday night and with little choice it had to be done, works a treat lol, no sky involved there just tv signal but it did the job. This coming from a guy who hates to see tv coax used in cctv and goes nuts at the very sight of it. Best bet is to use the right cable for the job, even though my slimjim is wired in 75ohm coax instead of 50 ohm as it's a better match..... figure it out lol, it will work chaps but as a general rule stick to what's best I've found CCTV Intruder Access Control Tony Hughes, Proprietor, TRADE MEMBER
Baracus Posted May 20, 2008 Posted May 20, 2008 OK ill do a bit of recycling here to save me opening a new thread.... So to confirm, RG59 is unsuitable for a digital (set top box) signal What is RG6 and is standard TV coax CT100? Currently I have recently fitted a new standard TV Aeriel and a new RTE (Irish TV) Aeriel. I have a box on the roof to combine the signals and have run RG59 from this to a Distribution Amp in the Roof Space. From this is a standard TV Coax (about 10years old) to the living room set top box. My RTE signals through Digital are fantastic whereas my BBC1 etc etc aren't good at all Can anyone advise me on what to go to first? I appreciate this isn't an Ariel forum but hopefully someone can help
james.wilson Posted May 20, 2008 Posted May 20, 2008 Id of said that RG59/U coax was ideal for tv but i wait to be corrected. securitywarehouse Security Supplies from Security Warehouse Trade Members please contact us for your TSI vetted trade discount.
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