POOLEYR 0 Posted March 9, 2015 Hi all I have looked at a number of videos connection CAT5 to camera baluns and their DVR counterparts. They all show a single UTP being used to connect the camera to the balun and same at the other end. One wire in a twisted pair to teh +ve terminal the other to the -ve terminal. I have just inherited a CCTV system that I am about to rewire because the existing wiring is tatty at best and causing repeated problems. When I look at the existing wiring the original installer has used two of the four UTP cables to connect each camera balun. So you have one whole UTP connecting the +ve terminal and another whole UTP connecting the -ve terminal. My immedate thoughts are that if you can get away with one UTP strand per balun terminal why use two? After all, its twice the resistance and the least resistence to the signal the better. Does anybody have any thoughts on this? Why would you use two UTP per camera balun instead of one? I can't think of a reason. How about you guys? Thanks Share this post Link to post Share on other sites
Kiwi 0 Posted March 9, 2015 That is a weird question. The wire pair between the baluns must be a twisted pair, preferably the color with the tightest twist. Not good idea to use more than one pair in any way for video, however using one or more pairs for power is common. Share this post Link to post Share on other sites
survtech 0 Posted March 9, 2015 Why would anyone parallel multiple pairs for analog video? One pair is 100 ohms, which is what baluns are designed for. Two pairs would likely create an impedance mismatch, which could potentially cause ghosts and double images in the picture. There are uses for the extra pairs in 4-pair cable: 2-3 pairs can be used for power or multiple cameras can be transported over a single 4-pair cable (one pair per camera), etc. This reminds me of the people who replace 1 amp fuses with 10 amp fuses, figuring that if 1 is good, 10 must be better????? Share this post Link to post Share on other sites
secplus 0 Posted March 18, 2015 ........ This reminds me of the people who replace 1 amp fuses with 10 amp fuses, figuring that if 1 is good, 10 must be better????? " title="Applause" /> " title="Applause" /> Share this post Link to post Share on other sites
Securame 0 Posted March 18, 2015 This reminds me of the people who replace 1 amp fuses with 10 amp fuses, figuring that if 1 is good, 10 must be better????? 10 times better, of course! So using two pairs on the UTP cable must be twice as good! (/joking) Share this post Link to post Share on other sites
Numb-nuts 1 Posted March 18, 2015 ........ This reminds me of the people who replace 1 amp fuses with 10 amp fuses, figuring that if 1 is good, 10 must be better????? Thats the best one yet Share this post Link to post Share on other sites
jazzar 0 Posted March 21, 2015 1 pair should be used. the reason is that one pair can have different number of twists than a second pair. the signal is measured as the difference (voltage) across the two wires- this is good because any noise present in the cable run should appear on both wires and effectively cancels itself out resulting in only the original signal being processed. different pairs with different twist ratio could allow different noise to be present and NOT completely cancel itself out. looks like installer is getting confused using two pairs. using two pairs means more cross sectional area for signal to travel down or using power allows more current to flow, increasing the cross sectional area means less resistance- so doubling up would effectively half the resistance of the circuit. Share this post Link to post Share on other sites
Numb-nuts 1 Posted March 21, 2015 1 pair should be used. the reason is that one pair can have different number of twists than a second pair.the signal is measured as the difference (voltage) across the two wires- this is good because any noise present in the cable run should appear on both wires and effectively cancels itself out resulting in only the original signal being processed. different pairs with different twist ratio could allow different noise to be present and NOT completely cancel itself out. looks like installer is getting confused using two pairs. using two pairs means more cross sectional area for signal to travel down or using power allows more current to flow, increasing the cross sectional area means less resistance- so doubling up would effectively half the resistance of the circuit. What you are referring to is the Balun changes the signal to a balanced signal hense the name Balun balunced / unblanced I always found using a single pair for the video to be more effective than two pairs and frankly I use the remaining pairs for DC or AC power. The peaks of the signal that is where the noise is, will be cancelled out since a positive plus a negative = nil. judging by what I have seen in the field when servicing and repairing systems, some installers do use two pairs for the signal for one of two reasons, either they think that there is better transmission of the signal or they do it because if one pair should suffer a fracture or break then the signal is not lost as usually one conductor would survive. I follow this thinking but frankly it's wrong and for the reasons you've stated, Share this post Link to post Share on other sites
