schmo Posted July 1, 2008 Posted July 1, 2008 Hi, just got some guy to come split my rooftop cable from my antenae to put a socket in my room however found that my aerial only had ribbon cabling (its old old old). The guy ran coax down from the roof but couldn't connect the coax to the aerial (i presume). Wondering if getting a converter would be easy enough as the coax cable is already run into my room... any ideas? Cheers!
digitalj Posted July 1, 2008 Posted July 1, 2008 you should replace all the ribbon cabling with RG6 Quadshield Coax Cable as opposed to getting a "converter" i.e. a balun.
mtv Posted July 1, 2008 Posted July 1, 2008 From your description, it sounds like the 'guy' didn't have much knowledge about antennas and cabling. If the antenna is designed for 300 ohm connections, as with ribbon cable, then a balun to suit the coax and antenna terminals would have been the solution... however... if the antenna is old, it is probably not designed to receive all digital channels anyway, so replacing the antenna would probably be best. 300 ohm ribbon cable is not suitable for digital signals, so all cabling should be replaced with good quality coax, such as RG6 Quadshield and all connections, splitters outlet plates etc should use fully-shielded 'F' type connectors.
schmo Posted July 1, 2008 Author Posted July 1, 2008 From your description, it sounds like the 'guy' didn't have much knowledge about antennas and cabling.If the antenna is designed for 300 ohm connections, as with ribbon cable, then a balun to suit the coax and antenna terminals would have been the solution... however... if the antenna is old, it is probably not designed to receive all digital channels anyway, so replacing the antenna would probably be best. 300 ohm ribbon cable is not suitable for digital signals, so all cabling should be replaced with good quality coax, such as RG6 Quadshield and all connections, splitters outlet plates etc should use fully-shielded 'F' type connectors. At the current time im recieving perfect digital tv (through a HD set top box) on my other tv... through the same ribbon cabling. Will this mean that it won't be required to change over? - as i really don't wish to fork out that much money (im a student) so if i can just attach the connector that would be best! Thanks
schmo Posted July 1, 2008 Author Posted July 1, 2008 If it's working ok, then no need to change anything. Great Is my best course of action to hook the coax converter to a lose ribbon cable coming from the aerial?
wahroonga farm Posted July 1, 2008 Posted July 1, 2008 (edited) 300 ohm ribbon cable is not suitable for digital signals ...... It would be more correct to say that: '300 ohm ribbon cable is not suitable for (VHF) digital signals ...... unless it is installed with suitable stand-offs from metal surfaces, always crossing power cable at right angles with as much distance as possible, and is uniformly rotated to prevent it becoming part of the antenna system with the attendant introduction of multi-path signals.' With good installation practice it has marginally lower transmission loss (dB/metre) and adequate impulse noise immunity. 300ohm closely matches the balanced output impedance of a folded dipole ..... the most common active antenna element in a Yagi aerial. Transmission line to TV input matching is easily achieved with a 300ohm 75ohm balun. More correctly (I suspect), it is less suitable for uhf transmission, where poor installation technique magnifies it's susceptibility to induced noise and impedance changes. And the big ones. It also has much poorer life; with dramatic signal loss as it weathers and ages, is cheaper to manufacture but more labour intensive to install and simply looks crappy, even with the best installation technique. So basically we now use a good induced noise shielded, more robust and versatile transmission line, with impedance characteristics that are readily maintained with limited skill and knowledge. Simply chuck it in the roof and it works Ist time every time. It's the price of progress Edit: PS So not surprising that it works just peachy. Edited July 1, 2008 by wahroonga farm
mtv Posted July 1, 2008 Posted July 1, 2008 Is my best course of action to hook the coax converter to a lose ribbon cable coming from the aerial? If the antenna has ribbon cable connected to another TV, then you will require a splitter..... not sure if there are any splitters still available that accept both ribbon and coax. eg: ribbon input and one output ribbon, the other output coax.
charlesc Posted July 1, 2008 Posted July 1, 2008 ...300ohm closely matches the balanced output impedance of a folded dipole ..... the most common active antenna element in a Yagi aerial. Transmission line to TV input matching is easily achieved with a 300ohm 75ohm balun. Well, all the more reason to use a log periodic then that matches the 75 ohm line directly. No need for a balun at all...
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