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Topic Title: Aerials help.
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Created On: 29 November 2011 02:03 PM
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 29 November 2011 02:03 PM
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I need some help in regards to the installation of an aerial to a seperate room.

How would I go about this? Do i need to go to roof top and attach to actual aerial or can I just add on to an existing aerial in a seperate room?

If so what would I need to do this? I know I need coax cable....but what accessory is used to split the aerial.... Also once split will the signal be ok in each room?
 29 November 2011 02:07 PM
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You need a amplifier/splitter. Divert the lead from the aerial into the amp, then take a coax from the amp to each TV. make sure you buy an amp with enough outlets. The amp will need a 240V supply.
Often the amp can be fitted in an attic.
 29 November 2011 06:21 PM
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Many modern mast-head amps are phantom powered meaning, there is a high to low voltage transformer near your TV and the voltage to power the amplifier is injected on the coax. that provides the aerial signal.

M.I.E.T - Forfeited this due to The I.E.T's ridiculous membership rules!
 29 November 2011 09:01 PM
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Each time you split the signal, you will lose about 1/2 the level. Depending on the original level, you may be able to just cut the downlead, use a splitter and feed each TV. The problem now is the signal produced by the new fangled digital transmitters is a fraction of the analogue and then divided into 6 multiplexes again.

As an example, we get a signal from a transmitter I can see from my garden. The level is poor. It feeds into a PVR which has an amplifier built in (and can feed 5v into a mast head amplifier if required). This loops into a digibox - which just passes through and then into a DVR recorder - again just passes through. there is then a lead going into the loft and into a 4way amplifier to feed other points. Even then, two of the RF channels start at 10% of the other 4 (there are normally 6 RF channels per mast), so we struggle with a few 'channels' . Apparently after a couple more RF channel moves, we should settle with the higher power on all channels.
Interestingly, the 'freeview service prediction' suggests we would be better with a mast situated some 60Km away.

The same mast also carries the DAB transmissions and that is even worse. The 'digital high quality signal' is nothing of the sort and indeed one of the radio stations has just reduced it's bit rate to 80b/s and it's like listening to AM without the whistles.

 16 December 2011 12:31 PM
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Don't buy the cheapest splitter/amplifier either. Get a recognised brand, the stuff from the far east and Mapl*ns is poor at best. Have a word with a good rigger, he'll sort you out.
 09 January 2012 01:34 PM
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You could make a type of balun (balun to unbalanced) but if you wind coil on a toriodal (excuse spelling) ring which is centre tapped making it pass frequency just below passband XL = 2*PI*F*L from centre tap to either end then connect the antenna to the centre tap then connect each remaining end to 75ohm co-ax or an rf connector then screen of the co-ax from antenna to the screen of all remaining connections then this would split the signal from the antenna to both feeds keeping them both in balance at the same time. you would also need to have capacitors in series on outputs as the inductor would put the current 90 deg out of phase to voltage but the capacitors would then get the signal back in phase with voltage (CIVIL)

but be careful just using signal amplifiers yes they split signal for you but they are broad band amplifiers so any transmitters nearby would mess up your signal. try a high dB gain antenna before using amplifiers and investigate the position you are relative to the transmission mast as some masts put out in the reigon of 8KW if you live about 10 mile from the mast then there would be no need to split using amp otherwise your over amplifiy the input stages of the devices. bare in mind tv signals normally at your tv are in the reigon of uW..........
hope that is of some help.....

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