Roof aerial with power cable?

Discussion in 'Freeview & YouView' started by Marc, Jan 24, 2008.

  1. Marc

    Marc
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    I've just moved into a new house, and there's no freeview/analogue reception at all from the coax socket, but leading from the aerial on the roof, into one of the rooms is an AC three wire power cable which has had the plug cut off. Do some outside aerials need power, or is this unusual, as I was thinking of getting a new end and wiring it up..?

    Thanks

    Marc
     
  2. GaryB

    GaryB
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    If you're sure that the mains connection is related to the aerial, the most likely explanation is that it powers some sort of amplifier. This could be a "normal" amplifier, in which case it's probably lurking in the loft somewhere, or a masthead amplifier, in which case it's possibly a lump on or near the aerial mast. Best to trace the wire before you connect anything to it.
     
  3. Marc

    Marc
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    yes, there is a lump on the aerial mast - that explains it.. would the amplifier need to be powered for the aerial to work or should it still pick up a decent signal without it?
     
  4. GaryB

    GaryB
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    If the signal is routed through the amplifier (which it sounds like it is), the output will probably be virtually non-existent without power, basically just whatever leaks across the PCB in the amplifier.
     
  5. Marc

    Marc
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    thanks Gary, i think it's definitely worth trying to attach a plug to it then, before we get an engineer in to look at it!
     
  6. ched

    ched
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    Please be Very careful. Most modern mast head amps have a 12v feed via an aerial cable. This because having a masthead amp going wrong will only result in any device connected to it getting 12v not 240Vac. If you are going to try it please put an earth leakage trip plug on the feed that goes to the aerial. Also make sure you check for any voltage on the aerial cable before you touch it.

    I know all this sounds a bit over kill but if it is faulty there might be 240Vac on the aerial cable. If you are lucky you will get one hell of a kick (probably enough to throw you backwards) from 240Vac. Worst case IT CAN KILL you!!!!!!!

    Please be very careful.
     
  7. Marc

    Marc
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    don't worry, i wasn't planning on going out on the roof,with my balance that'd be an accident waiting to happen. I put a plug on the cut wire today and switched it on, but nothing happened and the coax in the lounge still has no reception.

    we've got an engineer coming to sort it out on monday now apparently.
     
  8. ched

    ched
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    I didnt just mean 240Vac on the aerial itself but at the plug end of the aerial cable!!!!

    Any way hopefully 'engineer' will sort it without too much cash involved :)

    If you are thinking that in the future you might want TV's in other rooms Monday is the time to get it done, as if 'engineer' as the kit then it would be cheaper to install multiple aerial feeds at the same time.

    I recently had a 10ft pole, bracket, variable gain 4 way masthead amp, and feeds put in 4 rooms. Cable lengths varied from 5 meters to about 35-40meters thats why the variable gain masthead amp type was used. The total cost was about £250 I think. So that may give you an idea of costs, although it does depend on the area you live in. If you have a choice use a CAI registered installer as they have to use approved cable and aerials and they are backed by a proper guarantee.
     
  9. Marc

    Marc
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    i hope it doesn't cost that much, i don't even want the aerial to work, i hardly ever get to watch my dvd's with all the crap my girlfriend insists on watching on freeview!!
     
  10. ched

    ched
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    :D I must admit I am very lucky, at about 10 each night I watch TV, well recorded stuff and DVD's in the cinema room :D Before that 'we' watch tv in the lounge, well my partner watches tv and I surf ;)
     
  11. maldonian

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    Feeding mains to a rooftop aerial would be extremely dangerous, as ched has already pointed out. Masthead amplifiers are invariably powered by a low voltage, low current supply fed up the coax (typically 12V DC).

    Some lightweight aerial rotators are connected using 3 core cable. The cable connects the rotator to a control unit in the living room. The cable only carrys low voltage (typically 18V AC), but the cores need to be thick enough to carry the current to drive the motor, and since the cable is normally bought separately, mains flex may be used.

    So perhaps the previous owner had a rotator, which he removed, but he left the control cable. If you've got a rotator on the mast it should be obvious (a large bulge in the mast, often with the mast above the rotator offset from the mast below it) but it won't be any use without the controller.

    However if the previous owner used an indoor amplifier as a masthead amplifier, don't use it. It should be removed and replaced by a proper masthead amplifier, i.e one designed for outdoor use.
     

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