Identifying TV Aerial Feed Problems

[Seb101]

The previous owners of my house decided to take the TV distribution amplifier with them when they left, understandable I guess if they'd recently paid for it, but annoying as they didn't label any of the cables. Result: I had 7 identical coax cables running to a location in the loft and no idea which is which.

So I applied a bit of brain power to it and realised if I went round the house shorting out the 6 TV sockets one by one and DC circuit testing them from the loft, I'd be able to tell which was which and whichever one was left over must be the aerial feed. So I did this and identified all the sockets in the house, wired them into the new amplifier and finally connected what must be the aerial line to the input of the amp.

Ran downstairs to check it all worked... NOTHING. Not a single channel. Bugger.

So I went back into the loft and connected what I thought was the aerial directly to a small LCD TV and did a channel scan, nothing again. So I started Googling and discovered that apparently a UHF aerial can look like a dead-short to a DC circuit tester. Suddenly I realised my whole identifying of cables might have had a fatal flaw. So painstakingly one by one I tried every cable directly into the TV and did channel scan. To my ultimate frustration, none of the cables produced a single channel.

Any tips on what to test or look for next? All I have to hand is a DC multimeter (which I understand is woefully inadequate for this job) but I'm trying to save a bit of cash here. I'm fairly certain the cable I've identified as the aerial feed is indeed the aerial feed as it comes from the right place on the house. When tested with a DC tester there is no circuit (infinite resistance) on this line. Is there a way to test for the presence of an aerial on a wire with a DC/AC multimeter?

Thanks!

 

[Sam Gangee]

Firstly, the previous owners have committed an act of theft if "fixtures & fittings" were included in the sale. The amplifier is classed as "fixtures & fittings" because obviously it's part of the TV aerial system. You should ask your solicitor to make a claim for the total cost including installation.

It's possible that the previous occupants never had Freeview and used a distribution amplifier just for satellite TV. If that's the case you'll need to install an aerial. Tell us your postcode so I can recommend the correct type.

Alternatively, there might be a perfectly good aerial with a masthead amplifier. If so, this will need to be powered via the coaxial cable.

As there are several possibilities, I'd suggest simply installing a new aerial unless you can determine exactly what aerial exists and what it's connected to. You won't do this with a multimeter.

 

[Seb101]

Firstly, the previous owners have committed an act of theft if "fixtures & fittings" were included in the sale. The amplifier is classed as "fixtures & fittings" because obviously it's part of the TV aerial system. You should ask your solicitor to make a claim for the total cost including installation.

It's possible that the previous occupants never had Freeview and used a distribution amplifier just for satellite TV. If that's the case you'll need to install an aerial. Tell us your postcode so I can recommend the correct type.

Alternatively, there might be a perfectly good aerial with a masthead amplifier. If so, this will need to be powered via the coaxial cable.

As there are several possibilities, I'd suggest simply installing a new aerial unless you can determine exactly what aerial exists and what it's connected to. You won't do this with a multimeter.

Unfortunately the house was a repossession so I'm not sure I'd have any claim - it was sold 'as-is'.

The amp I bought has a 12v supply for a masthead amp so I think I can rule that out. The one test I haven't done is to try every cable into the amp input (12V) and see if it gives a signal output to the TV through the amplifier... I'll do that tonight.

There is definitely an aerial, I can see it bolted to the side of the house!

 

[ericmark]

Let me run though this and see if I have it correct.
7 cables and without short circuiting they all show open circuit, tried using each in turn with local TV and nothing.
So unlikely a direct connection to aerial, that would likely show a short circuit to DC, so either a de-coupling capacitor or an other electronic component. Seems likely a mast head amplifier even if not mounted on the mast, as said you could try powering, but they may have also taken that. Or simply a damaged cable.

 

[jackthom]

Do all of the cables in the loft come from the same direction and can you see where they head off downstairs?
I'd have thought it would be possible to find the route of the aerial cable which would not normally be bundled in with all the others.

 

[Sam Gangee]

Unfortunately, Seb 101 hasn't been back since 22nd November (over 2 weeks) so I think he's either solved it or lost interest by now.