The mystery of the TV aerial

Before I moved into the new house, I’d asked about the TV aerial and the owners confirmed it was in the loft. We knew that there socket was in the room I was planning to use as an office but nothing in the lounge. So my first idea was to add a splitter to extend me from one room to the next. I checked the office socket and the signal was extremely weak. I knew the previous owners had mostly used satellite so thought perhaps they had disconnected it. I tried a couple of other sockets and still a very weak signal which kept dropping out.

I checked online and found a map of TV transmitters. My nearest main transmitter was behind a hill but there was a 2w relay nearby (I later discovered it was 12w). Looking out of my window I could actually see it. So I’d expect to be able to get something, as someone suggested, “with a wet bit of string”.

Given the closeness, perhaps a small set top aerial might work? So we bought a really cheap one from the supermarket and it was quite ineffective, enough to detect the channels but poor quality signal which kept breaking up.

There is an aerial in the loft I’d been told. So I headed up into the loft and spotted a cable at the far end. I made it all the way to the end and followed it from the floor and up onto a beam, from there it turned back the way I came. I followed it along and it turned down again. The run to the back bedroom, I speculated. So the source must be the old garage, which had its own loft.

In the second loft I found the aerial. It was in good condition. There was a spaghetti of cables and splitters but no obvious loose connections.

I took a photo and checked with twitter. They came back with:

  • Check for degraded cables.
  • Loose connections.
  • Is the polarisation correct vertical or horizontal, main transmitters are typically horizontal and relays are vertical.
  • Is it the right kind of aerial, the colour on the end of the aerial means what range of frequencies it works best with. Many channels moved when we swapped from analogue to digital transmissions.

I had spotted that the wire from the aerial went into a box marked amplifier and there was no obvious source of power for that. On further research I discovered it was a U25 mast head amplifier, these get power through the coax by applying 12v. Several of my twitter followers had also spotted this and suggested I check for power. As my multimeter was out of batteries and my searches had found no obvious source, I concluded this was the problem. Again the followers agreed that an unpowered amplifier would had the opposite effect and degrade the signal. I had a socket based plugin amplifier which did help and improved the signal so I concluded application would work.

There was little difference in price between a power supply for the mast head amp and a distribution amp with 4 outputs which came with masthead power. So I bought the latter and wired it in. I put a new long run of cable down to the lounge, approx 15m. And with the aid of a bamboo skewer taped to the end of the cable, poked it through the cavity wall.

One top tip from Old Metal Guru was to include a “water break” such as a socket and patch lead. If water gets into the end (or a break) of the cable then the coax cable acts like a straw and water will trickle down. If You have a socket on the wall the water will stop there. If you plug directly into the TV then water could end up running down the back of the TV.

I fitted an F connector to one end of the run to connect to the amplifier. On the other end I fitted a temporary UHF connector and plugged it into the TV. The signal meter now showed 100% signal and 95% signal quality. The distribution amp had a built in 4G filter so I removed the little one that was originally in the back of the TV. I’ve still to put a proper socket on the wall and tidy the cabling in the loft but the system is operational and we can now get our news in both English and Gaelic.

Leave a Reply

Your email address will not be published. Required fields are marked *

 characters available

Notify me of followup comments via e-mail. You can also subscribe without commenting.