Wright's Aerials
Ten taped ‘T’ junctions and a wailing woman

Suppose you had to connect ten TV sets to an aerial. The tellys are in a ten-storey building, one on each floor directly above each other, so they are about 3 metres apart. You could get a 30 metre length of coax and run it down the building, then cut into it near each telly and splice in a short length of coax to run to that TV set. By ‘splice in’ I mean just that – make a ‘T’ junction by twisting the cables together.

I bet most people reading this will be thinking ‘signal loss . . . mismatch . . . standing waves . . . WHAT?’ Obviously, it wouldn’t work. No one would really do that, would they? Not even the most idiotic aerial rigger in the whole world would do that, would he?

The way they used to install distribution systems in the 60s and 70s was by dropping a cable the full height of the building down a conduit in the wall. This passed through each TV outlet backbox. The wallplates were special ones called padded outlets that included a tap-off unit. This tapped off a tiny fraction of the signal and sent the rest down the line to the next outlet. Matching and loss were reasonable, if not good. It was OK for VHF, but a bit dodgy for UHF.

Today I went to a ten-storey block built in 1970, and found something that astonished me. There had been constant complaints about the TV system for years, with the landlord refusing to do anything much about it, but last week a few residents kicked up about the poor TV reception to the extent of threatening a rent strike. The system had been installed all those years ago and everything except the aerial was original equipment. Instead of calling in a ‘proper man’ (me!) the managers called in the local aerial man. I just can’t imagine what this man’s mental processes were, but he carefully removed the printed circuit boards from the backs of the outlets, and twisted together the incoming and outgoing cables and the flylead. He’d cut one plug off the flylead. He did this ten times, and each time he carefully fitted the outlet over the backbox with the flylead coming through it, and I bet he thought he was doing a smart thing.

The results were interesting. It wasn’t possible to make a meaningful signal level measurement anywhere, because the whole thing was a seething mass of standing waves, but broadly speaking the loss from end to end was 55dB. Normally it would be about 20dB. In general the signal level and quality deteriorated from the top to the bottom of the building. The lower four flats had virtually no reception. On frequencies where the signal returning from the end of a flylead exactly cancelled out the signal on the main cable there was a deep notch. One of these coincided with the analogue audio on ch41, making the sound very weak and ‘buzzy’ at all the lower flats. There were all sorts of weird effects, including patterning that I guess came from TVs on the floors above.

The whole system needs to be replaced, but as a temporary measure I fitted new padded outlets (from a box of oddments left over from the 70s!) and added an amplifier at the top.

In a sense I miscalculated the optimum degree of improvement, because that corner of the building now has noticeably better reception that the other three corners, and you know how people talk. Having averted a rent strike by a maximum of ten people I might have caused one by thirty people! Secretly I’m pleased!

So where did the wailing woman come in? Well, she was nothing to do with the flats. The other cowboy story that’s come my way this week started with a lady who rung up in some distress. She’d seen an advert for a firm in the local free sheet. When the bloke turned up he refused to put the aerial on the roof because ‘he was scared of heights’. I know, I know! It turned out that he was a redundant Sky fitter who’d just set up on his own. He only had a little ladder.

The house was a rather nice 30s semi in quite a posh area, but like a fool she let him fix a 16ft mast to the front wall next to the bedroom window. He took £100 off her and scarpered. Apparently the aerial looked so bad that the neighbours have complained! Her father–in-law came round and said it was a monstrosity and called her a daft cow, then her dad came round and instead of being sympathetic as she’d expected took much the same line as the father-in-law. She rang me hoping to get things sorted out before her husband came home, and I’m afraid I didn’t immediately sense how upset she was. I launched into a lecture about Trading Standards and tradesmen who ask for cash, and she burst into tears! The ridiculous thing is, this isn’t some dumb female. At work this woman is a tough professional.

In the end it was put right very easily. The wall brackets almost fell off the wall of their own accord, not leaving much damage because the holes were in the mortar. Well they would be wouldn’t they? A simple little aerial on the chimney and a cup of tea later and all was well.

Print this page © 2003-2012, Wrights Aerials Add to Favorites