Today a Housing Association rung up. "Can you go to Sunset Villas urgently? There's two things wrong. First, the alarm company say there's a serious fault with the aerial system, and secondly some of the residents have really poor reception since Tuesday."

"What's the alarm company got to do with it?"

"They've fitted a camera in the front porch and the picture won't come through on the residents' tellys, so it must be a fault on your system."

At Sunset Villas I was greeted by the warden. "Ohh, they're all going mad! Their tellys are really awful, especially BBC 2, and Mr Stubber says his Freeview won't work at all!"

"When did it all go wrong?"

"Tuesday last week."

"When was the camera installed?"

"That was Tuesday as well. Funny that, isn't it? Do you think they might have pulled a wire out?"

"Probably."

"Anyway, the alarm man says your aerial system is rubbish!"

"Oh he does, does he?"

"Yes he says it's absolute rubbish!"

I suffer from attacks of the red mist, and I felt one coming on. Right, I thought, we'll blankety-blank see about that!

I had pulled this system back from the grave about five years ago. Paul and me had gone through it from end to end, replacing virtually everything, and we'd made it absolutely perfect. Then about a month ago Mr Stubber's son had rolled up with an old ITV Digi box and played pop because only the BBC channels came through. So I'd had to convert the system for DTT. The system uses Belmont for analogue channels 1 to 4, and Emley Moor for C5. The digi muxes had to come from Belmont, so the conversion had involved a Gp CD aerial for all muxes except 1, which came off the existing Gp A Belmont aerial. All 11 channels had filter/levelers, and the whole thing was just lovely when I'd finished.

Everything had then worked perfectly until the arrival of Mr Stupid Alarm Contractor. He had fitted an AZ modulator to convert his camera output to UHF. He had snipped the Gp A aerial downlead between the masthead amp power supply and the filter/leveler block. I'm guessing that he had added his modulator output via a splitter, then spent ages setting the modulator output to every conceivable channel and wondering why he was getting no results, going down time after time to try to tune in his camera picture on residents' tellys. I'm going by the blow-by-blow account from the residents and the fact that my cable had been cut and the two ends joined by twisting together. He wasn't likely to succeed, since the aerial signal levels at that point (after the masthead amp) were far higher than the modulator output, and he was either going to be on a channel already occupied or on a channel without a pass filter. Next he chopped into the Group CD line. There is no masthead amplifier on this line. Instead, there is a 20dB amplifier before the filter leveller. He fitted his nasty plastic Y splitter before the amp (that's where I found it) and inserted his camera picture there.

Again trying channel after channel, he eventually landed on channel 68. This channel is 'the pillocks last refuge'. Whenever someone needs a clear channel and they don't know how to find one they always resort to 68. The trouble is, 68 is mux A from Belmont. Since he was putting his camera signal in before any amplification his analogue channel had some chance of competing with the mux. In fact his analogue video was +10dBmV and the mux was -15dBmV. The result was that reception on mux A was well and truly banjaxed, and his camera picture was very very very snowy. All the other muxes were 6 or more dB down thanks to his crappy splitter, so all the digital reception was marginal.

I then discovered that the four analogue channels from Belmont were all to pot, with three being very low and one being very high. Of course, Mr Stupid Peabrained Alarm Contractor has twiddled all the variable attenuators on the filter/levelers! All this, and the power supply unit for the modulator was plugged into an adapter on my board, and was hanging with its full weight by the mains lead. The video input to the modulator was via a phono plug and a short bit of cable, obviously cut off a scart to phono lead, taped to the end of a length of brown coax that came from the camera. And this man tells the staff and management that my system is 'rubbish'!

Revenge is a dish best taken cold. I put everything right. I added a filter for his blessed camera and found a clear channel (43) for it. I added local radio to his channel on the grounds that silent channels are dangerous. There's fire risk if the residents leave the TV on that channel overnight or unattended. My huge invoice was accompanied by a detailed report with photographs. As I left I told the manager to get the alarm man back to retune every one of the 60 TV sets and approximately 30 VCRs to the camera channel. I added that he would have to check reception of every TV channel in case the residents had attempted to correct the poor reception by knob twiddling. I also told the manager that if he went back up to the head end it would probably result in another big invoice, so it might be best to stop him. I mentioned in my report to head office that the picture from the camera could only be expected to be poor, since the said camera was a DIY item worth at most £40. And you thought I was a nice guy!