advertisement


Broadband: Old TV caused village broadband outages for 18 months

I wonder if the offending TV was close to the Openreach cabinet, or on the same electricity phase as the cabinet.
 
That’s quite hilarious. Cyber threat comes in form of stockpiling 1970’s Sony Triniton CRTs.
 
I used to have a British TV from that era with a live chassis and thyristor half wave power supply. It generated incredible RF and mains interference. One of the reasons that CE testing was introduced.
 
And yet ironically the use of 'power line adaptors' where the broadband RF is carried over the mains wiring, is the source of a lot of RF interference these days, not to mention the proliferation of devices with unshielded crappy switched mode power supply units. As an example, the noise levels in the evening coming from the neighbour's house here causes all sorts of carriers, noises and buzzing across FM when pointing the aerial that way. Forget expensive cables and mains isolators. If these devices were all switched off the FM band would be so much quieter and cleaner, and would probably do more to improve the sound quality on FM than any foo.
 
It would be interesting to know what TV it was, and whether it was broken (I assume it was)? 4/3 CRTs are still very popular in the retro computer gaming community along with old CGA and VGA computer monitors. Vintage 8 bit stuff just looks totally wrong blown-up on big modern LCD screens.

I’ve got an old 21” Sony Trinitron from the late ‘90s, one of the last to have a 4/3 ratio, that thankfully I never got around to throwing out for just this purpose. It had been sitting unused under a pile of dust in my bedroom for about 18 years but I put it back into service as my 50” 4K job hasn’t got a SCART or RGB input (plus 8 bit stuff looks crap that size). I use it with the BBC B via RGB/SCART and the ZX Spectrum via composite and it works a treat. No leaky or bulging caps I could see and a great picture. It certainly doesn’t do anything to my router/broadband!
 
Police are looking for the offender who has absconded.

Eif4gQnU4AIwnun.jpg
 
The noisy TVs were discontinued when the AV (SCART in the UK) connectors came into use. Live chassis was no longer possible.
 
'cos an RF noisy TV is a rare thing now and hardly any spotty Broadband 'engineer' (technician probably) would even thing about such a thing. Such tv equipment was dying our before those kids were born. As it happens they did end up using an RF sniffer to identify what was going on - some chap turning on his old tele for the new at 7am each morning.
 
When I did my VHF radio licence exam, the tutor told us the story of a local man who, one evening answered a knock on the door to be greeted by four police officers, an official from the Irish Department of Communications and a technician with a portable direction-finder. All six marched in, stopping only to hand the houseowner a warrant on the way, and a few minutes later, they marched out again, with his fancy new Plasma TV set in their possession. A fault with the set had caused it to intermittently broadcast on the 121.5 MHz maritime distress beacon frequency, and the officials had been looking for it for months. When they finally found it, there wasn’t much patience left.

This kind of thing was common enough that the 121.5 MHz system stopped operating in 2009, replaced with a less-easily spoofed digital version* However, there was still time at the end for Breitling to launch a watch with a 121.5 MHz distress transmitter in it. Given that the penalties for using such a device in a non-emergency was a fine, and confiscation or destruction of the transmitter, it was just as well the system was retired shortly after: the police have better things to do than raiding London wine-bars and smashing watches, no matter how satisfying it might be for bystanders to witness...

(* Even still, pleasure-boat owners regularly set off the alarms by not storing their EPIRB properly over winter: for reasons that should be obvious, when the device gets wet, it starts transmitting - it does not know the difference between seawater and a pool of rainwater, though)
 
We've* had a good think about this and can only assume it's a nasty switch-mode power supply radiating RFI or feeding it back into the mains. It's hard to think of a fault in a CRT that could radiate that much energy and still work as designed. It's also yet another reason why we shouldn't be sweating the copper lines for broadband.

*My local bunch of radio amateurs, and some broadcast TV engineers that I work with and know. Actually, the TV engineers are hams too, come to think of it. I can only assume there were no radio amateurs in that village - they'd have been straight round to sort it.
 
The power supply for the Sky dish on the top of my block of flats turned out to be the cause of my broadband dropping to 0.2mbs.

I only found out when it failed.

Openreach had no idea.

Stephen
 
We've* had a good think about this and can only assume it's a nasty switch-mode power supply radiating RFI or feeding it back into the mains. It's hard to think of a fault in a CRT that could radiate that much energy and still work as designed. It's also yet another reason why we shouldn't be sweating the copper lines for broadband.
There was a time when TVs used a thyristor with phase angle firing control, just like old light dimmers, to regulate the main 200V dc power supply. This was a half wave circuit and generated horrendous harmonics on the mains. This was when a proper SMPS would have been expensive. You would have to be 60+ to remember these
 
We once built a Jacob's Ladder using a computer monitor Flyback transformer - it generated spectacular levels of RF interference!
 


advertisement


Back
Top