…Directly-radiated signal strength from a point source attenuates with radius by an inverse-square law, though I’d still not want to bring down one of the helicopters often flying over my village, albeit probably at some hundreds of feet altitude. Is that a realistic hazard with a low-powered “DIY” welder? What is the range at which they may be a nuisance to anyone, let alone a danger?
Back when I was in short trousers rule of thumb for a communication system was that a watt could be detected a million miles away. Depends on an efficient antenna, and one of the things that makes EMI tricky is that dodgy gear puts power into the wiring which happens to be just the right length to radiate efficiently. Radio, TV, satellite, mobile phones, Wifi, pacemakers, emergency services, aircraft, Bluetooth and utility control systems are all vulnerable.
Although not wrong to assume the nuisance extends metres rather than kilometres, whether or not poor gear causes a problem is pure luck. The perpetrator has no idea he’s a pest unless he has suitable test gear or someone tracks him down. Here’s an example, in short:
The mystery of why an entire village lost its broadband every morning at 7am was solved when engineers discovered an old television was to blame.
An unnamed householder in Aberhosan, Powys, was unaware the old set would emit a signal which would interfere with the entire village’s broadband.
The owner, who does not want to be identified, was “mortified” to find out their old TV was causing the problem, according to Openreach.
Note the power output of a rogue TV set is tiny compared with a welder!
The noise put into the mains may be a more serious proposition. Are 13A plug-in mains filters readily available?
Yes noise in the mains is also problematic as well, potentially energetic enough to damage nearby equipment; hence Lidl’s stiff disclaimer. They are not responsible if the welder isn’t operated within guidance that’s hard to apply in an ordinary workshop.
Though plug-in mains filters are available they don’t work well. Effective filters are difficult to engineer and easily bypassed unless designed and installed ‘just so’. A shielded box and carefully chosen components are needed. These being rather pricey are often omitted to keep prices down…
Man-made electrical noise is about 18dB above the natural noise floor where I live. Decibels are logarithmic, so that’s times 63 worse than it should be in real money! Happened to be running a battery powered receiver when god provided a power cut and I was able to see the difference! The racket reappeared when the power came back on. Comes from the myriad of electrical devices we buy on the cheap, a proportion of which are dreadful or faulty.
Broadcasters deliberately beef up their transmitters to overcome high levels of local noise, but people who live in areas of poor reception suffer. Mobile phone coverage is done with much less power, and interference is one reason the service is somewhat unreliable. A dodgy welder persistently used in the wrong place is a hissing and an abomination.
Dave