As some of you mite remember some time last year I bought a 10mA RCD socket to protect my test/workbench sockets when it arrived I fitted a beefy length of flex to it with a plug on and set it up in position great so far. One of the items plugged in is a frequency counter which I always have on when I'm using my ham radio transmitter it all worked well when I was on 14 Megs and on 7 Megs however when I was on 3.7 Megs the RCD would trip. Disaster! After a bit of head scratching and un lady like language I fitted a mains filter between the RCD socket and the bench socket boards this fixed the problem but weirdly now if I don't have the counter on (I forgot it by chance one day) it now trips whatever band I'm on but all is ok with the counter on. The reason I'm sharing this is because if any of you get trouble with electronic trips then a mains filter mite help not easy to add in a DB I know but thought ide share anyway
If all equipment that had the potential to generate interference was adequately suppressed, and all equipment that had the potential to be vulnerable to interference could be adequately filtered internally, then the mains would be a perfect 50Hz sinewave, neutral and earth would always be at the same voltage, and external mains filters would not exist.
However, a quick glance at for example a typical catalog, reveals over 1000 varitions on the theme, ranging from a capacitor in a box to complex arrangements of torroidal chokes, capacitors and dissipative elements, in a variety power ratings and shapes.
A radio is particularly vulnerable, as a good communication receiver can detect signals at the 100nano-volt level, and even a poor one at a few microvolts.
Mains wiring, depending on its route, and what other loads it supplies, can be an ingress mechanism.
Some other loads can generate strong in-band signals- favourites are accidental spark transmitters, such as brushed motors, and welding rigs, closely followed by almost anything with a switch mode supply, which is most IT equipment these days and some LED lights.
Additionally mains wiring can act as an accidental antenna, and either radiate or pick up signals and in the latter case, bring them into a mains powered receiver by a path that avoids the official route with all the tuned circuits and selectivity.
A mains filter is sometimes useful if interference is coming in that way, though it is often hard to be sure if interference is getting ini via many paths.
If all equipment that had the potential to generate interference was adequately suppressed, and all equipment that had the potential to be vulnerable to interference could be adequately filtered internally, then the mains would be a perfect 50Hz sinewave, neutral and earth would always be at the same voltage, and external mains filters would not exist.
However, a quick glance at for example a typical catalog, reveals over 1000 varitions on the theme, ranging from a capacitor in a box to complex arrangements of torroidal chokes, capacitors and dissipative elements, in a variety power ratings and shapes.
A radio is particularly vulnerable, as a good communication receiver can detect signals at the 100nano-volt level, and even a poor one at a few microvolts.
Mains wiring, depending on its route, and what other loads it supplies, can be an ingress mechanism.
Some other loads can generate strong in-band signals- favourites are accidental spark transmitters, such as brushed motors, and welding rigs, closely followed by almost anything with a switch mode supply, which is most IT equipment these days and some LED lights.
Additionally mains wiring can act as an accidental antenna, and either radiate or pick up signals and in the latter case, bring them into a mains powered receiver by a path that avoids the official route with all the tuned circuits and selectivity.
A mains filter is sometimes useful if interference is coming in that way, though it is often hard to be sure if interference is getting ini via many paths.
