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
A mains filter connects electronic components L. to N., L. to E. and E. to N. internally I believe and causes some earth leakage in the process. This may trip off a sensitive R.C.D. especially if there is other leakage from other equipment and/or the radio equipment induces trip currents into the R.C.D. as well.
You radio amateurs do take your life in your own hands and risk electrocution sometimes. This man has an expensive rig but can't afford a new 13 Amp plug. Just look at the cracked 13 Amp rubber covered plug in the video clip, cracked by the 13 Amp fuse position.
I could snipe a bit and say typical sparks to focus on one detail and miss the bigger picture. Yes the plug on in the video is old - but fact he has made a test socket 2 tails with plugs on it so he can switch from with mains filtering to without is a far greater potential hazard, if you worry about such things. - realise that the pins of the one that is not plugged in are still live !!
Wiring a switch across the filter would have been a safer demonstration.
However, putting that to one side the video is also a very good demo of why filters that do not choke the earth as well as L and N are sometimes quite ineffective against certain types of mains borne interference, and just how good a well placed chunk of ferrite can be. I'd like to hope that after the demo he has taken that test lead apart or at least kept it out of circulation.
I could snipe a bit and say typical sparks to focus on one detail and miss the bigger picture. Yes the plug on in the video is old - but fact he has made a test socket 2 tails with plugs on it so he can switch from with mains filtering to without is a far greater potential hazard, if you worry about such things. - realise that the pins of the one that is not plugged in are still live !!
Wiring a switch across the filter would have been a safer demonstration
No bigger picture missed Mike. I expect that his temporary set up will be put away after the video, but his dodgy mains plug will still be in use.
Wim aware of how mains filters work and what I should of added is that the frequency counter has its own built in filter Part of the reason I got a 10 mA RCD was because I do a few experiments and repairs and I wanted to prevent the house trip going and bearing in mind my poor health reducing shock risk is a definite advantag. Incidentally I got taken in to hospital again last week with a suspected heart atack
If you are rolling your own mains filters as it were, then as in the UK we do generally know which is live and which is neutral, we do not have to have the delta of capacitors beloved of the international equipment. The N_E capacitor and the L_N capacitor can be made quite a bit bigger than the L_E one that causes all the RCD issues, and from an RF point of view L,N and E are well connected to each other. (And as per that video, all 3 cores need to be wound onto a choke as if they were one - there is little point in raising the impedance of L and N, if there is in effect an RF bypass via a low impedance CPC.)
Actually generally in my experience, unless there is a large out-of balance current that would cause magnetic saturation, you can gain more RF isolation from a ferrite ring core than a rod.
A mains filter connects electronic components L. to N., L. to E. and E. to N. internally I believe and causes some earth leakage in the process. This may trip off a sensitive R.C.D. especially if there is other leakage from other equipment and/or the radio equipment induces trip currents into the R.C.D. as well.
Z>
I learnt something today, had never heard of a "mains filter". Is a mains filter potentially dangerous on a PME supply due to Open PEN risks?
When is using a mains filter required? As a radio ametuer keen to understand use cases in a radio shack context too pls.
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.
