EMC filtering advice please!

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John555
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EMC filtering advice please!

Post by John555 »

My 'shack' is the spare bedroom that I also work from. In here I have 2x monitors, laptop and a 4ch CCTV recorder running. This all adds up to 6x switch mode psu s all runing off the same mains ring and predictably this is giving me a bit of noise on HF, to be fair it's not making the band unusable but I tend to turn it off when the radios are on which is less than ideal as this means no CCTV.

My question is where could I start with trying to improve the noise levels? I have moved the kit as far appart as I can but it is only a small room and I'm constrained by the cable runs for the

Would some chokes on the LV side of the psu s help at all or should I be looking at some mains side filtering? If so can anyone offer any suggestions on products? Thanks in advance
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ch25
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Re: EMC filtering advice please!

Post by ch25 »

Get rid of noisy power supplies, but I think main problem is CCTV POE.
Is it 48V or just 12V?
Almost impossible to get rid of it. Just power it off when on the air.
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John555
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Re: EMC filtering advice please!

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Thanks Chris, it's an old swan recorder very cheap and nasty to be honest. It doesn't use POE just badly screened coax for the video data. Think the cameras are 12v. Poking about with an HF rx with a short bit of wire as an antenna it looks like the CCTV recorder box radiates quite badly so I'll start with re routing the cables and getting it as far from the radio kit and feeder as I can. Thanks
26mb04
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Re: EMC filtering advice please!

Post by 26mb04 »

If you consider yourself competent with electronics you could have a look inside the devices and see if the power supplies could be swapped with better ones. In many cases, any bad or barely-functioning components (dodgy/fake caps, adding inductors to where they should be etc) could be replaced.
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John555
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Re: EMC filtering advice please!

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26mb04 wrote: 02 Dec 2020, 22:51 If you consider yourself competent with electronics you could have a look inside the devices and see if the power supplies could be swapped with better ones. In many cases, any bad or barely-functioning components (dodgy/fake caps, adding inductors to where they should be etc) could be replaced.
Yes that is something I looked at but the psus supplied are all sealed with no obvious way of getting into them without cutting the cases up which I'm not keen on as I need my CCTV up and running 24/7 really.

Im making some cables up to try and power the CCTV recorder and cameras of a single linear psu rather than the s/m ones supplied, I'll report back on progress here. Thanks for youu help :D
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DX-Digger
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Re: EMC filtering advice please!

Post by DX-Digger »

If they are the walwart type powersupplies running each camera at 12V I suggest getting rid of those and aquire a 12V linear psu to run all the cameras etc.
Ok expensive option but a good psu would pay for it self in the long run.
And you get to play radio. Unless ofcourse your radio RF gets into the cctv system then ferrites on leads will be required.
I hope you manage to solve your problem as EMC can be a pain at times to cure, and thats for equipment you own, then there is the neighbourhood Noise level, which sadly raises substatially over Xmas period.
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John555
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Re: EMC filtering advice please!

Post by John555 »

Thanks for the comment dx digger its appreciated.

I'm lucky as where I am is pretty rural so get s0 of noise anyway even with the CCTV on so it's not a big issue for me really, just pulls noise in alongside weaker stations. Recenttly moved the antenna a higher and that has improved things.

Came across this which has been useful but I think my issues are more related to emission from the long cable runs and CCTV recorder box as running the radio off a battery and CCTV from a linear mains supply does not make a massive amount of difference to the noise floor, that said every little helps as they say and u can just power it all down when needed.

Next up will be some better quality coax and possibly some chokes at each end, it's slow going between a million other things to do it I'll report back on progress when some is made!
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