How do I shield a cable?

[farflungstar]

I have a problem with RF - the culprit is the lead (supposedly shielded) from the Vida power supply to the Vida but it acts like an aerial and although I can minimise the problem by moving it around I want to get rid of it completely... Any ideas?

[Barry]

The power supply lead may have a shield, but is it earthed at either the power supply or at the phonostage?

[farflungstar]

I'm guessing it's earthed but it's not easy to take apart to check. Considering the cost if the Vida you would think so

[Barry]

Any chance of a photo or two of the power supply connectors?

[farflungstar]

Will snap a shot in the morning. And native try tin foil!

[Barry]

I was going to suggest tin foil. You can then experiment with where you earth it.

[Rick_F]

If it is screened, the screen should only be connected to ground at the mains plug end.

[CornishPasty]

I see you're in Spain and I'm wondering if your mains has a decent earth. A friend had a villa built out there and the mains came in on a telegraph pole. The earth was a rod sunk in the ground at the base of the pole. We gave up trying to get a good low impedance reading. I think that's why many properties out there have rcd protection.

[farflungstar]

Hi had an electrician take a look and he says I have earth. The problem is I have a ratio station at the end of my Street. It's not the power supply that's the problem it's the umbilical - I guess I could try tob foil and ground at the chassis is the power supply...

[Barry]

Ah! - now that is going to more difficult to solve.

First of all, separate the mains cables from the signal cables, and minimise the length of them all, if possible.

Next find out which cables are picking up the RFI, and minimise the effect by moving the cables (as you have done with the Vida umbilical).

If none of the above eliminates, rather than reduces the problem, then you will have to experiment with fitting ferrite chokes on the mains cables first, then the interconnects. They are not expensive. Fit them close to where the cable enters the equipment.

https://www.amazon.co.uk/Willful-10-Pack-Diameter-Ferrite-diameter/dp/B01E5ALVBW/ref=sr_1_fkmr0_2?ie=UTF8&qid=1489172154&sr=8-2-fkmr0&keywords=ferrite+clamps

[JimC]

Maybe this could help..................................

https://www.techflex.com/prod_cnn.asp

Jim

[farflungstar]

That looks interesting - have mailed them...

[CornishPasty]

Hi had an electrician take a look and he says I have earth. The problem is I have a ratio station at the end of my Street. It's not the power supply that's the problem it's the umbilical - I guess I could try tob foil and ground at the chassis is the power supply...


Did he take an impedance reading?

[farflungstar]

Hmmm no

[Barry]

How are you getting on with this Adrian? Has the shielding helped? Have you tried ferrite sleeves?

[alphaGT]

You could always burn down the radio station, I mean use a more highly shielded cable. I have picked up radio waves right in the speaker coils, I could hear the man's voice while they were disconnected! Having a station that close can be a problem. Hard to say where it enters the system? Place the whole system in a Faraday cage?


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[farflungstar]

I managed to site the PSU and umbilical so that I got almost zero audible interference. But I just received a new custom made rack and will be changing things around so the problem might be back....