[RFI] GFI Problem

Ian White, G3SEK G3SEK at ifwtech.co.uk
Fri Feb 7 07:48:22 EST 2003

Michael Tope wrote:
>Does anyone out their have any suggestions for RFI proofing
>Ground Fault Interuptors? Specifically, several of the GFI's
>in my house (and occasionally their associated circuit breakers)
>trip when I am transmitting on 160 meters. The best solution,
>of course, would be to get my 160 meter vertical further from
>the house, but this is not practical since my lot is very small.

I had a similar problem of RF getting into the mains, in my case because 
the extra loading wire needed for the inverted-L on 160m brings the hot 
end of the antenna too close to the house.

>I am wondering if  RF bypass capacitors or ferrite beads
>judiciously placed on the affected circuits would be the way
>to solve this problem?

A better solution is to keep your RF out of the mains wiring completely. 
Quite probably you have RF in the mains because your 160m antenna has 
"conscripted" the mains ground wiring as part of its grounding system. A 
three-wire mains filter (including a ground-line choke) for the whole 
shack should stop that. The other part of the solution is to improve the 
RF grounding at the base of the antenna - which will be good news for 
your signal strength.

That solution worked here... but only after making sure that *all* of 
the shack's mains connections passed through the filter, with no sneak 
paths around it.

The three-wire filter cannot prevent RF current being induced into the 
general mains wiring of the house, but that should be much smaller than 
the directly-conducted component which the filter will stop.

73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
                            Editor, 'The VHF/UHF DX Book'

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