[RFI] How much RF does your power company deliver along with the AC?

Christopher E. Brown cbrown at woods.net
Fri Aug 21 20:50:39 PDT 2009

On Fri, 21 Aug 2009, Jim Brown wrote:

> On Fri, 21 Aug 2009 17:48:14 -0500, kd4e wrote:
>> I fail to see a down side.
> Dollars extracted from one's pocket to pay for something that does
> no good. Time wasted installing something that does no good.
> I'm still looking for the circuit diagram.
> 73,
> Jim K9YC

Jim, I do have noise on both hot, neutral (AC grounded conductor) an by 
extension AC ground (AC grounding conductor).  This can be easily detected 
with a small coupling loop from any of the AC wiring in the house.

My original noise issues were 99% radiated noise.  The main antenna is 30 
feet from the closest AC (4 circuits with legs along the closest outside 

The L does not have any issues with this noise, I am still tracking down 
radiated noises, but the overall noise-floor is fairly low these days.

The dipole or any other attic/over to roof w/ drooping legs/etc antenna I 
may place would be similar to the in-attic dipole.  That is to say about 
10ft from closest and within 20ft of some 30 circuits and hundreds of feet 
of romex.

I assume source of this wide-band noise that is weak enough to be a total 
non-issue for an antenna 30 - 40 feet away, but appears to couple well 
into a 32ft dipole in closer proximity is the summ of the conducted noise 
from nearby houses.

Since I am very limited on my ability to place antennas outside of the 
close coupling range, and I really do want to add a few, I would like to 
reduce this noise, while fully understanding that under more normal 
circumstances this level of RF on the AC lines would be a total non-issue.

I hope to find a simple multi-stage filter similar to say a 20a corecom 
like I feed the rackmount computer gear with.

I could build a simple 2 phase + neutral balanced multi pi or similar with 
the T157-26 powdered iron toroids and X class capaciters I have on hand 
*BUT* this would only be valid at < 20amps.  I have seen some very simple 
designs in commerial use that are just that, with about 100uh per line per 
stage.  Even if I had the materials to extend this to a 200amp design, no 
way would I wire it into the feeder, and no way it would pass NEC reqs.

A 200 amp multiple phase filter tends to be of the solid conductor 
(rod or bar) passing through gapped and glass taped iron inductors and 
toroid shaped caps, simple sturdy servicable design.  I have seen all 
sorts of them in industrial/datacom/telco use over the years.

The ideal would be a nice brick in box design meant to wall-mount and take 
a feeder in one side and pass the output on the other.  I already known 
where I could get a custom filter designed and built to whatever spec, but 
it would be very expensive (custom) even before I had to pay for the EL 
cert myself (NEC reqs).

I was hoping for someing COTS.

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