[RFI] Troubleshooting AFCI Tripping Due To Amateur Transmissions

Roger (K8RI) k8ri at rogerhalstead.com
Fri Jan 4 10:04:47 EST 2013


On 1/3/2013 3:15 PM, Jeff Stevens wrote:

First we are dealing with two issues, one of diplomacy/cooperation and 
one of a technical nature.

Before calling the ham a prick for not cooperating (such do exist) I'm 
interested in why he has chosen not to cooperate.  How was he first 
notified there was a problem?  Did they get along prior to the RFI? 
IE: is there any history between the ham and neighbor, or between the 
ham and neighborhood, or any other neighbors. Normally when some one 
doesn't want to cooperate there is a reason and it's quite often 
from/because of the initial contact or some history within the 
neighborhood or even prior history from some other location.

As to the problem, it sounds to me as if there is a grounding problem as 
a properly grounded GFI shouldn't care about RF.  Are perchance both 
houses on the same transformer?  (Hope not as that could be a major 
problem.) are the grounds properly tied to the panel.  Are they 
contained in the Romex the full length?  Is any thing not on that 
circuit tied into the ground.  Does that ground tie into any other 
grounds such as water pipes?  Many Electricians tend to think ground is 
ground and all are created equal and of course when RF is involved they 
aren't. Does the neutral have a good low resistance connection back to 
the pole transformer?

73 and good luck,

Roger  (K8RI)

> A friend of a family member is experiencing an apparent RFI issue which is
> causing his code required AFCI outlets to trip, apparently due to his
> neighbors amateur transmissions.  This is in the Southern New Hampshire
> area.  Unfortunately, unlike many of us in the amateur community (who would
> relish the opportunity to troubleshoot such an interesting RFI issue) the
> operator seems unwilling to provide even a basic level of assistance.  To
> clarify, this is a situation where a licensee is apparently causing
> interference to a Part 15 AFCI in his neighbors house.  While the licensee
> may not be under any legal obligation to help troubleshoot the RFI issue,
> I'm hoping we can come up with a solution for the neighbor.  The neighbor
> has apparently spent hundreds of dollars in material and labor to have an
> electrician attempt to remedy the problem without success.  Several brands
> of AFCIs have been tried with no improvement.  The licensee has been
> unwilling to provide even basic assistance such as what bands he operates
> on, what power levels he uses, or what times he operates.  I'm looking for
> suggestions on how to reduce the RFI which the neighbor's AFCIs are
> experiencing which will hopefully eliminate the erroneous AFCI trips.
>
> The little information we know about the licensee is that his antenna
> systems are wire only.  There appear to be no HF/VHF beams or highly
> directional antennas on the property.  I have not seen the antenna systems
> myself and these are only third party observations.  In addition to being a
> licensed amateur, the operator is apparently an RF engineer as well.  With
> this in mind, it's likely the licensee is operating on HF of MF, possibly
> QRO.
>
> The only suggestion I've been able to come up with on my own was to build a
> choke by running the romex wire leading to the neighbor's AFCIs through a
> large toroid of the appropriate material.  This would simply be an attempt
> to prevent any induced MF/HF current on the electrical system from reaching
> the AFCI while allowing the 60Hz AC current to pass through unhindered.  Of
> course, we aren't sure what frequency the licensee is operating on so we
> don't know what material to select.  Our assumption that this is MF/HF
> interference may not even be correct -- the licensee may be operating on
> VHF+.  Is this choke idea an appropriate path to follow or should I suggest
> something else entirely?  Alternatively, are there any manufacturers of RF
> hardened AFCIs?
>
> 73,
>
> -Jeff
> W7WWA
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