[RFI] Looking for explanation...

[Grant Saviers]

Any surge protectors on the problem circuit?  Degraded MOV's can cause 
problems.  GFI outlets also.

Grant KZ1W

On 6/26/2020 10:30, Gary Peterson wrote:
> Periodically, I have been plagued with RFI from an unknown source.  It sounds like a washing machine, as far as the cadence is concerned, with a swish, swish, swish sound.  It will show several tracks on the 80 meter waterfall.  It will end abruptly.  Every previous time it has come on, it has quit before I could get to my gear together and DF it.  I had my equipment ready to go and when it came on and I dropped what I was doing and went outside.  My loop gave me a beautiful, deep null toward the neighbors house, about 300 feet away.
> 
> I gave my neighbor a call and told him what I discovered and asked him if he had been running any appliances a few minutes earlier.  He told me his main squeeze had been on the treadmill.  My neighbor is a ham, who has not been active for about a decade.  He turned on the treadmill and there it was!  Source found.  The treadmill is a PowerTread, I was told.
> 
> I gave him an EMI filter to try, that I had found in a box of assorted electronic parts purchased some time ago.  The filter is a TDK, model ANF-106U.  My neighbor plugged it into the outlet and plugged the treadmill into the EMI filter.  The filter knocked the RFI down by a couple of S units, but I could still hear the swishing.  Next, he plugged the treadmill, via an extension cord, into a different outlet, without the EMI filter.  No interference whatsoever was heard or seen on the waterfall.
> 
> Is it possible that the wiring from the nearest outlet, back to the service panel, is resonant on 80 meters?  Or, is it more likely that a connection might need tightening in the outlet box or breaker panel?  He does not know whether the troublesome outlet and the good outlet are on the same circuit or not.  I had him check both outlets with an outlet tester, thinking that he might have a mis-wired outlet.  Both checked OK.  He is afraid to get into the troublesome outlet box or his electrical panel.  I volunteered, but he doesn’t want me to take the risk.  When I was in broadcasting full time, I was inside more electrical panels than I can count, but I respect his wishes.  Before I hire a licensed electrician to check my neighbor’s wiring, I would like to have a better handle on the probable cause.
> 
> Any thoughts as to the explanation for this rather odd behavior will be most appreciated.
> 
> Gary, K0CX
> 
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