[RFI] Not your typical invisible fence RFI

[Pete Smith N4ZR]

Hi Don - Interesting! Years ago, when I got my first Invisible-Fence 
brand system in my old house, I wondered if it would be a problem, but 
was told that the underground loop operated at around 17 KHz.  I was 
never able to pin any interference on it, either in my old house or in 
this new one, with a 1000-foot underground loop.  It sure sounds like 
there's something in the fence driver in your neighbor's house that is 
putting out the RFI. Incidentally, your neighbor's fence drive looks 
nothing at all like mine - maybe there was a design change inside it as 
well.

73, Pete N4ZR
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On 1/23/2022 10:23 AM, Don Kirk wrote:
> I just uploaded a video onto YouTube that documents wideband RFI on 20
> meters that I tracked down to my neighbors invisible fence transmitter, and
> it's not the typical approximate 7 or 10 KHz interval RFI encountered with
> inground invisible fences.  The RFI which is at least 150 KHz wide at my
> house moves around based on outdoor temperature and on warmer winter days
> it drops down to slightly below the 20 meter band.
>
> I was hoping the problem was with the wall-wart power supply feeding the
> transmitter but it was not.  The transmitter has battery backup and the RFI
> is still present with the wall wart unplugged, and we also tried a linear
> lab grade power supply in place of the 19.0 Vdc 1 amp wall wart with no
> noticeable difference in the level of RFI at my house.
>
> Unfortunately the transmitter is not part of a DIY system so the
> manufacturer (Radio Systems Corporation) requires that we deal with the
> local "Invisible Fence" Dealer which is our next step.
>
> An interesting note is that when I first tracked the RFI down to my
> neighbors home I wound up near the main circuit breaker box.  We then tried
> sniffing the circuit breakers with a very small loop to see what circuit in
> the house the RFI was originating (assuming the RFI was being conducted on
> house wiring) and this technique typically works great.  We did not detect
> the RFI on 20 meters on any of the circuit breakers which was interesting
> because the RFI was strong near the main circuit breaker box.  It turned
> out that the invisible fence transmitter is just a few feet away from the
> main circuit breaker box which explained why the signal was strong near the
> main circuit breaker box.
>
> For those interesting here is a link to the video documenting the RFI:
> https://youtu.be/rHABjR0GZWg
>
> P.S. I have great neighbors that are wonderful to work with on RFI issues.
>
> 73,
> Don (wd8dsb)
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