Don,
Our invisible fence is the typical 10khz variety, but I found a 3 layer
approach worked well... each did a bit of reduction, and together it was
enough. Maybe that multi layer approach can help you.
- an FT240-31 on the wallwart cable... on the DC portion going to transmitter.
This reduces harmonics backfeeding into the house wiring. In this case
ferrites on the AC side didn’t make much difference, YMMV.
- i put a ferrite on each leg of the fence wire near the transmitter. I used
1/2” snap-on group 31 with as many wraps as I could fit. This reduces
harmonics on the fence wire.
- we were able to turn down the gain knob on the fence transmitter quite a bit
and it will still trigger the collar. Less transmitter power = less RFI.
Hope that helps,
Joe K1VW
> On Jan 23, 2022, at 10:23 AM, Don Kirk <wd8dsb@gmail.com> 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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