[RFI] Not your typical invisible fence RFI

Don Kirk wd8dsb at gmail.com
Sun Jan 23 13:05:01 EST 2022


Hi Tony,

Yes, I remember your case.  I'm the one that told you about the 10VK6 back
in 2016 per a recommendation I had received from the Innotek engineering
department.

73,
Don (wd8dsb)

On Sun, Jan 23, 2022 at 12:56 PM <tony.kaz at verizon.net> wrote:

> Had a problem  with the next door neighbor's inground dog fence. Wiped me
> out on 160M with a receive antenna within 10' of the buried wire. Provided
> a Corcom 10VK6 filter to the installer of the dog fence. It was put between
> the output of the transmitter and the underground wire. It got rid of the
> interference for 6 years now.
> N2TK, Tony
>
>
> -----Original Message-----
> From: Joseph Bouchard <joek1vw at gmail.com>
> To: Don Kirk <wd8dsb at gmail.com>
> Cc: RFI <rfi at contesting.com>
> Sent: Sun, Jan 23, 2022 11:41 am
> Subject: Re: [RFI] Not your typical invisible fence RFI
>
> 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 at 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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>
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