Hi Joe and gang,
Thanks for the comments.
I'm not looking for a home brew solution as I already know what a solution
is based on my past experiences with invisible fence systems including my
own. As I mentioned the problem with the invisible fence I'm currently
dealing with is not the typical problem of repeating intervals of the
primary transmitted signal (normally between 7 and 13 KHz) that's the
normal problem with invisible fence systems, but rather a very broad non
modulated signal in the 20 meter band.
Numerous years ago I actually designed and built my own invisible fence
transmitter to mimic the Innotek in ground system that I was already using
because I wanted another transmitter to work with my dogs collar in a
secondary location on my property but was to cheap to buy another
transmitter. I generated a 8.17 KHz PWM Signal using a Microchip 16F690
microcontroller that transmits a 8 bit code; Code = 01010101 where 0 is a
short pulse and 1 is a long pulse, and this mimicked the signal transmitted
from my store bought transmitter and works great. On both my store bought
and home built transmitters I designed and installed a balanced low pass
filter that connects to the output of the transmitter (between the
transmitter and in ground wire loop), and this solved all my problems of
repeating intervals of the 8.17 KHz signal and it should also work on my
neighbors system but I really want the Invisible Fence company to see
what's happening as the problem might actually be an abnormal transmitter
since it's atypical of anything I have ever encountered with invisible
fence transmitters. I would prefer a low pass filter solution from
Invisible Fence versus my own from a liability standpoint and hope that's
what we wind up with unless replacement of the transmitter also solves the
problem.
73,
Don (wd8dsb)
On Sun, Jan 23, 2022 at 11:41 AM Joseph Bouchard <joek1vw@gmail.com> wrote:
> 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)
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
>
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