Seems pretty simple to me. You just need a more
efficient antenna on the receiver. I'd suggest a long
wire cut for 18.7 khz (1/2 wave is about 25,000')
strung around the property. Then use a strong metal
leash on the dog to act as a feedline, of course. 

He can roam the property always in contact with the
antenna, enjoying excellent reception from that
Harmon-Kardon transmitter.

Eric
KE6US

--- KY1K <ky1k@pivot.net> wrote:
> Hi All,
> 
> Yes, I have searched the archive:>:
> 
> Does anyone have any experience with the petsafe
> instant fence, 
> www.petsafe.net, model pif-300.
> 
> I bought one and was surprised to learn it was an
> audio amp feeding several 
> large air wound inductors with the output at 18.7
> Khz. I used spectrum lab 
> to gather the spectral info and found the schematic
> of the transmitter on 
> the web. The output spectrum looks like the
> transmitter is FM, which seems 
> odd to me.
> 
> I've gathered quite a bit of technical info on the
> transmitter, but the 
> receiver (on the dogs collar) remains a mystery.
> 
> I need to expand the range, building a more
> sensitive receiver seems to be 
> practical (using the same transmitter).
> 
> Anyone have any experience with these sort of
> systems? Let me know if you 
> want further technical info, I'll gladly send you
> what I have.
> 
> Thanks,
> 
> Art
> 
> 
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