Hi Scott,

I suspect you are making it more complicated than it is. I have the
schematic for the transmitter, which is the part that stays indoors
and needs AC line power.

The only receiver is the receiver in the collar.

There has to be some logic in the collar though because it has to
initialize (won't issue corrections unless it hears the transmitter
when the receiver is first turned on).

After the collar is initialized, it will not issue corrections if the
dog (somehow) gets outside the 90 foot area and tries to re-enter.
This means that once the collar loses the signal completely, it won't
issue a correction when the collar acquires the signal again.

If the transmitter is powered down completely (after proper
initialization) the collar will not issue a correction either.

So, it's a smart receiver and is well thought out. But, all these
functions can occur as the result of logic contained within the collar
mounted receiver.

Last night, I looked at the signal using spectrum lab's vlf receiver
program. When I zoomed in on the transmitters signal, I noticed that
there were sidebands occurring every 15 hz. I will post another
message with more details.

A


PS..................

The vlf transmitter frequency is around 17 Khz. At first, this seemed
like an odd choice for a wireless fence.

But, I've done much research into vlf, and hte frequency selection
makes much more sense now!

VLF is used because the signal penetrates the ground better, meaning
that the received signal strength doesn't vary much if the dog goes
swimming or during a rain storm. Also, the signal strength changes
very little if the dog tries to crawl 'under' the fence. The signal
strength stays about the same if the dog turns towards or away from
the transmitter as well.

It also doesn't matter whether the dog walks behind a tree or
obstacles such as small buildings, dog houses or trash cans.

Because the wavelength is so long, these obstacles don't impact the
field strength much. A vhf/uhf transmitter would have very serious
drop outs with these types of obstacles.








It must be
simpler and then I would think they would use something other than 17
KHz....interesteing!!