Scott,

Your question brings much complication to a matter that should be easy
to answer. I'll do my best to avoid getting bogged down in the
explanation.

The transmitter has a very long range, much longer than 90 feet. I
believe the dogs collar hears the signal for a very long distance.
But, that the collar does not issue a correction if the dog wanders
past the range of the transmitter. If the collar acted in this manner,
it would preclude the dog from RE-ENTERING the protected area from the
outside of the 90 foot range.

In order for the collar to initialize, it must hear the transmitter
(initially). If the transmitter is turned off, and the collar is
turned on, no corrections are issued.

Also, if the collar is properly initialized and operating, abruptly
turning off the transmitter DOES NOT result in a correction being
issued. Corrections are only issued IF the dog is in the intermediate
zone, which appears to be a 3 foot wide area.

This type of operation is necessary to safeguard the dog, even though
it complicates the hardware some.

At 16 kilohertz with horrendously inefficient transmitting antennas, I
doubt there would be an FCC problem, especially with a modest boost in
ERP. The Earth and the solar system generates much noise on those
frequencies as well, we could probably increase the transmit power
quite a bit without creating problems.

Hope this helps.

A



On Tue, 29 Mar 2005 12:09:27 +0000, Scott
wrote:

I auume these thing work in reverse of conventional thinking. I assume
that as long as the receiver is receiving a signal, the dog does not get
shocked. If it strays too far and the receiver loses the signal...ZAP!
However, modifying the transmitter would violate its Part 15
certification and the owner might be the one to get the ZAP (from the
FCC)...

Scott

Ahhh! Then there must also be a transmitter in the collar to "answer
back" to the stationary transmitter? If so, maybe the thing works on
the amount of time calculated for the signal to travel round trip. A
radar mile (2 miles round trip) is about 12 microseconds, if I recall.
Rountrip at 90 feet would be something like 183 nanoseconds. If THIS is
how the unit works, running a kilowatt wouldn't make a difference. It
would require changing the interval time that the transmitter waits for
check-back. Maybe I'm making this too complicated It must be
simpler and then I would think they would use something other than 17
KHz....interesteing!!

Scott


Albert wrote:

Scott,

Your question brings much complication to a matter that should be easy
to answer. I'll do my best to avoid getting bogged down in the
explanation.

The transmitter has a very long range, much longer than 90 feet. I
believe the dogs collar hears the signal for a very long distance.
But, that the collar does not issue a correction if the dog wanders
past the range of the transmitter. If the collar acted in this manner,
it would preclude the dog from RE-ENTERING the protected area from the
outside of the 90 foot range.

In order for the collar to initialize, it must hear the transmitter
(initially). If the transmitter is turned off, and the collar is
turned on, no corrections are issued.

Also, if the collar is properly initialized and operating, abruptly
turning off the transmitter DOES NOT result in a correction being
issued. Corrections are only issued IF the dog is in the intermediate
zone, which appears to be a 3 foot wide area.

This type of operation is necessary to safeguard the dog, even though
it complicates the hardware some.

At 16 kilohertz with horrendously inefficient transmitting antennas, I
doubt there would be an FCC problem, especially with a modest boost in
ERP. The Earth and the solar system generates much noise on those
frequencies as well, we could probably increase the transmit power
quite a bit without creating problems.

Hope this helps.

A



On Tue, 29 Mar 2005 12:09:27 +0000, Scott
wrote:


I auume these thing work in reverse of conventional thinking. I assume
that as long as the receiver is receiving a signal, the dog does not get
shocked. If it strays too far and the receiver loses the signal...ZAP!
However, modifying the transmitter would violate its Part 15
certification and the owner might be the one to get the ZAP (from the
FCC)...

Scott

Nothing but a little receiver and a buzzer in the belt. The wire
radiates and the lil bitty receiver detects it and the little dog
regrets his closeness to his boundaries.

Butch

Scott wrote:

Ahhh! Then there must also be a transmitter in the collar to "answer
back" to the stationary transmitter? If so, maybe the thing works on
the amount of time calculated for the signal to travel round trip. A
radar mile (2 miles round trip) is about 12 microseconds, if I recall.
Rountrip at 90 feet would be something like 183 nanoseconds. If THIS is
how the unit works, running a kilowatt wouldn't make a difference. It
would require changing the interval time that the transmitter waits for
check-back. Maybe I'm making this too complicated It must be
simpler and then I would think they would use something other than 17
KHz....interesteing!!

Scott


Albert wrote:

Scott,

Your question brings much complication to a matter that should be easy
to answer. I'll do my best to avoid getting bogged down in the
explanation.

The transmitter has a very long range, much longer than 90 feet. I
believe the dogs collar hears the signal for a very long distance.
But, that the collar does not issue a correction if the dog wanders
past the range of the transmitter. If the collar acted in this manner,
it would preclude the dog from RE-ENTERING the protected area from the
outside of the 90 foot range.

In order for the collar to initialize, it must hear the transmitter
(initially). If the transmitter is turned off, and the collar is
turned on, no corrections are issued.
Also, if the collar is properly initialized and operating, abruptly
turning off the transmitter DOES NOT result in a correction being
issued. Corrections are only issued IF the dog is in the intermediate
zone, which appears to be a 3 foot wide area.

This type of operation is necessary to safeguard the dog, even though
it complicates the hardware some.

At 16 kilohertz with horrendously inefficient transmitting antennas, I
doubt there would be an FCC problem, especially with a modest boost in
ERP. The Earth and the solar system generates much noise on those
frequencies as well, we could probably increase the transmit power
quite a bit without creating problems.

Hope this helps.

A



On Tue, 29 Mar 2005 12:09:27 +0000, Scott
wrote:


I auume these thing work in reverse of conventional thinking. I
assume that as long as the receiver is receiving a signal, the dog
does not get shocked. If it strays too far and the receiver loses
the signal...ZAP! However, modifying the transmitter would violate
its Part 15 certification and the owner might be the one to get the
ZAP (from the FCC)...

Scott

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!!

On Wed, 30 Mar 2005 08:31:08 -0500, Albert wrote:
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.

Hi Albert,

This could be an ID modulation to serve the receiver's logic. In
other words, correction is based upon both signal strength AND
modulation.

Thus the received signal strength has to fall to a certain level that
is still above noise level (not complete drop-off) to insure that
corrections are not applied due to power failure at the transmitter
(and to allow registration at power-up).

VLF is used because the signal penetrates the ground better,

This was what I described as the subterranean communications channel
used in the trenches of WWI. I would still suggest a power boost over
building a ground dipole. The design of the amp is trivial, and kits
are available to do the job for less than $20.

73's
Richard Clark, KB7QHC

This could be an ID modulation to serve the receiver's logic. In
other words, correction is based upon both signal strength AND
modulation.


I think it's even simpler than that... It could be based on the signal
strength alone.

As long as the received signal is treated in an analog manner, it
would be easy to tell the difference between a strong and a moderately
strong signal. I'd bet they don't do anything as sophisticated as a
digital decode to identify the transmitter.

Be on the lookout for 'vlf transmitter, part II.......coming to this
newsgroup soon. Basically, I ran the transmitter into a spectrum
analyzer and saved the output spectrum of the transmitter. It's very
interesting and leads to another whole set of questions.

Regards.

A

On Wed, 30 Mar 2005 18:09:13 -0500, Albert wrote:
This could be an ID modulation to serve the receiver's logic. In
other words, correction is based upon both signal strength AND
modulation.

I think it's even simpler than that... It could be based on the signal
strength alone.

Hi Albert,

Given the features you've imputed to the design, transmitter drop out
(loss of AC power) would be indistinguishable from puppy border
crossings.

Or, yes, it could be signal strength alone (still argues for a simple
Amp any 'splanation considered).

Part Deux of the mysteries of the VLF is looked forward to.

73's
Richard Clark, KB7QHC