Re: vlf transmitter, part II

Albert wrote:

This morning, I put my 17 Khz vlf transmitter (petsafe wireless fence)
on spectrum lab running on my laptop. What I saw has put me in a
tailspin.

I have the schematic and the screen captures showing the output
spectrum for anyone who wants to email me,  aballen at colby dot edu.

Using spectrum labs built in vlf receiver and a short antenna wire, I
was able to display the output spectrum of the transmitter without any
problems. BUT, I'm at a loss to explain the output spectrum.

Around 18 Khz, there is a peak. Exactly 15 Hz below and above the peak
is a smaller set of peaks, presumably these are the sidebands that the
receiver recovers. BUT, there is a peak every 60 Hz that slowly gets
weaker as the spectrum moves away from the (center) largest peak. Each
one of these smaller peaks has upper and lower sidebands as well.
There are many of these peaks, not just a few.

I wish I could attach the gif's and the schematic diagram of the
transmitter, but I think binary attachments are forbidden here.

For those who didn't read the original post, here's a summary. I
purchased a petsafe PIF-300 wireless fence to make an invisible fence
to contain our dog. The unit has a 17 Khz transmitter that runs in the
house from ac power. The small battery powered receiver is mounted on
the dogs collar and gives an audible warning and a correction IF the
dog tries to go past the transmitters range.

The url for the product is at:

http://www.petsafe.net/pet_containment/instant_fence.htm

Here's my question...

Why would they use a transmitter with such a wideband output and
containing so many spurs? Is there any kind of simple receiver that
can properly recover the transmitter?

As I said before, send me an email and I'll be happy to forward the
schematic and the screen captures showing the output spectra.

A 
sounds like power supply ripple getting into the Tx.
 also, you could be getting some grounding effects in your soil that
is getting carried with it from your Electrical service of your home.

 these are just a guess.

.

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