In article ,
wrote:

If you do you will be in violation of several laws regarding harmful
interference.

Well then I imagine that every rancher with an electric fence must be
repeating Marconi's experiment as well. And what about the computers in
the area that break the squelch on my low band radio in my truck as I
drive past the same houses. And not to mention those infernal speed
controlers and light dimmers that raise hell with AM radio. MJy friend
is just trying to keep coons out of his garden. How do these guys get
away withit. Lenny

They don't use a spark-based generator.

I looked at a few of the schematics out there on the net, and a lot of
them seem to use a low-voltage astable multivibrator (e.g. a 555) to
trigger a triac, which dumps a pulse of chrarge from a capacitor
(e.g. a couple of hundred volts) into the primary of a step-up
coil. The coil then drives the fence wire.

This approach would (I think) result in the rising and falling edges
of the current pulse into the primary not being incredibly fast... the
rising edge would be limited by the coil inductance, and the falling
edge would result from the stored-up charge in the cap damping down -
there's be some ringing to the latter, but not the sharp edges you'd
see from a spark gap. Hence, a lower bandwidth and less (or no) RF
interference.

Commercial cow fences usually seem to pulse once a second or so - it's
not a constant buzz. It's enough to displease the cows (and probably
deer as well), but it's not continuous enough to risk that somebody
will grab the wire and find themselves unable to let go (which would
be a real risk if you just let a vibrator drive a coil and keep the
wire energized all of the time).

People *do* get in trouble with the FCC over electric-fence
chargers, if the chargers are badly designed and do result in RFI.
The fines for failing to correct such sources of interference can be
quite stiff.