Mike Y wrote:
And while I realizeit's quite possible to get 'shocks' off an
induction
coupling that essentially goes to a high impedance, it's a far cry from
being
able to 'power a house' with a broadcast transmitter that wasn't designed
for the purpose.

The original story that I heard about 40 years ago is
that it involved 60 Hz high-voltage power lines. A
farmer is supposed to have built an induction coil
in a shed directly beneath the power lines and picked
up free energy.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote in
:

Mike Y wrote:
And while I realizeit's quite possible to get 'shocks' off an
induction
coupling that essentially goes to a high impedance, it's a far cry
from being
able to 'power a house' with a broadcast transmitter that wasn't
designed for the purpose.

The original story that I heard about 40 years ago is
that it involved 60 Hz high-voltage power lines. A
farmer is supposed to have built an induction coil
in a shed directly beneath the power lines and picked
up free energy.



I've read that typically 1/3 of the current in a multiple ground
wye connected transmission system returns though the earth.
Seems a shame not to pass it though a few lightbulbs as it
passes by!

There was a story just a few years ago about a farmer that was
obtaining power from a fence running parallel to a transmission
line. He went to court and eventually won his case since this
power was already lost in the return resistance of the earth
and the power company failed to contain the current within their
transmission line. I can't recall what he was doing with it.

There was a room in the building of my last employer where no VDT
would function properly. We had a survey instrument in the EMI lab
so we gave it a try. The 60Hz magentic field in that room was intense.
We pulled down some ceiling tiles and found a large steel beam that
spanned the length of the building went to ground there. The beam
was parallel to the transmission line about 50ft just beyond the
outside wall. There was a substation was about 250ft away. I'm
sure the beam was grounded at both ends. Seems like the orientation
wasn't best for inductive coupling. Could have been carrying some
of the return current. A rough estimate of the current had it in the
hundreds of amperes. I can't account for it. Strange but true.

Later I heard from a former coworker who got a job with Super
Computers Inc then spent his first year mapping the "stray voltage"
at a site before they built their facility there. They found it can
cause problems with their process instrumentation.

Grumpy The Mule wrote:
Cecil Moore wrote in
:

Mike Y wrote:
And while I realizeit's quite possible to get 'shocks' off an
induction
coupling that essentially goes to a high impedance, it's a far cry
from being
able to 'power a house' with a broadcast transmitter that wasn't
designed for the purpose.
The original story that I heard about 40 years ago is
that it involved 60 Hz high-voltage power lines. A
farmer is supposed to have built an induction coil
in a shed directly beneath the power lines and picked
up free energy.

Hmm.. a bit of physics..

Induced voltage is Nturns*dPhi/dt
dPhi/dt - change in flux (Webers) per second

Flux is area of coil * B field.

AC field under a HV power line is typically around 1-10 microTesla.

So, the peak flux through a 1 square meter coil is about 10 microWeber.
At 60Hz, the maximum slope is 2*pi*frequency, or 377, so now, we're up
to 377*10E-6, or 377E-5 or 3.77E-3.. about 4 millivolts..

Now, lets assume a coil that's 10x10 meters.. that's 100 square meters,
so we're up to 0.4 volts, open circuit voltage, for one turn.

Now, let's say our ambitious farmer winds 100 turns.. now we're up to 40
Volts. But, that coil is 4000 meters of wire (100 turns * 40
meters/turn), and will have non-zero resistance. Let's say our farmer
used AWG 10 wire. about 1 ohm/1000 ft, so call it 13 ohms all told
(4000 m is approximately 13000 ft).

So we have a source with 40V open circuit output voltage and 13 ohm
output Z. If we hook up a matched load (another 13 ohms), it will have
20 Volts across it, and dissipate about 30 watts in the load and 30
watts in the loop.

Now, at $0.10/kWh, and 0.03kW, that's about $26/year

Of course, there's the labor in building that coil.
And, the cost of the wire. (400lb of copper at $3/lb is $1200)

Sure, you'd use aluminum wire, so you could cut that down by a factor of
3 or so.. So, invest a lot of hours stringing up that coil, and a few
hundred bucks in aluminum, and save $30/year...

Excellent economics there..