*Note from author: Please do not try this experiment without a thorough knowledge of electricity! Please understand that it is illegal to take power from power lines. This is an experiment only.
The following article was contributed by Mark Vess.
If you run a single wire along a high voltage power line, (= or> 340KVAC), you will harvest a fair amount of voltage at micro amp levels. WARNING: KEEP AT LEAST 30 FEET FROM THE HIGH VOLTAGE LINE!! DO NOT DO THIS EXPERIMENT ON WINDY DAYS!! The longer the parallel wire, the higher the voltage and amperage you can collect.
Run your (antenna wire) parallel to the power line in the trees adjacent to one outer phase of the power line. The higher the wire, (antenna), the better. Use small gauge bare wire hung from fishing line for insulation and support. Run at least 200 feet of bare antenna wire. 400 feet equals twice the power collected. Use a fishing pole and weight to put up the wires in the closest branches of the trees next to the HV line.
WARNING, DO NOT TOUCH THE ANTENNA WIRE! YOU WILL GET SHOCKED! I recommend two pairs of rubber gloves and good boots for this. Ground the antenna wire while you work until the transformer (s) are installed and you are ready for power. Provide a single or several 5-foot copper-plated ground rods at your termination point for the transformer high voltage return to ground. More grounds are better. The ground completes the high voltage antenna circuit.
The trick is to present a minimum load to the antenna wire and to step down the electrostatically induced voltage. We need a very high voltage transformer to do this. A ham radio plate transformer rated at 10,000 volts works well. Neon sign transformers work well. You can use several used oil burner transformers with the secondary in series.They are 10 KV each so you can make a 50 KV secondary with five of them. Much better!
Remember, the higher the transformer ratio from the high side to the low side of the transformer, the better match you will have to the source (the power line antenna). We then connect the high voltage transformer secondary (HV) winding to the antenna and the ground.
Separate transformers MUST have the 120-volt leads in parallel and IN-PHASE. You have created a capacitive-coupled step-down transformer. Place a 4-watt, 120-volt light across the 120-volt terminals of the transformer. If the light pops and you measure a higher voltage, you may add another single transformer to get to the voltage you desire from the HV transformer (s).
You need to measure the AC voltage out of the HV transformer primary and find a 120-volt transformer for that voltage. Example: 600 volts out requires a 600-volt secondary and a 120-volt primary. Place this step-down transformer after the HV transformer. You may also ground the far end of the antenna wire to create electromagnetic coupling to the power line. No other circuit changes are required for this. Bring along some different wattage/voltage lamps, a car battery charger, a small battery, and some small AC motors to see the power you have collected. Have fun!
Author: I am purposely not saying I ever did this. Work safely and remove the antenna when done so it will not blow into the high voltage power line.