# Antenna & Earth=Potential Difference?

#### ross

Joined Jul 30, 2010
46
If I put up a big antenna and drove a copper pipe deep into the ground, What kind of potential difference would I get? Would it be enough to be useful? If it is feasible at what scale? Ive always wondered about the physics of this.

#### t_n_k

Joined Mar 6, 2009
5,455
This big say?

http://en.wikipedia.org/wiki/KVLY-TV_mast

The electric field strengths near powerful transmitter masts can get quite high - >100V/m or more within a few meters of the tower. The (near field) electric field strength reduces dramatically as the distance from the tower increases. Even with a very large receiving antenna carefully tuned to the transmitter frequency you would be unlikely to get a useful voltage source a few kilometers from the transmitter.

I've heard a claim that some people have been known to steal RF energy using tuned circuits in their homes in close proximity to a radio transmitter. It's illegal to do so.

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#### MrChips

Joined Oct 2, 2009
22,056
We were pulling up a 14' sailboat (Albacore) on to the beach under some HV transmission towers. If you touched the mast or stays (guy wires) on the sailboat you got a shock!

#### russ_hensel

Joined Jan 11, 2009
825
The earth and atmosphere also have a ( near DC ) field, can be many volts per meter, but at a high impedance so collecting energy is low until it is hit by lightening.

#### Papabravo

Joined Feb 24, 2006
14,647
Think High Voltage e.g. several hundred volts at miniscule currents e.g. nanoamperes. The power output of an antenna is very small on the order of microwatts.

#### ross

Joined Jul 30, 2010
46
The earth and atmosphere also have a ( near DC ) field, can be many volts per meter, but at a high impedance so collecting energy is low until it is hit by lightening.
I don't understand do you have any references that I could look up?

#### ross

Joined Jul 30, 2010
46
Think High Voltage e.g. several hundred volts at miniscule currents e.g. nanoamperes. The power output of an antenna is very small on the order of microwatts.
Ah! so that's why we aren't plugged into towers,you couldn't have explained it better.Thankyou.

#### russ_hensel

Joined Jan 11, 2009
825
I don't understand do you have any references that I could look up?