# Antenna & Earth=Potential Difference?

Discussion in 'Physics' started by ross, May 14, 2012.

1. ### ross Thread Starter Member

Jul 30, 2010
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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.

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
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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3. ### MrChips Moderator

Oct 2, 2009
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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!

4. ### russ_hensel Distinguished Member

Jan 11, 2009
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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.

5. ### Papabravo Expert

Feb 24, 2006
10,338
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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.

6. ### ross Thread Starter Member

Jul 30, 2010
46
0
I don't understand do you have any references that I could look up?

7. ### ross Thread Starter Member

Jul 30, 2010
46
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Ah! so that's why we aren't plugged into towers,you couldn't have explained it better.Thankyou.

Jan 11, 2009
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