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Could a cell phone charge its own battery from the cell tower signal?

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LAN_403

Austin the Ozone

Thu Dec 22 2011, 10:19AM

Registered Member #3989 Joined: Thu Jul 07 2011, 05:10PM
Location: In a van down by the river.
Posts: 52

I was watching a you tube video about crystal radios and thought of this. Is it possible? Sounds good, a cellphone with a battery that never run down as long as there is signal right? Here is the crystal radio http://www.youtube.com/watch?v=gcui0K7JZXA&feature=related

Steve Conner

Thu Dec 22 2011, 10:47AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Well, ponder the inverse square law and the implication that the phone's transmitted signal must be stronger than the one it receives from the cell tower.

Get a feel for some typical figures for path loss

to see just how much power the phone actually receives. (You can assume about 100W for the cell mast, but it wouldn't make much difference if you assumed 10 or 10,000.)

Then think about conservation of energy and the implications for duty cycle, talk time, and so on.

Patrick

Thu Dec 22 2011, 10:54AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

well if im thinking correctly that cell phone signals are basically omni-directional, then youd be screwed out of power by
inverse square law, so at long ranges (even short ranges) i think youd get negligable power. remember the per second power consumption of the phone would need to be less than or equal to your per second captured power. even with a large collecting antenna i think this is not really possible.

I have done many experiments with signal diodes (1n914) to detect radio waves, but i never got more than miliivolts and microamps. the little glass diodes are sensitive to light (like a solar cell), and in many cases i found the sun light to be more energetic than the radio waves in the San Francisco Bay Area for these glass diodes, and i was within sight of airport antenna, radio station and pager towers in the mid 90's.

better ideas i think, would be personal solar, or motion-energy recapture, so the movement of your body vibrates and bounces a magnet with motion that a coil recovers as electrcity.

Or a little hand crank generator for life and death type safety purposes.

just my thoughts...

EDIT: Steve McConner got in a ninja post LOL !

radiotech

Fri Dec 23 2011, 07:25AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

You could wind a coil and attach it to a tether and whirl it about. Rectify the
output. Be sure not to hit anyone with it, though..

For inspiration consider a sling psychrometer.

Just by waving a 'degausing' coil attached to galvanometer convinces people
that cutting the earths magnetic field, with a wire does create a current.

Then when this proves untenable, refine the design so the sling concept actually
operates a small generator.

Then build it into the cellphone. Arrange an app, using a gps locator to find the phone,
if you accidently let the tether go while charging the phone.

Tetris

Fri Dec 23 2011, 10:13PM

Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660

radiotech wrote ...

You could wind a coil and attach it to a tether and whirl it about. Rectify the
output. Be sure not to hit anyone with it, though..

For inspiration consider a sling psychrometer.

Just by waving a 'degausing' coil attached to galvanometer convinces people
that cutting the earths magnetic field, with a wire does create a current.

Then when this proves untenable, refine the design so the sling concept actually
operates a small generator.

Then build it into the cellphone. Arrange an app, using a gps locator to find the phone,
if you accidently let the tether go while charging the phone.

I can see the future now... *over hears people talking about how silly I am... lets go of tether* OW MY HEAD! Also.... there is an app for everything. There is even an app in development for measu... well I am not sure I should say it. But still, I don't think it will catch on. Unless its like a lanyard kind of thing. Then I don't think it can stop.

ShawnLG

Sat Dec 24 2011, 08:59AM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

This video should be a good explanation.

JohnL

Thu Dec 29 2011, 01:04PM

Registered Member #3842 Joined: Thu Apr 21 2011, 12:19PM
Location:
Posts: 10

even if it were possible, do you really think the greedy phone companies would let you get their broadcasted energy for free? They'd try to make people pay

radiotech

Fri Dec 30 2011, 08:11AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

One thing that could be done in this experiment is to see what the average broadband
energy level is when you are in a crowd of people all texting and talking at the same time.
That collective power level might be captured to specifically charge your cellphone. Just
a diode or bridge connected to a few yagis. Could this degrade the range of the group
of the phones?

Killa-X

Fri Dec 30 2011, 03:53PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Thing is, if you could pull enough energy on a cell tower, to charge the battery at a faster rate than its draining....What stops someone from just creating some kind of coil, that captures cell tower frequencies, and use it to power___ instead of using a cellphone? Thats my view as to why i dont see it too usable, if possible. Else people could manage a way to transfer radiowaves in the air, to usable power at home to power small devices -- or just charge them. would require a bit of power though.

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