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No way. If that's true, I'll eat my hat. (let's see how that translates... :? )
j.
Well, wait a minute... do you mean like broadcast radio? Or like standing in front of the radar on a ship? Because you can cook a hot dog (or yourself) with the latter.
glebka11, is this the statement you are referring to?
I have not really been following this thread, but why not just use a one transistor radio receiver circuit and rectify the received wave with a diode to use it as a power source. (radio waves are everywhere). You should be able to get about 3 volts from this.
You then only have to connect it to a low draw bulb or LED.
Using a transistor in this context implies amplification, and the author doesn't mention the power source for the transistor. You can generate a few micro-amps at a few tenths of a volt from broadcast radio waves, and it's enough to drive a high impedance (crystal) headphone. The power "collected" from an unpowered receiver is several orders of magnitude less than what's needed to drive even the highest efficiency LEDs.
Using a transistor in this context implies amplification, and the author doesn't mention the power source for the transistor. You can generate a few micro-amps at a few tenths of a volt from broadcast radio waves, and it's enough to drive a high impedance (crystal) headphone. The power "collected" from an unpowered receiver is several orders of magnitude less than what's needed to drive even the highest efficiency LEDs.
I have read the all thread, by "one transistor radio" he meant a simple radio and then I didn't quite get it what he really meant
Anyhow the idea is to pickup signal with an antenna, rectfy and charge a cap. Could the 50Hz radion in our homes really be enough? sounds quite improbable. Nobody ever done anything like this?
It's certainly possible - but only under the correct circumstances.
You need to be very close to an extremely high power transmitter, by using a suitable tuned circuit you can tap power from it's radiation.
I've never known if it was just a story or not, but the story goes that a long time ago there was a very high power (multi-megawatt) VHF radio transmitter in Germany. The transmitter was sited on a hill, as they often are, and to one side was a nice long fertile valley. In this valley were many farms, and a lot of these farms had large greenhouses, which are commonly kept warm to extend the growing season.
One of the farmers discovered that by making a certain metal shape (which happened to be tuned to the correct frequency) he could provide free heating for his greenhouse.
Other farmers soon copied him, and eventually the broadcasters had complaints of poor coverage, but only in one direction - eventually they found it was due to heating all the greenhouses!.
I've never known how true the story is, but it certainly sounds possible!.
I doubt that many of these greenhouse farmers are still alive if there was THAT much radiated power, enough to be used for heating. :wink:
What does work, if one is close enough to a high power transmitter (or a multi KV power transmission line), is connecting a fluorescent light to the end of a long, stretched out, insulated wire and have it light up. One needs to be careful here, the voltage induced in the wire could give a very nasty electric shock.
What does work, if one is close enough to a high power transmitter (or a multi KV power transmission line), is connecting a fluorescent light to the end of a long, stretched out, insulated wire and have it light up. One needs to be careful here, the voltage induced in the wire could give a very nasty electric shock.
Recently there's been an 'artist' on the TV news, he planted a huge number of fluorescent tubes stood up in the ground under high voltage pylons, creating a pattern of weakly illuminated rods.
I think the second post by John S. put things in perspective. Of course you can light up bulbs or fluorescent tubes in the presence of a strong enough electromagnetic field, ask any radio amateur. Looking over the thread glebka11 referenced, the question appeared to be - can enough power be extracted from ordinary broadcast radio waves to light up a LED? "It depends where you're standing" is a correct, but not very helpful, answer. Being able to power a crystal headphone vs. lighting up a LED is comparing apples and oranges.
By all means glebka11, build & experiment. There's no harm in trying, though you may be disappointed with the results. If your LED or bulb does light up, I'd consider moving .
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