| Author | Message | ||
     G |
I saw that your simple radio set up lights the LED you use for a diode which got me thinking. If a wall of antennas were in line of sight of a high power transmitter could u trickle charge a battery with the recieved power. And have a reversed diode line to collect other half of energy like a full wave rectifier. Also am I right in saying that a solar pv cell is analogous to a radio reciever as light is a very short wave radio signal? | ||
| Simon Quellen Field (Sfield) |
The amount of power I get from a 500 foot wire antenna and a good ground is about a milliamp at 1.2 volts, or a hair over a milliwatt. You could get much more power from one of our tiny solar cells, for less than the cost of the 500 feet of wire. And it wouldn't even need direct sunlight, just enough light to read by. The photoelectric effect is a quantum effect, unlike what happens in an antenna. In an antenna, the radio wave induces a current in the wire, and that current is then rectified by a diode. In a solar cell, a photon of light knocks an electron off of an atom, creating a free electron and a positively charged space in the crystal where the electron used to be, called a hole. The two dissimilarly doped parts of the solar cell create an electric field, so the free electron and the hole move in opposite directions under the influence of the electric field. The current thus produced is the output of the cell. One of the ways this difference makes itself apparent is that with an antenna, the more energy there is in the radio wave, the more energy you get out. In a solar cell, higher energy light waves (blue or ultraviolet light) do not produce more energy than red light. The extra energy turns into heat, and is lost. This is why the very high efficiency solar cells used in satellites have two or more semiconductors -- one for the low energies, and another for the higher energies. | ||
| G |
I viewed the colors of light being analogous to the different carrier frequencies in radio. To me the energy (intensity) of light is analogous to the amplitude of radio signal. A satellite dish antenna to me is analogous to a fresnel lens on a solar cell. So I thought the different semiconductors used in satellites are analogous to different taps. But based on Einsteins photelectric theory u r right! ie frequency determines energy in the case of light not amplitude! | ||
| Christopher Schmidt |
Simon you were only resonating with one radio station correct? what if you were able to resonate with all radio stations across the band? 1.2 volt at like 20ma?now thats some substantial power, possibly to charge 1 farad super capacitors?and with a flashing circuit it probably could last a few hours powering an LED at full brightness! please explan if and how this could be done. Thank You | ||
| Simon Quellen Field (Sfield) |
In order to resonate with all frequencies, you will need a resonant circuit for each frequency. The nature of resonance is that it can only happen at one frequency. But since coils and capacitors are cheap, you could simply build a crystal radio for each frequency, and connect the outputs together. If you just want free power, however, a cheap solar cell will generate much more electricity. | ||
| Chris Schmidt |
Simon, How would I go about this? Can I use one antenna for all the crystal sets? Also what would be the simplest way to do this as fare as the "set up" goes? I looked at your coil calculator and from what I gather, I could just make a few coils out of paper towel cardboard spools cut to the right size and coil Radio Shack 26g magnet wire around it. Then put all nessasery components inside the coil? I would hook them up in series/paralell to get desired voltage/ current? I know solar panals ect.... would work better but I just want to see how much power I can get from radio. Please tell me as much as possble! Will 200 feet of 30g wire 30ft off the ground be enough for an antenna? Thank You ^_^; | ||
| Simon Quellen Field (Sfield) |
You want to get as much power as you can get from radio. You could put the radio in the microwave. The proximity to the high power transmitter would generate several watts. How much you get from a commercial AM radio station will similarly be affected by proximity, the wattage being transmitted, and the size of the antenna. Tuning the circuit to 60 hertz will probably produce the best effect. The transmitter is both very powerful, and close. You would need a separate antenna for each frequency. The radio selects a frequency by connecting all other frequencies directly to ground, and sending the chosen frequency to ground by way of the earphone. If you had two crystal sets on the same antenna, tuned to different frequencies, I would expect each one to have diminished output, because the other set was providing a short circuit to ground for the frequency this set wanted to hear. But just how much loss you would get is unclear to me from first principles -- I would have to do the experiment and measure. The longer the antenna, the more power it will intercept, other things being equal. | ||
| Chris Schmidt |
I have a few towers near my location, 50,000 watts 13 miles away in NYC. I also have a cell phone antenna about 1/4 mile away, and a bunch of these 500 foot tall red and white colored antennas about 5 miles away. The 50 kilowatt antenna I beleave is on top the Empire State Building, witch is near enough to see directly if there were no trees. Now for the questions! Can I make one untaped coil for each frequency, could I put my antenna on a branch 30 feet high and coil from the groung back to the branch 6 times to get the length I need(I dont want to take birds out of the sky like WW2 anti aircraft ballon cables), and finaly, can I make the coils for the radio a little off so they pick up the same station put are on differant frequencies? Thank You. | ||
| Simon Quellen Field (Sfield) |
Sounds like time to do the experiment. Just set it up and see what you get. I am not sure what you mean by "the same station but different frequencies". A station transmits on a single frequency. If you have two crystal radios sharing an antenna, but tuned to different frequencies, you will not pick up either frequency well. | ||
| Aleksandar |
I think Collecting radio energy is illegal... I think.. | ||
| Simon Quellen Field (Sfield) |
Nope. Perfectly legal. Otherwise you couldn't listen to the radio. | ||
| dharma one |
"In a solar cell, higher energy light waves (blue or ultraviolet light) do not produce more energy than red light. The extra energy turns into heat, and is lost. This is why the very high efficiency solar cells used in satellites have two or more semiconductors -- one for the low energies, and another for the higher energies. " here is a novel way to prevent the extra energy from being converted to heat, and make it move more than one electron at the time http://www.trnmag.com/Stories/2004/051904/Solar_crystals_get_2-for-1_051904.html | ||
| Simon Quellen Field (Sfield) |
Yes, I saw that when it came out on "http://worldwatts.com". Now to find a way to make a non-toxic version of those nanoparticles in my kitchen... | ||
| MadScientist (Madscientist) Advanced Member Username: Madscientist Post Number: 72 Registered: 4-2005 |
Light pulses only 50 femtoseconds long? Not that I'm really doubting it, but how do you measure something that short? Technology is flat out amazing, eh? | ||
| Red Dragon (Red_dragon) New member Username: Red_dragon Post Number: 3 Registered: 4-2007 |
I have wanted to try to get free power from radio waves. I'm live in SC and I got a AM radio station near by. can some help me do it | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1812 Registered: 12-2004 |
Build a crystal radio, and replace the earphone with an LED. |
