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Radiowaves to Electric waves

  1. Apr 8, 2009 #1
    Hey can anybody tell me if its possible to convert Radio waves to Electric signals?
  2. jcsd
  3. Apr 8, 2009 #2

    Andy Resnick

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    Sure- a radio reciever does a great job.
  4. Apr 8, 2009 #3


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    Or just an antenna.
  5. Apr 8, 2009 #4
    My Idea is to create a device which can receive radio signals, convert them into electric signals. This way one can conduct electricity wirelessly. What do you think of this?
  6. Apr 9, 2009 #5


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    I believe (outside of some limited and very low-power applications, or short-ranges) it will be particularly inefficient, and may result in a feeling of increased warmth (as your body is irradiated by the high-powered microwaves or radiowaves used to carry the power). On the upside, people will be stronger as their wirelessly powered devices will contain large and probably heavy induction coils. :smile:

    Not to bash the idea, but wireless electricity, and wireless power come up every so often in Physics Forums (you can find these by doing a search for wireless power or wireless electricity). For instance, the following:
  7. Apr 9, 2009 #6
    Hey Matlab dude, Thanks for those links. Im jus sad that we people with so much intelligence are still not able to find alternatives for the Tesla experiment without frying things. I hope one day that comes.

    My Idea was this. a transmitter wud be placed in a plug point which will send out the Radio waves. There would be a receiver connected to your device(such as cell phone, laptop etc etc). The transmitter sends out waves, the transmitter coverts waves to Electricity. The cell phone or laptop attached to the receiver wud be charged.

    I am a bio-technologist and have just started out my research in Nano-Sciences. I came up with the idea when i was day dreaming in my lab and posted this thing here.:cool:

    Now that i found out that i wil not be able to Patent this idea makes me sad... lol...:frown:

    Do youthink building a small transformer will help increase the votage andd hence the electricity received?
  8. Apr 9, 2009 #7


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    This is not exactly a new idea; it is essentially how RFID devices (used in e.g. buss passes and key-cards) are powered. There are also more "exotic" examples where people (well, NASA) have powered aircraft via a very intense microwave beam.
    Unfortunately it is a very inefficient methods of transferring energy, Another problem is that it is inherently unsafe since chances are that something else expect the intended receiver will pick up the signal. The fields would also have to be VERY strong meaning there would be all sorts of health&safety issues.
    So yes, the idea works but is just not practical for devices such as laptops etc.
  9. Apr 9, 2009 #8
    Thank you for the patient reply.
    I know all the examples that you have given. I'm just intrigued by the idea of charging devices wireless. could you be more specific bout the "using a Transformer to increase the voltage" issue.
  10. Apr 9, 2009 #9


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    Transformers will not do anything for you. All they can do is step up or down the voltage, they cannot change the amount of power delivered. If anything, they'll decrease the power due to various losses.
  11. Apr 9, 2009 #10
    Oh Ok

    but doesnt increasing the voltage also increase the amount of electricity in the component and hence resulting flow of electrons and thus power? Its been a long time since ive bin into Physics. Please help me out with this
  12. Apr 9, 2009 #11


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    No. Increasaing the voltage decreases the amperage, keeping the power constant.

    The real key here is that when you transmit power, it goes in all directions away from the transmitter, but the receiving antenna is very small and therefore captures only a small part of the transmitted energy. The rest is lost.
  13. Apr 9, 2009 #12


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    Unless you have highly directional transmitting and receiving antennas, almost all of the energy radiated by the transmitter will be wasted. And highly directional antennas tend to be rather large.

    Consider this UHF TV antenna, which I happen to have on my roof (the lower antenna is for VHF channels 7-13). It's about 2.4 m long. You can see the directionality pattern on the first linked page. Channels 20-60 span a frequency range of about 500-750 MHz. I suppose for higher frequencies you can scale the design in inverse proportion, but someone who knows more about antenna theory than I do (which is very little) can give more details.

    Of course, highly directional antennas have to be aimed carefully. The box just above the roofline in my setup is a remote-controlled rotator.
    Last edited: Apr 9, 2009
  14. Apr 9, 2009 #13


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    For the TV antenna, yes you could scale it to be resonant at higher or lower frequencies. The TV antenna is a log-periodic dipole array. It is based on a design which can theoretically have an infinite bandwidth. In reality, the bandwidth is limited by the size of the antenna. The smaller you can make the antenna's components the higher the frequencies you can reach and the larger you can make it the lower the frequencies. Log-periodic antennas are based upon self-similar principals. Other examples of self-similar antennas are bowtie and planar spiral antennas. Both of these antennas can have infinite bandwidth but again are actually limited by physical constraints.
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