Convert low frequency radio waves into small amout of electricity

Projects General Guidance
1

Sooo...

I've seen about 5~6 years ago that kind of circuit made by a man that can take the radio waves
and transform them in a small amount of electricity that can run at least a led or a small chip, does
anyone know anything about that? It came in my mind few minutes ago so I'd like to share my idea/past
information and see if that kind of circuit it's possible to be made to power up something small.

As few of people know in this forum low freq we get from old TV stations (we mostly use nowadays satellite or IP TV) and mostly common Radio station at 70~100+Mhz, lower the freq bigger range
but what about power and usability in this project?!

My idea is to create a receiver but as we know receiver need battery to work and power up speaker
and necessary components, I'm not a big Pro in Radio electronics but i know the basic stuffs how a
radio circuit works because of the past mini bug tx/rx circuits :smiley:

So any Pro Radio member who can explain how that can be possible to be done?
Anyone can participate and tell their opinion, just don't spam. :slight_smile:

Thanks,
Domino60

2

You can get voltage from radio waves crystal radio does that. So you could get something but how much would depend on where you are at.

3

RFID does this. A small identity chip in your dog or price tag can be powered by a transmitter within a few feet. Powering an LED this way is not practical as the amount of power for an LED is thousands of times more.

There are wireless charging pads for phones that can transmit a useful amount of power but the transmission distance must be around 1mm. So not useful for most other purposes.

Induction cooktops use radio frequency to heat your saucepan without wires but that only heats - lighting an LED is still difficult.

Nikola Tesla invented a system to transmit power worldwide but it failed, mainly because there was no way to bill people for the power they used.

4

I made a similar system in the 60s. A medium wave crystal set with a one transistor amplifier powered parasitically from a long wave commercial radio station. I used a 50 ft long wire antenna and there was precious little signal. Which is the problem, unless you have a nearbye transmitter hen it is a non starter.
The circuit is simply a tuned LC circuit a full wave rectifier using germanium diodes and a capacitor.

5

There are great collections of beautifully made "self powered" crystal radio sets here and here.

6

To get any kind of usable power you need to live close to an high power AM broadcasting station, within a few kms.
Then the circuit for a small crystal set will make enough power to light a very small led.

7

The reason that this is very difficult is that an antenna for most RF sources is likely omnidirectional, so only a very small fraction of its power arrives in your direction. Furthermore, signal strength drops off as the square of distance, so the double whammy here is that even if you start with a kilowatt 1 miles away, the power is very low. By way of example, a 10 mw. transmitter may provide about 0.000000001 mw at a distance of 300 ft., reference to a "typical" receive antenna.

So if we scale this to a 1 KW transmitter a mile away, we get about 0.000000032 mw power at our antenna. Only with a very massive receive antenna could you hope to drive this up to a level which could light an LED.

8

Google "Freevolt".

9

"Magnet motors" may be another useful thing to Google if you need something to pass the time.

...R

10

Bessler wheels are by far the best.

11

RFID does this. A small identity chip in your dog or price tag can be powered by a transmitter within a few feet. Powering an LED this way is not practical as the amount of power for an LED is thousands of times more.

There are wireless charging pads for phones that can transmit a useful amount of power but the transmission distance must be around 1mm. So not useful for most other purposes.

Those are mostly known "AC coil" getting close a active AC coil and a non active, the non active will start
move the electrons indite because of the field inside the active coil, it's not a Radio wave(freq) but a magletical movement, of curse if we go really deep about that 2 we got many things in common .

I made a similar system in the 60s. A medium wave crystal set with a one transistor amplifier powered parasitically from a long wave commercial radio station. I used a 50 ft long wire antenna and there was precious little signal. Which is the problem, unless you have a nearbye transmitter hen it is a non starter.

In my country we got in every corner Radio telecomunication antennas (mobile network, GMS, GPRS, EDGE, HSPA, HSDPA, UMTS..etc) which they all work from 850Mhz to 2.1Ghz+ and there is also TV and Radio FM/AM waves. So I got here a lot of Radio Freq waves which I could use them :smiley:

There are great collections of beautifully made "self powered" crystal radio sets here and here.

Saw some examples and few of them need battery power, we are talking about a small device which could get Radio Waves and turn them into electricity.

The reason that this is very difficult is that an antenna for most RF sources is likely omnidirectional, so only a very small fraction of its power arrives in your direction. Furthermore, signal strength drops off as the square of distance, so the double whammy here is that even if you start with a kilowatt 1 miles away, the power is very low. By way of example, a 10 mw. transmitter may provide about 0.000000001 mw at a distance of 300 ft., reference to a "typical" receive antenna.

The closest telecomunication antenna from my house is 200m.

"Magnet motors" may be another useful thing to Google if you need something to pass the time.

O_o wut? I spend 2 days of my summer time looking everything about any kind of motor :smiley:

Bessler wheels are by far the best.

It was made to do heavy work for long periods, and in an official test it ran continuously for 54 days.
Looks like it was a mechanism like the mechanic watch, why? because ran only for 54days, after that
he should of somehow start it again.

12

mauried:
Bessler wheels are by far the best.
http://www.besslerwheel.com/

We obey the second law of thermodynamics on this forum thank you my good man. >:(

13

Domino60:
why? because ran only for 54days,

He wasn't using unsigned longs :slight_smile:

...R

14

Most likley was the worlds very first free energy scammer though.
Thats got to be worth something.

15

Those are mostly known "AC coil" getting close a active AC coil and a non active, the non active will start
move the electrons indite because of the field inside the active coil, it's not a Radio wave(freq) but a magletical movement, of curse if we go really deep about that 2 we got many things in common .

I think there are some things you are not understanding. Radio waves are electromagnetic radiation. A coil fed with an ac current will produce electromagnetic radiation just as a dipole antenna fed with alternating voltage will produce electromagnetic radiation. They are just complimentary types of antenna.

The closest telecomunication antenna from my house is 200m.

Take as an example a mobile phone mast giving say, 100 W of radiation. At 200 m, assuming an isotropic antenna, you would get 0.2 mW of power in each effective square metre of antenna. If you assume about 6 dB of transmitter antenna gain you would still only be receiving just under 1 mW, hardly enough to do anything useful.

Why bother when sunlight ( which is effectively high frequency radio waves) is giving you several hundred Watts per square metre?

Russell.

16

I think there are some things you are not understanding. Radio waves are electromagnetic radiation. A coil fed with an ac current will produce electromagnetic radiation just as a dipole antenna fed with alternating voltage will produce electromagnetic radiation. They are just complimentary types of antenna.

Yes I understand that's why I said they have many things in common but work differently.

Take as an example a mobile phone mast giving say, 100 W of radiation. At 200 m, assuming an isotropic antenna, you would get 0.2 mW of power in each effective square metre of antenna. If you assume about 6 dB of transmitter antenna gain you would still only be receiving just under 1 mW, hardly enough to do anything useful.

Why bother when sunlight ( which is effectively high frequency radio waves) is giving you several hundred Watts per square metre?

I'm not an expert in Radio/telecomunication but looks a nice project to do but only for fun/education,
to get some free energy better use some solar panels and power up a circuit easy + add a coin battery to be powered up night.