Getting power from radio waves

[lmcelhiney]

Truth: Free Power Radio

Since others, like me could find this thread via Google and with the full realization that it is "very" old, I just wanted to bring some facts into the discussion.

Actually, the "free power radio" goes beyond a crystal set. You can actually power a single transistor radio circuit using this concept.

The key is that you use two tuned circuits and live in an area with one or more strong local transmitters.

The first circuit is like a crystal set and it is tuned to the "loudest" local station. The RF signal from that is detected to provide voltage to the second tuned circuit.
(Voltage multiplication techniques could be used to raise the absolute potential)

The second tuned circuit RF is detected and is the input to the transistor stage. The voltage for the amplifier comes from the first tuned circuit.

The second, adjustable, tuned circuit will then function as a receiver with a single stage of audio amplification.

Low power devices are obviously the best for this design. Germanium devices with their 0.2V drop would be best if they are available.

 

[Externet]

If you are nearby a radio station, or power transmission lines, start tinkering with:

LTC3108; LTC3588-1

I believe you do not need a resonant circuit tuned to a single broadcast station nor to 60 Hz to harvest something. A plain long wire with a diode at its end should rectify all waves hiting the wire at all frequencies.
I would like opinions from knowledgeable members on that please.

 

[Behemoth]

So, I threw a bunch of scrap wire and aluminum flashing in my attic. I hooked a wire to it with a white LED at the end. I then wired the led to a large grounding rod. LED lit up. Open circuit voltage without the diode was 17 VAC. I live in town so AC waves and transformers are everywhere. I just don't know if this is stealing from the electric company or was it wasted energy anyway. Might not seem like much...but the solar array doesn't pick up much at night and I would like a trickle charge on the batteries at night...even a .001 amp at 13-17 volts will provide me with a net gain preventing the batteries from discharging into silly things like high humidity. Yes I know, old thread. Sorry.

 

[cowboybob]

Welcome to ETO, Behemoth!

Yeah, old thread, but your addition is fine.

No laws broken broken that I know of and I'm not surprised you are able to harvest some juice (mostly domestic AC). Linear Technology has some very effective SMPS devices for just that purpose: https://www.linear.com/products/step-up_(boost)_regulators.

 

[Behemoth]

Thanks Bob!

I'm just beginning to learn the depths of RF and AC so...I'm guessing building a resonate circuit that operated at 60hz might be illegal...but a large energy collector is fine. I don't really understand resonance on an intimate level, but I guess that it would sap power directly? Just curious. Definitely considering a boosting circuit, I wish there was a non-emp emitting oscillator that didn't rely on silicon. I have a bad tendency to fry expensive components.

 

[Tony Stewart]

Ok, so you all say its impossible to power a LED in this way?

It is very possible and easy to do if you have a large diameter RF coil to send power and similar to receive power. Using step-up tapped coil to send and step-down tapped coil to receive the coil coupling must be less than or equal to the diameter for reasonable power coupling, then limited only by the transmit power level. Using 1:50 then 50:1 turns ratio or more boosts the EM field in between since an LED ESR drops to 15 Ohms which would attenuate greatly impedance ratio from any coil antenna.

You can make an LED glow dim with a long wires that picks up line E fields and then even just connected to one side. Ensure you have reverse polarity protection or run back to back in parallel. But don't expect 60mW of power per 5mm LED unless you have good coupling. try a back to back pair with an antenna near a microwave oven seal for leakage.

 

[tcmtech]

Harvesting lost ambient energy is not a crime that anyone is going to go hunting you down for any more than they will for you stealing a whiff of the smell of your neighbors flowers when the wind is right.

Maybe if you manage to come up with a way to draw a few kilowatts or more continuously from someone else's supply systems but not a few tens of milliwatts.

BTW with a tuned resonant circuit the odds are you will be stealing lost power from your own home electrical systems anyway unless you live right under some large utility lines.

 

[Behemoth]

There is a transformer 20 yds behind my house. Kinda figured it would draw from my lines too...also not going to try to steal anything. I did learn a lot about resonant frequency today though. Thanks guys.

 

[Willen]

An electronics proffesional has told me that i can get a couple of volts with that stuff.

Are you shure it cant power a LED?

Yes, you can! I am a proof! Here's my full story about it-
My house has a metal as a roof and it's almost 12x12 meters wide. All pieces of metals (roofs) are connected electrically. So I got 12x12 wide 'antenna' for radio waves. The roof is not grounded because my house has been made by wood (not by cement and rods).

First I made a simple crystal radio- A coil, germanium diode and a earpiece, I could hear pretty audiable voices of stations of my own country Nepal; also received from China, India etc during night. Later I had to add 1nF cap across coil to eliminate stations overload.
(I earthed one meter aluminium plate for earth connection a poured water there for wet/nice earthen).
Once, my body was earthed, and I touched to roof by tongue tip (I do not remember why I did so), and found that the metal was little sour everywhere in taste! Then I found that it's a radio shock, wow! Then I connected a high bright red LED, scrapped from an optical mouse then got a dim light. It was very interesting! Also connected a white medium power LED (1/2 watt maybe), also got very dim light! I measured AC volts from roof to earth and got 11V AC during open circuit, on my poor DMM.

It would be totally free (no bill for electricity) 'indicator' of RF existance on roof! I could connect a LED permanently there, but afraid to killing 'lightning' around summer.

 

[audioguru]

Hi Willen,
If you rectify the AC radio signals with a high frequency rectifier bridge (1N4148 or 1N34A diodes) and use the resulting DC to charge a capacitor then it will power a flashing LED and the light will be much brighter than lighting an LED from AC continuously.
I wonder if your isolated roof picks up a DC positive static charge when the wind blows and removes some electrons.

 

[Tony Stewart]

Power for a dim LED @ 1 mA is only a few mW. Maximum power for one 5 mm LED is ~ 65 mW.
To optimize power transfer RF impedances need to be matched between high free space RF and 15-50 Ohm ESR for thus range.

electrostatic negative voltages below -5V are not permitted.
Considering relative energy avail. of solar , RF capture seems a novelty.

 

[Externet]

Not radio, but what is the total leakage harvested here ?
----> https://www.richardbox.com/field.htm

How would you store that energy in a battery ? Just an antenna to a diode into battery and ground rod to the other battery terminal ? Perhaps Willen's metal roof as antenna ?

Antenna-----------------------------------------|>|-------(+)BAT(-)---------GND

Is it truly placing a load to the transmission line compared to have nothing there ? I see no need for the circuit to be tuned. Any and all signals at any frequency get rectified.

Am not interested in legalese...

 

[Behemoth]

The resulting voltage drop would have to be above that of the battery. But that set-up would work I think. The voltage drop of the diode would be the maximum charge rate of a battery with the same resistance? No. I don't know how to calculate that.

It is a novelty Tony Stewart. Until you have a need to transfer energy without the use of wires. Wires are very expensive if you need a whole bunch. I can think of many ways this information could be useful and profitable.

 

[JimB]

For those who think that there is boundless energy to be harvested from radio signals, have a look at this thread from a couple of years ago where I did some measurements of the voltage developed on a ten metre long antenna.

https://www.electro-tech-online.com...re-from-a-simple-antenna.130178/#post-1080351

JimB