Converting Radio waves into D.C Electrical energy (rf to dc)

Thread Starter

afm707

Joined Oct 24, 2016
20
Can you please help me in guiding how to Convert Radio waves into D.C electrical energy of 1.5 volt
 

ian field

Joined Oct 27, 2012
6,543
Can you please help me in guiding how to Convert Radio waves into D.C electrical energy of 1.5 volt
Could be worth seeking out a few "tricks of the trade" - from the very early days; push-pull crystal sets were popular with American enthusiasts. 2 diodes and, I think 2 tuned circuits. You should also aim for all the bandwidth you can get. Years ago I won a scrap VHF communal TV amplifier, under the chassis was a spiders web of air cored coils strung between standoff posts. Each one was a different length and amounted to a whole bunch of different tuned circuits strung in series. This was done so the amplifier was more or less flat over bands I to III - they probably didn't bother to reject band II.

The theoretical ideal has it that an LC tuned circuit is a short to any frequency either side, but losses make the real world not so much. In essence; if you have a bunch of different LC circuits in series - the off frequency ones will present minimal losses, any LC circuits that are getting something, all add together.
 

Thread Starter

afm707

Joined Oct 24, 2016
20
Could be worth seeking out a few "tricks of the trade" - from the very early days; push-pull crystal sets were popular with American enthusiasts. 2 diodes and, I think 2 tuned circuits. You should also aim for all the bandwidth you can get. Years ago I won a scrap VHF communal TV amplifier, under the chassis was a spiders web of air cored coils strung between standoff posts. Each one was a different length and amounted to a whole bunch of different tuned circuits strung in series. This was done so the amplifier was more or less flat over bands I to III - they probably didn't bother to reject band II.

The theoretical ideal has it that an LC tuned circuit is a short to any frequency either side, but losses make the real world not so much. In essence; if you have a bunch of different LC circuits in series - the off frequency ones will present minimal losses, any LC circuits that are getting something, all add together.

can you give me more information please
Thanks
 

tcmtech

Joined Nov 4, 2013
2,808
It depends on what frequency or range of frequencies you want to tap into to get power from and how much power as well.

The simplest is little more than a a tuned LC tank circuit set to the frequency you want to tap into that uses one or more crystal diodes to convert the high frequency RF signal to simple DC.

There's a pile of YouTube videos on the subject with a number of them showing how people light up LED's ans what not by pulling power off their local radio, television station and other such high powered RF source carrier signals
 

ian field

Joined Oct 27, 2012
6,543
It depends on what frequency or range of frequencies you want to tap into to get power from and how much power as well.

The simplest is little more than a a tuned LC tank circuit set to the frequency you want to tap into that uses one or more crystal diodes to convert the high frequency RF signal to simple DC.

There's a pile of YouTube videos on the subject with a number of them showing how people light up LED's ans what not by pulling power off their local radio, television station and other such high powered RF source carrier signals
I've hard of people in the immediate vicinity of a transmitter harvesting enough energy to light their houses.

With modern LED lighting - the vicinity might not have to be quite so immediate.
 

Thread Starter

afm707

Joined Oct 24, 2016
20
It depends on what frequency or range of frequencies you want to tap into to get power from and how much power as well.

The simplest is little more than a a tuned LC tank circuit set to the frequency you want to tap into that uses one or more crystal diodes to convert the high frequency RF signal to simple DC.

There's a pile of YouTube videos on the subject with a number of them showing how people light up LED's ans what not by pulling power off their local radio, television station and other such high powered RF source carrier signals
i don't need free energy
just "Wireless Power Transmission"
 

Externet

Joined Nov 29, 2005
1,403
... a tuned LC tank circuit set to the frequency you want to tap into that uses one or more crystal diodes to convert the high frequency RF signal to simple DC...
Hello tcmtech... Can you elaborate that; I have before seen that comment and do not understand why tuning to a frequency instead of harvesting all the frequencies on the air ?
Example... barbed wire(s) fence on a farm... proper diode rectification hooked to it... a good ground... should pick up everything, from the nearby power transmission line to the faint broadcasted RF... or not ?

A tuned circuit would yield a higher current or voltage if parallel or series LC, but only at that frequency. The rest of RF is ignored, 'wasted' from harvesting ¿?

And then, there will be rectennas some day...
http://www.intechopen.com/source/html/45904/media/image42_w.jpg
 
Last edited:

ian field

Joined Oct 27, 2012
6,543
Use an IC and its circuit to get your 1.5V. Several options here, you should choose the most convenient for your case :

----> https://duckduckgo.com/?q=energy+harvesting+ic&t=canonical&ia=web

Drool here :

---->
When I was a kid, a bunch of us raided the local tip - we found a skip of 8' fluorescent tubes.

When we tired of the jousting tournament on our bicycles, we took as many tubes as we could be bothered fetching and planted them in a nearby ploughed field under the 400kV overhead lines. The railway line ran close by, so the evening commuters were treated to a forest of eerie glows.
 

Externet

Joined Nov 29, 2005
1,403
Nice !
The energy that lights up those fluorescent tubes, is radiated by the high tension line above... one end of the tube grounded, the other as a tiny harvesting antenna.
If there were no fluorescent tubes planted, the radiated energy would just hit ground; is that correct ?

So having the tubes planted there does not consume additional energy from the power station, that otherwise is normally lost, right ?
I asked a friend that used to install 13KV rural lines to attach fluorescent tubes with nylon ties to the high tension wire. Has not done it yet, but would them light up that way ?

__________________________________________________________
=============================

__________________________________ = HV transmission line

============= = fluorescent tube
 

BR-549

Joined Sep 22, 2013
4,936
I don't think the TS is trying to harvest energy. I believe he wants to charge or energize wirelessly.
 

hp1729

Joined Nov 23, 2015
2,304
It depends on what frequency or range of frequencies you want to tap into to get power from and how much power as well.

The simplest is little more than a a tuned LC tank circuit set to the frequency you want to tap into that uses one or more crystal diodes to convert the high frequency RF signal to simple DC.

There's a pile of YouTube videos on the subject with a number of them showing how people light up LED's ans what not by pulling power off their local radio, television station and other such high powered RF source carrier signals
Why any specific frequency? Why not any and all the antenna will pick up?
 

ian field

Joined Oct 27, 2012
6,543
Why any specific frequency? Why not any and all the antenna will pick up?
In accepted terminology - a high Q LC circuit is said to have "gain", but only at a specific frequency. You can detune it to get a wide bandwidth by shunting it with a "Q spoiler" resistor - but that clearly isn't what the TS wants.

The solution is what I said quite a few posts back - series connect multiple LC tank circuits.

Just an antenna will get you a few tens of uV - if you're lucky, and then it takes careful design to get any current whatsoever.

The antenna also has to be resonant at a frequency where some energy is - but the efficiency is so low, its pretty much a secondary concern.
 

hp1729

Joined Nov 23, 2015
2,304
In accepted terminology - a high Q LC circuit is said to have "gain", but only at a specific frequency. You can detune it to get a wide bandwidth by shunting it with a "Q spoiler" resistor - but that clearly isn't what the TS wants.

The solution is what I said quite a few posts back - series connect multiple LC tank circuits.

Just an antenna will get you a few tens of uV - if you're lucky, and then it takes careful design to get any current whatsoever.

The antenna also has to be resonant at a frequency where some energy is - but the efficiency is so low, its pretty much a secondary concern.
So if the objective is to capture as much energy as possible an antenna with as broad a range as possible would be better? Like a TV antenna with multiple elements of different sizes covering VHF to UHF? Or would the voltages tend to cancel each other out?
 
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