‘Gibson Girl’ Emergency Beacon Built From A Wind-Up Flashlight

Batteries flat and no cellphone coverage and you need to communicate hundreds of miles?  No problem. [Peter Parker VK3YE] has created a wind-up ham radio transmitter built into a discount store crank-handle flashlight (or torch). No batteries – all power comes from you turning the hand crank. This design was inspired by the ‘Gibson Girl’ emergency beacon transmitter used during Second World War. But what used to be an very large, full body cranking box is now tiny and simple to crank. Let’s take a look at he video and the build details after the break.

With a simple wire antenna its continuous wave (CW) morse code signals can be heard hundreds of kilometers away, which is demonstrated in the video.

How it’s built

gibson-girl-internalsRemoving the torch’s LEDs, battery and PC board frees room for the three transistor transmitter. The generator remains to power the transmitter.

The first transistor is an RF oscillator using a 7.023 MHz crystal. It’s on whenever the handle is being cranked. The oscillator’s output is amplified by the second transistor connected as an RF power amplifier. Its output goes to the antenna via a low pass filter which suppresses harmonics. The faster you crank the greater the RF output but 500 milliwatts is typical.

Sending Morse code requires that the transmitted signal be switched on and off. This is accomplished by the keying transistor which energizes the RF power amplifier only when the key is pressed. This simple and reliable transmitter circuit is based on the famous OXO by [George Burt GM3OXX] many years ago.

A momentary push-button switch salvaged from an old video recorder acts as the key. Mount this in a spot where you can press it with the hand holding the torch while cranking the generator with the other.

Construction cost is under $20 and the project can be built in a day. The video linked above includes a description, a demonstration and circuit diagram. The one below shows a demo of [Peter’s] hand-cranked radio communicating with a station 700km away. We think some possible add-ons for the ingenious device include a companion receiver, a PIC-controlled automatic keyer or a GPS attachment that send the position in Morse.

21 thoughts on “‘Gibson Girl’ Emergency Beacon Built From A Wind-Up Flashlight

    1. But this will probably work just as well in 6 years’ time. Your alkaline batteries have a good chance of popping.

      I would love to see a unit with GPS and enough logic to transmit “SOS AussieLauren at 67° 36′ 10″ S, 62° 52′ 26″ E has activated their personal safety beacon” on APRS or the appropriate message on the 406MHz EPIRB satellite-tracking

        1. Well I just put some Duracell batteries in my newly bought Steamlight Stylus Pro flashlight. I accidentally left it on and when I went to replace the batteries, they had leaked inside the flashlight. The expiration date on the Duracells was 2018.

          Fortunately Streamlight sent me a new tails witch for free.

          Ultimately, I’ve had batteries I thought were good go bad before I’ve used them, and I have left stuff on by accident or bumped the switch and drained good batteries.

          What exactly is the point of making your comment?

          1. I love the comments thinking the hand crank is useless.
            Batteries have flaws, and yea, so does a hand crank.
            I would much rather have a hand crank than a set of batteries if I was heading out. Especially if I go for a dip in the water. If you have batteries in your device you could have killed it. Assuming you can dry it out, the hand crank will still work.

          2. The point is that you can break anything if you’re stupid enough, but good batteries are still smaller and lighter than a crank mechanism, and just as reliable with a bit of Care deeply

          3. Exactly, the nice thing about the hand crank model is that once built none of the components are likely to go out except with excessive use. Since it’s intended purpose is as an emergency beacon, it won’t be getting a lot of use and can just be kept on hand without having to remember to bring extra batteries. It’s just there, it just works, perfect emergency device.

      1. Have a look at molten electrolyte batteries (armies like to use them in man-portable guided missiles, both anti-tank and anti-aircraft), those can easily do 30 years in storage and yet they can crank a fair bit of power (90-ish watts for something the size of a hand grenade) once activated…however once that’s done they won’t last very long…

    2. The average soldier fields 17 pounds of battery for all the gear used in today’s mobile army.
      They are working on a shoe that squeezes out juice to recharge/replace some of that load.
      The plastic gears inside one of those lights are a goner in dirty/sandy use.

      1. Problem is that decent human charging requires extra food and causes extra fatigue. Probably not a good trade off for a soldier. And a shoe that doesn’t cause any discomfort/inefficiency in walking probably doesn’t have that much power.

  1. Interesting!

    His idea brings to mind an incredible account of a young man who drifted across the Atlantic in a life raft.


    He had an EPIRB that he triggered when his lifeboat sank, but its batteries only lasted 24 hours and weren’t heard. In the book, he concluded that he’d have been better off if he had a marine VHF radio. Several times, he came within sight of a freighter or tanker, but given how small his vessel was and how little attention those on the bridge were paying, he wasn’t seen. Even his flares, when he had them, weren’t noticed.

    Ships do, however, monitor marine VHF channel 16. If he’d had a handheld radio, he’d have been able to summon help.

    Peter might want to see design two variations using this same crank flashlight:

    1. 12 volt output for marine VHF and ham VHF radios.

    2. 5 volt output for cell phones.

    A DC-to-DC converter and some filtering and regulation would be helpful.

    1. Resistance to prolonged sea water exposure is not a small thing, esp. for devices with electronics, gears, etc. The seal for the hand crank is a major engineering challenge all in itself.

    1. This, much likey.

      Also, the horizontal axis design is far superior to a vertical one. Arms are better at applying force vertically than horizontally. Those “Gibson Girl” cranks look like a slipped disk waiting to happen. If you made a commercial offering like this I’d make the crank longer and add something like a rifle’s butt to give you something to pull against. Though, It’d be a lot bigger then…

  2. So does 0:31 to 0:34 in the video remind anyone of their early teenage years? Anybody? I agree that supercaps would be a good addition, and maybe a solar cell for when it’s sunny out, same yourself some work.

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