Not built yet. This is my plan and parts list. When it's done I'll add what actually happened.
What to expect
Morse is a skill first and a gadget second. The kit is cheap and quick. The learning takes regular practice.
- Learning takes weeks, not an evening. Ten or fifteen minutes a day works better than one long session. Most people hit a flat patch somewhere in the middle. That's normal.
- The crank set is for practice across a room. A red LED is easy to read a few metres away indoors. It is not a long-distance signal lamp.
- The mirror needs sun. On a clear day a mirror flash can be seen from a long way off. On a grey day it does nothing.
- You need two people for real use. On your own you can practise sending and receiving with a recording or app. Reading someone else's light or mirror is the real test.
Why this way
If you learn "A is dot dash" from a chart, you end up counting dots in your head and translating. That stalls you at a slow speed. Learning each letter as a sound, the way you'd recognise a word, is faster in the end.
A small DC motor works backwards as a generator. Turn the shaft and it makes electricity. That is all you need to light an LED, so the practice set has nothing to go flat.
A straight key is just a sprung switch, but it feels right and it's built to be pressed thousands of times. A push button wears out and teaches a bad hand position.
An LED lights on a few milliamps, so the crank turns easily and you can keep going. A filament bulb would need far more power and make your arm ache.
An LED only lights one way round. Fit a second one the other way and it lights whichever way you crank. It also protects the first LED from being pushed the wrong way.
The sun is the strongest light source you'll ever have. Armies sent Morse with sunlight and mirrors (heliographs) long before radio was common. A mirror is the battery-free way to signal far.
How it works
The code is about timing
Morse is built on one unit of time. A dot is one unit on. A dash is three units on. Inside a letter, the gap between dots and dashes is one unit off. Between letters the gap is three units. Between words it's seven. Get the gaps right and anyone can read you, at any speed.
The crank set
Inside a small DC motor there are magnets and coils of wire. Feed it electricity and it spins. Spin it by hand and it does the opposite: the coils move past the magnets and that pushes a current out of its wires. That's a generator. The faster you turn, the higher the voltage.
The circuit is one loop. Generator, key, resistor, LED, back to the generator. The key is a switch. Press it and the loop is complete, so the LED lights. Let go and the loop is broken, so it goes dark. The resistor limits the current so the LED doesn't burn out if you crank hard.
Why 470 ohms: a red LED needs about 2 V and is happy on 10–20 milliamps. At 6 V, 470 ohms lets through about 8–9 mA, which is clearly visible indoors. If you crank hard enough to reach roughly 12 V, it's still only about 20 mA. So you can't easily overdo it.
What to buy
These are affiliate links. If you buy through them I make a small commission, at no extra cost to you. It helps cover the cost of running this site. This is a hobby, not a shop.
Listings change, so check each one before you order. Budget roughly £40 if you buy everything, less if you already have a resistor and some leads.
Learning
Crank practice set
Daylight signalling
Tools: small flat screwdriver, wire strippers or scissors. A soldering iron is optional.
Build it
Six steps for the crank set. Do it on a table with crocodile clips first. Only make it permanent once it works.
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Find the parts you need
Take out two red LEDs and one 470 ohm resistor. On a 4-band resistor that's yellow, violet, brown. On a 5-band (1%) one it's yellow, violet, black, black, brown. If you're unsure, check it on a multimeter's resistance range.
Why: the wrong resistor is the easiest mistake. Too low and the LEDs burn out, too high and they barely glow.
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Pair the LEDs back to back
Each LED has a long leg (positive) and a short leg (negative). Hold the two side by side so the long leg of one is next to the short leg of the other. Twist each pair of legs together, or join them with clips.
Why: the crank can turn either way, and each way pushes current in the opposite direction. One LED lights for each direction, so it doesn't matter which way you turn. The lit LED also stops the other from being pushed hard the wrong way, which can damage an LED.
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Add the resistor
Clip the resistor to one of the joined pairs of legs. It doesn't matter which side, or which way round the resistor goes.
Why: in a single loop, the same current flows everywhere, so the resistor does its job wherever it sits.
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Wire in the key
The key has two terminals, usually screws. Clip one to the free end of the resistor. Clip the other to one wire from the generator. Clip the generator's second wire to the other LED pair joint. That closes the loop, through the key.
If the key has an adjusting screw for the gap, set it so the contacts are about the thickness of a thin card apart. If it has a spring tension screw, set it so the lever comes back up firmly but isn't hard to press.
Why: a small gap and light spring let you send fast without tiring your wrist. Too wide a gap makes dots sloppy.
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Test it
Turn the crank steadily with one hand. Press the key with the other. One LED should light while the key is down. Turn the crank the other way: the other LED should light instead.
Why: a steady crank gives a steady brightness, so your dots and dashes look the same length to whoever's reading. You may feel the crank get slightly stiffer when you press the key. That's the generator doing work.
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Optional: try a bare motor
Swap the crank for one of the 130 motors. Spinning its shaft with your fingers won't light the LED. It needs to spin thousands of times a minute. Try winding a cord several times round the shaft and pulling it sharply, like starting a spinning top. Or drive the shaft from a large wheel with a rubber band.
Why: this shows why the bought crank has a gearbox. The motor is the same idea; the gears just turn a slow arm into a fast shaft.
Once it works, you can put the LEDs and resistor in a small project box with the LEDs poking through two 5 mm holes. Solder the joints, or keep the clips if you like being able to change things.
Learning + sending
Learn by ear
The method I'm following is the Koch method. In one line: you hear every letter at full speed from day one, start with just two letters, and add one more each time you're getting about 90% right. You never slow the letters down, so you never learn them as counted dots.
Two letters, full speed
Start with two letters, for example K and M. Listen at around 20 words per minute character speed, and write down what you hear.
Why: at that speed each letter is too quick to count, so your brain learns the sound as a whole.
Add one at a time
When you're scoring about 90% over a few minutes, add the next letter. Keep the old ones in the mix.
Space it out if needed
If full speed is too much, keep the letters fast but leave longer gaps between them. That's called Farnsworth spacing. Close the gaps up as you improve.
Little and often
Ten to fifteen minutes a day. Stop while you're still sharp.
Why: this is a recognition skill, like learning a language by ear. It builds with regular short sessions far more than with long ones.
You'll need something that plays Morse at you. The free site LCWO (Learn CW Online) runs a Koch course in the browser. Use any phone or computer for that, then put it away and practise sending on the crank set.
Quick reference
For checking, not for learning from.
| Letter | Code | Letter | Code | Letter | Code |
|---|---|---|---|---|---|
| A | · – | J | · – – – | S | · · · |
| B | – · · · | K | – · – | T | – |
| C | – · – · | L | · – · · | U | · · – |
| D | – · · | M | – – | V | · · · – |
| E | · | N | – · | W | · – – |
| F | · · – · | O | – – – | X | – · · – |
| G | – – · | P | · – – · | Y | – · – – |
| H | · · · · | Q | – – · – | Z | – – · · |
| I | · · | R | · – · | 0–9 | see below |
Numbers are always five symbols. 1 is · – – – –, 2 is · · – – – and so on, swapping one dash for a dot each time, up to 5 (· · · · ·). Then 6 is – · · · ·, 7 is – – · · ·, through to 0 (– – – – –).
Sending with the mirror
Aim with your fingers
Stand with the sun in front of you or to one side. Hold the mirror near your eye. Stretch out your other arm and make a V with two fingers around the person you're signalling. Tilt the mirror until its patch of light lands on your fingers.
Why: you can't see the beam in the air, but you can see it on your hand. If it's on your fingers and the target is between them, it's on the target.
Flash by tilting
Tilt the mirror slightly off and back on to make each dot and dash. Send slowly, much slower than by ear, with clear gaps.
Why: at a distance a flash is easy to miss, and the person reading needs time to be sure it was a dash and not a dot.
Agree a start signal
Before you start, agree a sign that means "ready" and "repeat that", for example a long steady flash. It saves a lot of confusion.
With no light at all, sound works too. A whistle, or tapping on a pipe or table, carries Morse the same way: long and short, with the same gaps.
If it's not working
| What you see | Likely cause | Fix |
|---|---|---|
| No light at all | Loop broken somewhere | Check every clip. Then clip the generator straight to the resistor and LEDs, leaving the key out, and crank. If that works, the key isn't closing. |
| Lights one way only | Second LED in the same way round, or dead | Turn the second LED round so long leg meets short leg. Try a spare. |
| Very dim | Cranking too slowly, or resistor too big | Crank faster and steadier. Check the resistor is 470 ohms, not 4.7k. |
| LED flashed bright then died | No resistor in the loop | Fit the 470 ohm resistor and use a new LED. |
| Light flickers with each turn | Uneven cranking | Keep a steady rhythm. A bit of flicker is normal at low speed. |
| Stuck on the same letters for days | Normal plateau | Keep the daily sessions short. Drop the speed of the gaps, not the letters. |
Safety
- Never flash a mirror at drivers, pilots or anyone's face. A mirror flash can dazzle. Only signal someone who knows it's coming and is not driving.
- Don't look at the sun while aiming. Look at your fingers and the target.
- Distress signals mean distress. SOS (
· · · – – – · · ·) brings real help. Don't send it in practice where anyone could see it. - The crank set runs on a few volts. There's nothing dangerous in it.
Notes
The Koch method is named after Ludwig Koch, a German psychologist who studied how people learn Morse in the 1930s. Farnsworth spacing is named after Donald Farnsworth, a radio amateur who popularised it. The free LCWO site builds both into its lessons.
The LED and resistor figures are standard values for ordinary 5 mm red LEDs. The crank set hasn't been built yet. I'll add what it's actually like to use when it is.
Related guides: battery-free shortwave radio (where you'll hear Morse as thumps), sound-powered phones, wind-up torches and radios.