Numbers Station Generator
Type a message. Get a coded shortwave transmission your audience can actually decode, with the interval signal, call-up and band noise of the real thing.
What a numbers station is
Numbers stations are shortwave broadcasts that send nothing but strings of figures, usually read in a flat voice or keyed in Morse. They ran through the Cold War and some are still on the air. A station typically opens with an interval signal, repeats an identifier, announces how many groups are coming, sends the groups twice, and closes.
The format exists because it is simple and cannot be traced to a receiver. Anyone can listen. Only the holder of the matching key can read it.
How this tool encodes your message
Each character becomes two figures. Those figures are then split into groups. The substitution is published below, so anyone with this page can reverse it. Treat it as a prop, a puzzle or a teaching aid, not as security.
If you paste text that is only digits and spaces, the tool uses your figures exactly as typed. That lets you bring your own cipher and keep it to yourself.
| Character | Figures | Character | Figures |
|---|---|---|---|
| A | 01 | N | 14 |
| B | 02 | O | 15 |
| C | 03 | P | 16 |
| D | 04 | Q | 17 |
| E | 05 | R | 18 |
| F | 06 | S | 19 |
| G | 07 | T | 20 |
| H | 08 | U | 21 |
| I | 09 | V | 22 |
| J | 10 | W | 23 |
| K | 11 | X | 24 |
| L | 12 | Y | 25 |
| M | 13 | Z | 26 |
| space | 00 | digits 0-9 | 30-39 |
| . | 27 | , | 28 |
| ? | 29 |
The parts of the transmission
- Interval signal
- A repeating three-note motif before the message. On a real station it marks the frequency as occupied and lets a listener tune in before the traffic starts.
- Call-up
- The station identifier sent three times. Many stations were known only by this number.
- Group count
- How many groups follow, sent twice, so a listener knows whether they missed any.
- Message
- The figure groups. Sending them more than once is normal, because shortwave fades.
- End marker
- The Morse prosign AR, meaning end of message.
Using it in a production
- Make it decodable. Players and viewers who try to decode a prop and find it is gibberish feel cheated. A real encoding rewards them.
- Slow the keying down. At 10 to 12 WPM an audience can write the figures down from the audio.
- Keep the noise up. Band noise around 60 to 80 percent reads as authentic without burying the signal.
- Use one repeat for a short scene, two or three when the transmission plays under dialogue.
Questions
Why can spoken mode not be downloaded?
Browser speech synthesis is produced outside the page audio graph, so a web page cannot record it. Morse mode renders entirely inside the page and downloads exactly as you hear it.
Is this legal to make?
Yes. You are generating an audio file, not transmitting. Broadcasting on shortwave without a licence is a different matter and is not something this tool does.
Can I decode a real recording with this?
No. This generates transmissions, it does not receive them.