RTTY dates to mechanical teleprinters and still uses the five-bit Baudot code they used, which is why it has no lower case. Two tones shifted 170 Hz apart represent mark and space.
It is not sensitive by modern standards, but it is fast, well established and utterly dominant in certain contests. The distinctive warbling sound is one of the signatures of the HF bands.
At a Glance
- Category
- Digital data
- Bandwidth
- About 250 Hz
- Speed
- 45.45 baud, roughly 60 words per minute
- What you need
- A sound card interface. Historically a hardware terminal unit
- Where to listen
- RTTY segments of the HF bands, extremely busy during RTTY contests