As a long-time amateur radio operator, I've always had a soft spot for RTTY (Radio Teletype). One of its most recognisable features is the characteristic sound it makes on the air - the famous RTTY "diddles".
These diddles are a rapid alternation between the mark and space frequencies, creating a distinctive "dee-dah-dee-dah" sound. It's a bit like a fast, repetitive Morse code "di-dah", hence the nickname. This sound occurs when the transmitting station is idle, waiting for the next character to be sent.
The diddles serve a practical purpose beyond their unique audio signature. They help receiving stations to maintain synchronisation and tune their equipment properly. For DXers like myself, hearing those diddles through the noise can set the heart racing - it often means a potential rare contact is calling.
RTTY's origins date back to the 1920s and 1930s when it was developed for commercial and military use. Amateur radio operators began experimenting with it in the late 1940s and early 1950s. The mode uses frequency-shift keying (FSK), typically with a 170 Hz shift between mark and space, and the Baudot code for character encoding.
In the early days, RTTY required substantial hardware - massive mechanical teleprinters (like the Model 28 shown here) that were noisy and maintenance-intensive. The transition to computer-based systems in the 1980s and 1990s made RTTY more accessible, though some might say the loss of the physical teleprinter's clatter removed some of its charm.
Despite the proliferation of newer digital modes, RTTY has maintained its popularity. It's still widely used in contests and for general QSOs. Major events like the ARRL RTTY Roundup and CQ WW RTTY contests keep the mode very much alive.
What I appreciate about RTTY is its robustness. It might not be as efficient as some newer modes, but it performs well in poor conditions. There's something deeply satisfying about seeing that text slowly appear on the screen, accompanied by those iconic diddles, especially when it's from a DX station.
Today, with modern software (such as MMTTY, shown here above) and interfaces, getting on RTTY is easier than ever. While it may not be the most advanced digital mode, its historical significance, continued use, and those unmistakable diddles make it a crucial and beloved part of our hobby.
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