Radioteletype
From Wikipedia, the free encyclopedia
Radioteletype (RTTY) is a telecommunications system consisting of two teleprinters linked by a radio link.
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[edit] How it works
RTTY uses a variety of different modulation methods, of which frequency shift keying is the most common.
- Coding used is typically 5-bit ITA2 code (also known as the Baudot code), which is used asynchronously with start and stop bits.
- At least one common RTTY system uses 6-bit ITA2 character codes.
- More modern systems use 7-bit or 8-bit bytes.
[edit] Slow by modern standards
RTTY is extremely slow by modern standards; a typical baud rate for RTTY operation was 45 baud (approximately 60 words per minute).
The combination of low baud rate with robust FSK modulation makes RTTY highly resistant to most forms of radio interference, second only to Morse code. Part of this is due to the fact that FSK, like FM, always operates at maximum power. FSK is the single most demanding mode for transmitter equipment.
[edit] Spectrum efficiency
RTTY and Packet spectrum efficiency compared with respect to {bits/second} thruput
[edit] Primary users
Principally users that need robust shortwave communications
- Various navies of the world
- Various armies of the world
- Diplomats, especially in Africa and parts of Asia
- Weather reports are transmitted by the US Coast Guard nearly continuously
- RTTY systems are also fielded by amateur radio operators, and are popular for long-distance contacts
[edit] Pronunciation
The pronunciation of RTTY is disputed
- In very few applications, notably the U.S. military, radio teletype is known by the acronym RATT rather than RTTY.
- Those who are actively engaged in amateur RTTY communications pronounce RTTY not by its initials but as "ritty".
[edit] Spectrum usage
Comparisons of MT63, RTTY and HF Packet spectrum
[edit] Media
- A sample RTTY transmission (file info) — play in browser (beta)
- The text "Welcome to Wikipedia, the free encyclopedia that anyone can edit." sent as RTTY.
- Problems listening to the file? See media help.
[edit] See also
- Sailmail, a commercial HF mail system
- SITOR, an RTTY variant with error control.
- PACTOR, a packet SITOR variant
- Hellschreiber, a FAX-RTTY hybrid
- ACARS, used by commercial aviation – packet based
- Navtex, used by maritime navigation
- MT63, used by Hams and some government agencies
- PSK31 & PSK63
- MFSK
- Multiple frequency-shift keying COQUELET and PICCOLO, also referred to generically as Polytone
- CLOVER2000
- Q15X25, a HAM created packet format
