RTTY

Raffaello Tesi

RTTY, that is, “Radioteletype”, is a way to transmit digital signals upon the radio. It can be considered as one of the first wireless digital transmissions, somehow a predecessor of wireless Internet. Its transmission rate is quite low (something like 60 characters per minute), but it uses a solid modulation, meaning that the signal can be decoded also with high values of noise and interference.

RTTY software

The programme I use for decoding RTTY transmissions is MMTTY, up to know the only free software I found. Then I plug the line-out of my receiver to the mic-in of my laptop to get the signal.

RTTY bands

Here follows a list of sub-bands used by radioamateurs transmitting in RTTY, as suggested by AA5AU on his wonderful page Getting Started on RTTY. Usually transmission is at 45.45 baud (60 wpm) and 170 Hz shift for the two tones (2125 and 2295 Hz).

10 meters 28080 to 28100 kHz
12 meters 24910 to 24930 kHz
15 meters 21080 to 21100 kHz
17 meters 18100 to 18110 kHz
20 meters 14080 to 14100 kHz
30 meters 10120 to 10150 kHz
40 meters 7025 to 7050 kHz
80 meters 3580 to 3600 kHz
160 meters 1800 to 1820 kHz

A regular service in standard RTTY (ITA-2 alphabet) is the German Meteorological Service or DWD. The bandplan, available from their website, is reported here below:

Callsign Frequency Speed/Shift Time
DDH47 147.3 kHz 50 baud/85 Hz 05.00 – 22.00 UTC
DDK2 4583 kHz 50 baud/450 Hz 00.00 – 24.00 UTC
DDH7 7646 kHz 50 baud/450 Hz 00.00 – 24.00 UTC
DDK9 10100.8 kHz 50 baud/450 Hz 00.00 – 24.00 UTC
DDH9 11039 kHz 50 baud/450 Hz 05.00 – 22.00 UTC
DDH8 14467.3 kHz 50 baud/450 Hz 05.00 – 22.00 UTC


RTTY resources on the net:

One thought on “RTTY

  1. John

    Hi
    I cannot get mmtty to decode DDH47 147.3khz
    are there any special settings?

    cheers

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