$50SAT (Eagle-2) RTTY telemetry



Use FLDIGI for decoding. FLDIGI needs to be set-up correctly, the settings are; set for custom carrier shift, 630Hz shift, 8 (ascii) bits per character, none parity, 1 stop bit, fast AFC. The RTTY decoder in FLDIGI then needs to be positioned correctly to allow the ASCII to be decoded, the FSK uses two tones about 630Hz apart. It was designed to use FLDIGI with the tuning point of the radio set to produce the two shifted tones centred on a 1kHz shift. To this end, if the radio receiver is tuned such that the reception frequency is in the centre of the FM Morse (clearest signal) and you then shift the receiver to LSB mode the two FSK tones should appear at the right width apart and at approximately 685Hz and 1315Hz.
To aid radio tuning and to assist in the positioning of the FLDIGI decode cursor (the red lines) the FSK RTTY transmission is prefaced with a sequence of 11 short FSK pips transmitted with an offset approximately 1kHz from the RFM22 centre frequency, so they should be heard as 1khz tones.

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