•
50 bauds
•
signals at 915 and 1365 Hz
•
try 4581.865 kHz, 7644.860 kHz, 10099.660 kHz, 11037.860 kHz or 14466.160 kHz
RTTY TX (Experimental)
Using CW Keyer Input
•
Switch CW Keyer Mode (CW menu) to Iambic or Ultimate
•
Set CW TX RX delay (CW menu) high enough so that RTTY keeps transmitting
between your Morse letters
•
As soon as you start using the keyer, your decoded Morse code will be sent out
as RTTY (or idle RTTY is sent)
Using USB Keyboard Input
Simple RTTY TX via USB Keyboard now possible, most but not all USB keyboards work.
Keyboard layout is QWERTY, no matter what the keyboard says.
•
Switch CW Keyer Mode to Straight (disables RTTY CW Keyer Input)
•
Now select desired RTTY mode
•
Hit F1 on keyboard to start TX (or press PTT)
•
Enter text, text is immediately sent out
•
Hit F2 on keyboard to stop TX (or press Tune twice)
•
You can also enter text before you press F1, it is stored and sent when you start
TX.
Theory
RTTY is a simple FSK (frequency shift keying) mode which transmits digital data at
relatively low speeds without error correction. We use a simple but apparently quite well
working decoder based on a DSP tutorial written by Norbert, HA2NON, adapted and
extended for use in the UHSDR firmware. The demodulator filters both frequencies and
passes the energy difference through a simple 50Hz filter. The resulting signal is passed
to a digital PLL which handles the bit decoding timing and a symbol decoder which then
decodes the bitstream into RTTY characters.
A nice example for a digital mode which existed for a long, long time.
