[RTTY] Tinyfsk, 2Tone and USOS

[Kok Chen]

On Sep 29, 2015, at 11:01 AM, Charles Lind wrote:

> Why is it if I transmit using MMTTY/simple transistor interface I get no requests for repeats, and checking with another rig on receive loaded only with MMTTY it prints correctly when I send "599 05 NY NY", but when I switch to 2Tone/Tinyfsk 

Probably because you have set MMTTY to send using "no USOS."  And the receiver was also using a non-USOS decoder.

Both TinyFSK and 2Tone (read their code if you don't believe me) forces USOS transmissions as default.  As a result, a non-USOS receiver will have problems with exchanges sent by TinyFSK and 2Tone that use space characters as separators from the FIGS symbol set to the LTRS symbol set.

For people who are not familiar with RTTY, a USOS system will send "599 05 NY NY" as

<FIGS>599<space><FIGS>05<space>NY<space>NY"

while a non-USOS transmitter sends:

<FIGS>599<space>05<space><LTRS>NY<space>NY"

I'll leave it as an exercise for the reader to decode the two above streams on (i) a USOS receiver and (ii) a non-USOS receiver.

73
Chen, W7AY