--- In digitalradio@yahoogroups.com, "Patrick Lindecker" <f6...@...> wrote: > A synchronous RTTY under Windows is possible with a standard symbol > synchronization (with or without a PLL which can be seen as the "digital > flywheel"). However, the stop bit (1.5 symbols) complicates all as it is not > an integer multiple of the symbol length. > > Now, RTTY must be supposed to be asynchronous to be compatible with all RTTY > apparatus and programs. Let's work on more modern modes...
I did some work earlier with "compatible synchronous RTTY" using 7.00 unit start-stop code, to make it easier to synchronize. Even mechanical TTY machines can easily receive 7.00 unit code. I built a transmitting converter that would send the 7.00 unit code, and insert fill characters (LTRS or FIGS) if there was no input character available when one was called for. Another ham was working on the receiver - I don't know if he ever got it working. Then years later K6STI did his "digital flywheel" and he said it didn't matter that the character length was not an integral multiple of the bit length so long as the character length was constant. Which required transmitting "diddle". But I fully agree about more modern modes. Last night I was copying a couple of RTTY stations, pretty good copy except for QSB, and one of them was using 1KW and the other using 500W. And back in the glory days of RTTY we were all trying to run that kind of power. I have a big TMC kilowatt transmitter gathering dust out with all the TTY machines. There is an amusing explanation for why TTY uses a 7.42 unit code (in the U.S.) but I'll forbear to tell it unless someone asks. Jim W6JVE
