locked #FST4W Premature Decode #FST4W


Andy Talbot
 

I was trans,otting on FST4W-1800 and spotted that one station DL0AO
reported my first transmission that had started at 1900z when the clock was
showing 192930z, several tens of seconds BEFORE the transmission had
finished
Didn't know the decoder worked that way. I know the raw data symbols are
transmitted first in the transmission, before any parity bits. So if the
first 74 bits + CRC - a bit under half the symbols - in the message are
copied correctly and the CRC checks-out, there is no need to monitor any
more of the transmission.
And it can report a decode immediately.

The report was -28dB, so more than 10dB above the threshold - good
enough S/N for error-free copy.

It also means the software is actually looking at the data while it is
arriving, rather than just at the completed saved .WAV file.

Didn't realise that

Andy
www.g4jnt.com