The PIC/DDS beacon source is now running, and it's being tested on air for the first time with FSTW-120, -300 and now -900
There's just have one issue to sort out. I generate the Gaussian glide by using just two adjacent symbols and adding their weighted components based on a lookup table, sampled at 64* the sample rate.
Doing it like that means each session starts half a symbol late. For the faster modes this doesn't matter, it's less than a second on DT. On FSTW-900 the resulting delay of half a symbol is 2.8 seconds - which the decoder seems able to cope with but on -1800 the delay, DT, becomes 5.6 seconds which doesn't work.
I can sort this by doing the job properly, and adding weighted versions of three symbols, last, this and next. A few more lines of code, but easy enough to do
and.. as I write ... just checked WSPRNET, and there's a decode of the first -900 signal off air. It works !