Hello Barry,

Very nice THOR signals overview thanks a lot!


The tone shaping is, as you have expressed, a means to keep the bandwidth ot a minimum.

But it was requested for a quite specific reason: a sharp edge of the signal when starting a message does, based on experience, make the initial synchronization more difficult, leading to some lost characters at times. I assume this happens because the decoder does not get the intended single (idle) tone frequency as a first input, but an ambiguous mix of frequencies (which is of what such a transient 'step function' consists of).

So it would be quite interesting to verify, while you run your nets, whether the initial text errors, whenever a station starts a message, have been reduced due to this short signal ramp. I had checked this effect and idea of a startup ramp when I had made off-air recordings of different MFSK signals that still had a sharp start and where the first bits of a message were not properly (or at least reliably) read. Adding a little ramp at the start (by editing the recorded audio) usually got FLdigi to decode the same message flawlessly from the beginning. So it's basically a recommendation to help facilitate initial synchronization. But of course, it only helps when transmitting stations actually use the latest FLdigi version (with the shaped signal startup and ending). Should you wish to try different options, you can adjust the length of the ramp from 0 ms (sharp = similar to previous FLdigi versions) up to 500 ms (very soft), with a default of 100, very well chosen by David. This user setting is at Menu - Config - Modem - General - 'Raised cosine startup shape' (it affects both signal startup and ending).


If you make any on-air observations regarding this feature, please let us all know...


Thanks and best regards

Tobias
.-.-.