Hi Rik well done, as an old RTTY operator (BC....Before Computers!), I had
wondered about FSK. As far as I could see from the weak signals I have
looked at on waterfall dispays, there could be a extra benefit. You would
get a little bit of extra edge when decoding as it would be logically
'dot-and-not-dash'. So there would not be quite the same decode problem
were at present the static cuts a dash into two dots. The frequency
discrimination would take care of that (or the static would wipe out the
element completely). It certainly would be worth trialling.
Cesare mentions frequency stability, but I transmitted RTTY 170Hz shift on
432 MHz in the 1970s by FMing a crystal oscillator. I believe that this
technique would be adequate for simple (the best kind) transmit systems on
136. Easier still if you are already using a crystal mixer exciter.
I think as Cesare says we need an absolute definition of which element will
be the higher RF frequency. Your call Rik!
73 de Alan G3NYK