by Steve Anderson » Thu Feb 25, 2021 1:41 pm
Updated design coming on nicely... now I have to turn my attention to demodulation. There's three (maybe more) ways to do it, 1) Zero-crossing, 2) FM demodulation, 3) In software using mixing, FIR filters and a bit of calculus...
The MkI used #2, the results I think where quite good considering the relative simplicity of the design. I did experiment with #1, it worked OK, better in some areas, marginally less so in others, sadly I can't find the code I wrote for it. or even the concept as to how I did it...
.... I've yet to try #3.
Two of these methods may require an external demodulator, #2 and #3. Even #1 may benefit by using an external arrangement. I'm still dwelling on this but I don't want to spend too much time on it.
I may go with #1 first, and try the others later...
Steve A.
A fourth method that slipped my mind #4) PLL (Phase Locked Loop). Either analogue (e.g. our beloved 4046) or an ADPLL (All Digital Phase Locked Loop). The latter holds a lot of promise, but the maths required, "Does me 'ead in"...translation from 'saaf londin' speak, it's somewhat challenging...
Another musing, a blend of means is also a possibility...more to come...