Hello Jim and group,
Thanks for the "Variable PSK" thoughts - will take some more time to
thing about them again.
We (that's Markus DF6NM and myself) came to similar conclusions that ...
- with an optimum-shaped "slow" phase transition you end up at MSK
- if one doesn't attempt to write the "ultimate (matched) decoder" for
MSK, it isn't sooo tough (but..)
- some clever ideas for synchronisation at very low symbol rates must be
implemented
(one of them being simply to synchronize it "manually" looking at a
radio-controlled clock).
As I see it, a fully automated digital mode which does "everything"
itself is not favourable compared to CW (oh but please don't let us
start debates on this again), and even QRSS / DFCW and other "visual"
modes have their charm - the operator's brain wants to be involved in
the decoding process.. but that's just a personal opinion.
As Brian wrote..
So, in the absence of a narrow-band medium-speed keyboard
mode that can be transmitted through a non-linear amplifier,
is it time to review how we make best use of our 2.1 kHz ??
<
Help may(!) be on the way, most likely a slow variant of G3PLX's PSK31
in QPSK mode (which is already possible to send and decode), turned into
MSK "somehow" to remove the need for a linear transmitter. This may be
achieved by delaying the signal in the quadrature phase branch (of the
modulator and demodulator) for a half symbol time, and shaping the
pulses before the modulator. This way there will be no more 180° phase
transitions in the modulated audio signal, only 90° phase changes, and
the amplitude will be constant by means of the data pulse shaping.
I have no idea if, when, and how this will be implemented yet, it all
depends...
Greetings,
Wolf DL4YHF .
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