..................... One such candidate could be the Steve Onley's FDK. I
know that, theoretically, PSK can have an advantage over non-coherent
FSK, but this doesn't take into account phase distortion over very
long paths. But I will leave to others to discuss about the pros and
cons of the two methods.
73 Alberto I2PHD
A factor that is often ignored when comparing PSK08 (for instance)
and QRSS is the difference between relying on a machine to
interpret the results and using the brain. The spectrogram-type
programs do wonderful work but the final 10dB or so is down to the
brain deciding what is a valid signal and what is not, then deciding
whether it makes sense or not.
We really would have a winner if we can combine the obvious
theoretical advantages of using FM (or phase mod) rather than AM,
especially when noise is a significant limiting factor, with the
advantages of a display that allows the brain to add some dBs by
intelligently interpreting the result.
For instance, how about produce a display that is the result of
subtracting the signals and noise in a given audio band, with the
signals and noise in another band of the same bandwidth. This might
provide a means of reducing the effect of wideband noise such as
static (but not random noise) on a conventional mono-frequency
transmission by subtracting the noise in the 'no-signal' band from
the band containing the signal. It might also provide a 'comparitor'
effect so that FSK signals can be better detected - for a given time
period, if the output of 'channel A' is bigger than the output of
'channel B' then it is a binary '1'; if the other way round it is a binary
'0'.The important thing is to resist the temptation to feed this into a
machine that tries its best to work out whether it is a valid character
or not - this is the bit that the brain does better.
Mike
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