[Lf] LF: Where next?]

[Andre' Kesteloot]

Mike Dennison wrote:

> > ..................... 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