Time efficient code]

[Andre' Kesteloot]

Rik Strobbe wrote:

> If we want to develope a new 'code' for a time effecient mHz bandwidth
> modulation first thing we should do is to make a list of requirements.
> My list would be :
>
> - suitable with non-linear amplifiers :
> for sake of efficiency and simplicity of the amplifier
>
> - be able to transmit at least 45 different 'characters' :
>
> - if we want to use non-linear amps we can only transmit one 'tone' at a
> time, so each character needs to be transitted a a sequence of 'tones'. The
> more 'tones' you use the shorter the sequence per character will be but the
> larger the required bandwidth, so we will have to find a compromize between
> bandwidth and speed.
> eg. 47 characters can be transmitted with 7 tones and 2 sequences per
> character (49 posibilities) or as 4 tones and 3 sequences per character (64
> posibilities).
>
> An important question is : is it worth to make things that complicated ?
> Assume the transmission speed is 60 seconds dotlength. In that case the
> time needed to transmit 'CQ ON7YD K' would take :
>
> 114 minutes in QRSS
> 40 minutes in DFCW
> 30 minutes in '7 tone mode' if we have a space between characters
> 20 minutes in '7 tone mode' if we have no space between characters
> 40 minutes in '4 tone mode' if we have a space between characters
> 30 minutes in '4 tone mode' if we have no space between characters
>
> >From the above is clear the step from QRSS to DFCW is significant (time
> reduced to 35%), but the difference between DFCW and the 'multi tone modes'
> is between nil and 50%, so we should have to go to a rather complicated
> system (7 tones, no spacing) to have a significant gain.
>
> Other opinions please ...
>
> 73, Rik  ON7YD