On Jan 27, 2010, at 1:32 PM, Robert Chudek - K0RC wrote:
> Overall during a contest, few contacts are made at the noise floor.
Yes, that is my impression also.
I think that the vast majority of contest contacts are made way above the FSK
decoding thresholds. A couple of dB isn't going to be noticeable unless you
actually switch back and forth when print becomes marginal at the higher baud
rate. With the VE3NEA plots, we are mostly operating on the far right side of
his curves.
The only snag is that the ones that are hard to copy are often new mults :-)
:-).
> If MMTTY was meant to operate at only 45.45 baud, there wouldn't be a menu
> with other speeds available!
In the case of cocoaModem, it does not even use a menu for baud rate. It has
fields where you can type any arbitrary baud rate you wish to use You can type
in 45.0 instead of 45.45 as baud rate to match some of the commercial FSK
interfaces. Mark/Space/shift work the same way also, completely arbitrary.
But, whatever you want to experiment with, keep the shift under 1 kHz in the
USA so the FCC does not get mad at you :-). In the US, you are also not
allowed to use any code that has not been openly published (by you or by
someone else). So, don't try using a 8/5 Hamming code to transmit error
corrected Baudot FSK unless you let everyone know ahead of time :-).
If you hate the Baudot LTRS/FIGS aliasing of characters, you can also
experiment with the FCC approved (back in 1980) 7-bit ASCII RTTY protocol that
you can run on Amateur HF at up to 300 baud. The "standard" was 110 baud, if I
remember correctly. The 110 baud rate more than makes up for the fact that you
transmit about 28% more bits. But you also don't need to transmit LTRS or
FIGS, so for exchanges with a lot of mixed letters and numerals, the overhead
is not anywhere close to 28%. The callsign alone often has one LTRS and one
FIGS, unless you are an 4X4 station, in which case it is worse :-). No
LTRS/FIGS shifting, plus lower case and European characters, too, like the
PSK31 boys.
Real experimentation seems to nowadays be done on other digital modes than
RTTY, of course.
73
Chen, W7AY
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