[UK-CONTEST] RSGB Contest Committee

[David G3YYD]

I would point out that 75 baud on 80m evenings is very bad news. The 
problem is that 75 baud suffers significant inter-symbol interference 
due to multipath propagation that occurs on 80m either side of dusk. At 
times, 75 baud signals will be strong but have so many errors that QSOs 
will not be possible or require many repeats. It is much better to stay 
with 45.45 baud as it is rarely made unworkable by multipath 
propagation. It is one of the reasons that 45.45 baud was favoured over 
50 baud. The 22 millisec element being more robust that the 20 millisec 
element. The other being that the USA commercial standard was 45.45 baud 
although nearly every other country in the world used 50 baud commercially.

If use is to be made of 75 baud then avoid times around dusk or move the 
contest to another band which suffers less multipath propagation. This 
would not fit in with the CC programme. I would suggest that a 6m or 
above Data contest would be ideal for 75 baud or higher. Something to 
make the VHF/UHF spectrum club contests more challenging?

If faster RTTY QSOs are required then lets minimise the amount of stuff 
that people send in their macros that would save more time than going to 
higher speed. Also shorten the TX stop bit from 1.5 element length to1 
element. This is a settable value in MMTTY and probably in other decoders.

I would point out if increase in Data CC QSO rate is needed then get rid 
of PSK31 it has lower rate than 45.45 baud RTTY, but then that would 
reduce the skill challenge of Data CC. Also when multipath kills 75 baud 
one thing for sure PSK31 will not be workable either. Do we really wants 
some evenings when very few QSOs even though the signals are strong?

Remember that CC runs from January to July and so experiences the 
complete set of propagation changes as the sun illumination changes. 
Specified data modes have to be robust over the complete propagation 
set. What works in July may not work in March or January or ....

David G3YYD

On 07/08/2010 11:16, Chairman, RSGB Contest Committee wrote:
> DATA CC CONTESTS on 80m
>
>    
>> >    RTTY is the major contesting data mode and up to now has
>> >    been at 45.5Bauds. ... the BARTG 75 Baud contest, which
>> >    a lot thought a waste of time, it has proven to be very popular.
>> >    ... would be interesting to see how 75Baud RTTY performed
>> >    ... extremely simple to go from one speed to another and the
>> >    same narrow CW filter can be used.  ... enable scores to be
>> >    increased, in the small amount of time spent on RTTY.
>> >    [I would] not suggest an increase in PSK speed as the
>> >    bandwidth is already very small
>>