ARLA/CLUSTER: Modo Digital FT8 via satélites: Cuidado ao usar modos digitais de alto ciclo de trabalho via satélite, adverte a AMSAT News Service

[João Costa > CT1FBF]

Caution urged in using high duty cycle digital modes via satellite

A report in ANS-288 discussed an experiment operating with the WSJT-X FT8
via satellite. Satellite operators have gained more experience with this
mode over this past week

As a result of on-the-air observation other satellite users planning to try
FT8 or MSK144 modes via satellite are encouraged use caution using these
modes and possibly avoid their use completely in light of problems.

*Dave, KG5CCI* wrote, "He noticed a very hard time getting into the
transponder. The pass was nearly overhead, and the 3w-4w that is normally
sufficient was barely cutting it. I also noticed it was 'up and down' alot,
whereas some moments it was easy to get in, then it would be nearly
impossible. There were also pockets of 'noise' all over the transponder,
that sounded somewhat digital, but I just couldn't place them." Further
investigation revealed that an MSK144 signal in the transponder passband
was causing the problems.

*Matthew, NJ4Y* noted, "Experimentation isn’t the problem, too much power
is. It’s bad enough on SSB, worse with CW, and killer on constant duty
cycle modes like FT8."

To gain a full understanding of the situation readers are encouraged to
follow the amsat-bb message thread which can be accessed at:
http://www.amsat.org/pipermail/amsat-bb/2017-October/064896.html

Source: AMSAT News Service
http://www.amsat.org/mailman/listinfo/ans
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