On 22/07/2017 03:57, Tsutsumi Takehiko wrote:
I am wondering why FT8 does not support "CQ XXX" and "QSY 50.280"
sequences which MSK144 supports concerning "split operation" topic
discussed in this thread.
I believe above two sequences intentionally bring the split operation to
out-band, which is beneficial for DX-peditionners.
Do you know any reason why FT8 does not include these features?
Hi Take san,
it could be enabled along with "Settings->General->Enable
VHF/UHF/Microwave features" but currently the focus is on improving the
FT8 multi-signal decoder in typical 6m and HF usage where many signals
are decoded together. This has distinct benefits as everyone sees all
signals, give or take propagation differences, and spots to services
like pskreporter and hamspots have maximum value. FT8 was designed to
meet a need seen during fleeting 6m multi-hop Es openings, it has also
clearly found favour with those less than satisfied with the slow pace
of JT65 and JT9 QSOs on HF as well, neither of these styles of operating
will benefit greatly from a set up that moves each QSO to a separate
frequency.
Because of the strict two period format of the JT/FT modes there is an
obvious opportunity for QRM elimination from local stations by
coordinating timing during DX openings, i.e. all local stations at one
end of the path agree to use one period and the DX stations at the other
end use the other. This can either be semi formal, e.g. opening to west
then call even, opening to east then call odd, or it can be less formal
where stations simply congregate with other local stations on the same
period and hope that the DX stations do the same. Simply listening and
choosing the same period as the majority of other stations seeking DX
can sometimes gets everyone sorted out.
I have often though that using two frequencies might also be useful on
VHF and up bands, one for local contacts and one reserved for
intercontinental DX that has an agreement on which period to use.
The "CQ NNN ..." mechanism is of most value for scatter modes when it
becomes busy, for example random MS working in a major shower. MS modes
fill the receiver bandwidth and the occupancy per channel tends to be
much lower therefore QSYing to complete a QSO makes much more sense.
Having said that, the nature of MS reflections with a cone like path
allows a considerable sharing of a single frequency since the projection
of the path cone onto the earth's surface allows multiple pairs of
stations to operate without signal overlap (time division multiplexing
rather than frequency division multiplexing) i.e. one MS reflection may
only serve one pair of stations while the next may serve a completely
different pair on the same frequency.
73
Bill
G4WJS.
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