On 23/04/2019 16:40, Tom Melvin wrote:
I don’t want to assume so will ask - FT4 aimed at ‘Contest Friendly digital
modes’ - cool - BUT will it cater for the pile of weird contest rules that are
out there. The abundance of requests for QSO Parties, Field Days where
non-standards messages. Heck for us UK VHF types - 6 character Locator squares
etc.
Hi Tom,
the FT8 payload protocol is identical to that of FT8 and MSK144, that
means it can support each of the contest modes available on the
"Settings->Advanced->Special operating activity" panel. That already
includes EU VHF Contest mode which is designed to match Region 1 VHF and
up contest rules requiring exchange of a 6-digit Maidenhead locator,
report and serial number. With respect to generic contest support, that
will not happen due to the constraints of fitting the messages into the
77-bit payload. There will be many requests to support various contest
but that is not possible since the ones we have are "baked in" to the
message encoding and restricted to exactly and rigidly the required
exchange information. For example a naive observer might think that the
US states and VE provinces used in the RTTY Roundup contest exchange may
be used for some other contest that uses a different set of regional
abbreviations, that is not how it works as the codes are not sent as is
but compressed to an index number only. A less naive observer might then
say well that's ok, just change the translation of the indexes to
contest X's exchange requirements, but we are very unlikely to do that
because there is no space in the message to encode which set of mappings
are to be used and chaos will follow with decoded messages being widely
misinterpreted.
Here is a simple case study of a request to support a particular
contest. The ARRL Winter Field Day (WFD) is almost identical in exchange
requirements as the ARRL Field Day (FD), the only difference is that WFD
uses a different set of class category codes, (I)door, (O)utdoor, and
(H)ome. So initially it seems trivial to use 'I', 'O', and 'H' instead
of the normal FD 'A' thru 'F' class category codes. This doesn't work
for two reasons, firstly the codes are hard coded, and secondly even if
they weren't they all have to fit into three bits. So we could change
the encoding and decoding to accept 'A' thru 'F' *and two other codes*
but there is no room for a third, it is simply not possible to encode
the nine required values in three bits. All we could offer to the many
that requested support for WFD is that three of the 'A' thru 'F'
categories be accepted by the WFD organizers as valid substitutes for
their 'I', 'O', and 'H' categories. Of course they didn't accept that,
why should the software for a new digital mode enforce a change in the
long standing rules for an established contest. Anyway either because
our unavoidable technical intransigence, or more likely because a
strictly formatted digital mode exchange is not really in the sprit of a
FD w/e, they simple changed the rules such that FT8 is not allowed for
valid WFD contacts.
73
Bill
G4WJS.
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