Maybe this will help folks understand how it works and also make other folks
understand why contest mode was necessary in the first place. The only thing
in the manual about Contest Mode is this:
--------------------------------
The FT8 and MSK144 modes support a special feature allowing convenient
transmission and acknowledgment of four-character grid locators, the required
exchanges in most North American VHF contests. With this Contest Mode enabled,
WSJT-X supports messages of the form W9XYZ K1ABC R FN42 by converting the grid
locator to that of its diametrically opposite point on Earth. The receiving
program recognizes a locator implying a distance greater than 10,000 km, does
the reverse transformation, and inserts the implied “R”. Obviously, this mode
should not be used on the HF bands or under other circumstances where
world-wide propagation is possible.
----------------------------------------
This leaves a lot unsaid. From the manual description all WSJTX messages are
set in a 72 bit format. The mode speed (fast or slow) determines how many
times that 72 bit message is repeated in the transmission period. In FT8 its
repeated twice. If a single 72 bit message is received with no errors
according to the FEC (forward error correction method) then it will decode. No
partial decodes are allowed Joe did not include contest mode in the original
alpha and beta releases and it was added back some time ago well before (at
least a year) FT8 was invented after a lot of stations complained about
problems getting grids across on MSK144 since grids were only included in TX1
and TX6. If you scheduled a MSK144 QSO during a contest as we often do on Ping
Jockey then both stations would call each other with TX1. The standard
operating practice says as soon as you receive TX1 you respond with TX2. Well
in that scenario only one of the stations would actually receive a grid and
this was not acceptable since both stations have to exchange grids (but NOT
reports) in a contest. Good practice also mandates the exchange of
acknowledgements or R. The only way to legally do it then was to have both
stations call CQ even on a prearranged sked since TX6 had a grid in it, then
when one received TX6 he would then switch to TX1 and the QSO would progress.
But it really wasn't the whole answer since you really never acknowledge you
received the other guys grid; it was just implied. This also added another two
sequence time interval to the QSO and both TX2 and TX3 were superfluous to the
contest QSO which only requires the exchange of grids. Adding unnecessary
sequences was a big burden since adequate meteor burns can be scarce
(especially on 2M) and sometimes you can go many minutes without getting a ping
that decodes. Additionally the older WSJT10 FSK441 mode did have an alternate
GRID only message format that was used during contests. So there was a
problem.
-----------------------------
So Joe want back to the drawing board to try and accommodate the requests from
contesters (myself among them) to make this work better and shorter in MSK144
like it used to in FSK441. But the 72 bit message format that is the basis of
all WSJTX transmissions did not allow that many bits to get the message with
the format W4XXX K2DRH R EN41 encoded to be transmitted in 72 bits. So Joe had
to do a work around or a kludge (remember at this point in time Joe was pretty
much doing all the programming) and he had to do it quick because another
contest was pending (think he did it between June and CQWW VHF but my memory
may be off). So he came up with using the 180 degree around the world grid
equivalent (or reciprocal grid) being transmitted to keep within the 72 bit
format ... and then on the RX side of the program also in contest mode that is
translated to the correct grid on the screen. So this really was a solution to
an actual problem, albeit a messy one that creates compatibility issues between
stations that are not in contest mode. This translation to the alternate grid
cannot be implemented in the "normal" report mode because then it could not be
used on HF or even on 6M when multihop DX could be received.
---------------------------------------
So why was contest mode put in FT8 and why was it necessary to put the
activation of it in the VHF UHF Microwave settings? We were the ones who
wanted to use FT8 in a VHF contest setting so contest mode was grandfathered in
from MSK144 during the beta testing stage. As soon as it was many HF ops using
FT8 failed prompt stupid and tried to use it to shorten their QSOs despite the
warnings that it could not be used for international DX. They complained so
much about the " funny grids" and incompatibility with auto sequencing the
programmers "hid" it from them where only the VHFers who would use it could
find it. During a contest if a station CQs on FT8 in non contest mode and gets
a TX1 reply they exchange grids and the QSO is technically valid but the grids
are not really acknowledged as good practice would demand plus it takes an
extra sequence with superfluous reports to complete the QSO. If the other
stations opts to send TX2 and replies in "normal" or non contest mode then the
CQ station does not get a grid. If the other station calls him while he is
engaged in another QSO in "normal" mode then they did not actually exchange
grids both ways during their QSO either; even worse if he calls with TX2. And
FT8 QSOs can be scheduled too ... around here we do it on 2M. Contest mode on
FT8 solves all these issues, works just fine when both stations use it and
satisfies all requirements. So saying that contest mode is a solution in
search of a problem is inaccurate and a misunderstanding of the issues
involved. I just wish it didn't have compatibility issues with "normal" mode
and we didn't have to have this whole conversation.
-------------------------------------
73 de Bob2
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