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Re: [VHFcontesting] How and Why Contest Mode Evolved

To: vhfcontesting@contesting.com
Subject: Re: [VHFcontesting] How and Why Contest Mode Evolved
From: Dan via VHFcontesting <vhfcontesting@contesting.com>
Reply-to: k1to@aol.com
Date: Thu, 14 Jun 2018 13:50:08 -0400
List-post: <mailto:vhfcontesting@contesting.com>
 Interesting stuff, Bob.

From another angle, we went through last June with JT65 as the digital mode of 
choice for DX.  The minimum 4-minute QSO time was longer than many openings 
lasted, thus there was a push for a quicker mode.  Not sure why the 
already-existing JT9 with its 15-second intervals wasn't promoted for this, but 
I think that was also a strong impetus for the creation of FT8.  

73, Dan

 

 

-----Original Message-----
From: k2drh <k2drh@frontiernet.net>
To: VHF Contesting Reflector <vhfcontesting@contesting.com>
Sent: Thu, Jun 14, 2018 12:14 pm
Subject: [VHFcontesting] How and Why Contest Mode Evolved

 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_______________________________________________VHFcontesting mailing 
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