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Update text in User Guide related to *NA VHF Contest Mode*.

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git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@8046 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Joe Taylor 2017-08-29 14:01:55 +00:00
parent ff623873b0
commit 683e35fdec
3 changed files with 25 additions and 22 deletions
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30
doc/user_guide/en/protocols.adoc
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@ -40,11 +40,22 @@ additional information is sent in place of the grid locator or by
encoding additional information into some of the 6 million available
slots mentioned above.
Finally, the message compression algorithm supports messages starting
with `CQ AA` through `CQ ZZ`. Such messages are encoded by
sending `E9AA` through `E9ZZ` in place of the first callsign of a
standard message. Upon reception these calls are converted back to
the form `CQ AA` through `CQ ZZ`.
As a convenience for sending directed CQ messages, the compression
algorithm supports messages starting with `CQ AA` through `CQ ZZ`.
These message fragments are encoded internally as if they were the
callsigns `E9AA` through `E9ZZ`. Upon reception they are converted
back to the form `CQ AA` through `CQ ZZ`, for display to the user.
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.
To be useful on channels with low signal-to-noise ratio, this kind of
lossless message compression requires use of a strong forward error
@ -289,15 +300,6 @@ with constant envelope, equivalent to a Minimum Shift Keying (MSK)
waveform. Frame duration is 72 ms, so the effective character
transmission rate for standard messages is up to 250 cps.
Contest Mode in MSK144 conveys an additional acknowledgment bit (the
"`R`" in a message of the form `W9XYZ K1ABC R FN42`) by using the fact
that meteor scatter and other propagation modes usable with MSK144 are
generally effective only out to distances of order 2500 km. To convey
the message fragment `R FN42`, WSJT-X encodes the locator as that of
its antipodes. The receiving program recognizes a locator with
distance greater than 10,000 km, does the reverse transformation, and
inserts the implied "`R`".
MSK144 also supports short-form messages that can be used after QSO
partners have exchanged both callsigns. Short messages consist of 4
bits encoding R+report, RRR, or 73, together with a 12-bit hash code

7
doc/user_guide/en/settings-advanced.adoc
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@ -31,9 +31,10 @@ IMPORTANT: For the health of your T/R relays and external
preamplifier, we strongly recommend using a hardware sequencer and
testing to make sure that sequencing is correct.
- Check *FT8 and MSK144 Contest Mode* to enable generation and
auto-sequencing of MSK144 messages with four-character grid locators
in place of signal reports.
- Check *FT8 and MSK144: NA VHF Contest Mode* to enable generation and
auto-sequencing of messages using four-character grid locators in
place of signal reports, as required for most North American VHF
contests.
- Check *x 2 Tone spacing* to generate Tx audio with twice the normal
tone spacing. This feature is intended for use with specialized LF/MF

10
doc/user_guide/en/vhf-features.adoc
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@ -279,11 +279,11 @@ messages at 50 or 70 MHz. At these frequencies, most pings are long
enough to support standard messages -- which have the advantage of
being readable by anyone listening in.
- A special *Contest Mode* for MSK144 can be activated by checking a
box on the *Settings | Advanced* tab. This mode is configured
especially for VHF contests in which four-character grid locators are
the required exchange. When *Contest Mode* is active, the standard QSO
sequence looks like this:
- A special *VHF Contest Mode* for FT8 and MSK144 can be activated by
checking a box on the *Settings | Advanced* tab. This mode is
configured especially for VHF contests in which four-character grid
locators are the required exchange. When *Contest Mode* is active,
the standard QSO sequence looks like this:
CQ K1ABC FN42
K1ABC W9XYZ EN37