Added description of MSK144 Sh messages.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7010 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
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Joe Taylor 2016-08-06 14:30:33 +00:00
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@ -38,6 +38,17 @@ repeated without gaps for the duration of a transmission cycle. For
most purposes we recommend a T/R cycle duration of 15 s, but 5 s and
10 s sequences are also supported.
MSK144 short ("Sh") messages are intended primarily for 144 MHz, where
most pings are short. These messages do not contain full callsigns;
instead, they contain a hash of the entire transmitted message along
with a report. They are not encrypted -- the report is sent in the
clear along with the hash. Short messages are fully decodable only by
the station to whom they are addressed, as part of an ongoing QSO,
because only then will the received hash match that calculated using
the known strings for "My Call" and "DX Call" and the received report,
RRR, or 73. If you are monitoring someone else's QSO, you will not be
able to decode its Sh messages.
An MSK144 signal occupies the full bandwidth of a typical SSB
transmitter, so transmissions are always centered at an offset of
1500Hz. For best results, selectable/adjustable Rx and Tx filters