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Add info on 28-bit integers used for standard callsigns.

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Joe Taylor 2018-06-23 11:54:40 -04:00
parent 7266d407ff
commit 35b53766cb
1 changed files with 16 additions and 4 deletions
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lib/77bit/77bit.txt
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@ -1,6 +1,9 @@
Proposed new message types have a 77-bit payload: 74 information bits Proposed new message types have a 77-bit payload. For most purposes
and 3 bits for "message type" i3. Type 0 uses only 71 information these are interpreted as 3 bits (i3) for "message type" and 74
bits, releasing another 3 bits (call them n3) to define 8 sub-types. information bits. Any message type that uses fewer than 74
information bits can assign the remaining bits to define message
subtypes. For example, Type i3=0 uses 71 information bits and the
remaining 3 bits, here called n3, define 8 subtypes.
---------------------------------------------------------------------------------- ----------------------------------------------------------------------------------
i3.n3 Example message Bits Total Purpose i3.n3 Example message Bits Total Purpose
@ -11,7 +14,8 @@ i3.n3 Example message Bits Total Purpose
0.3 WA9XYZ KA1ABC R 16A EMA 28 28 1 4 3 7 71 ARRL Field Day 0.3 WA9XYZ KA1ABC R 16A EMA 28 28 1 4 3 7 71 ARRL Field Day
0.4 WA9XYZ KA1ABC R 32A EMA 28 28 1 4 3 7 71 ARRL Field Day 0.4 WA9XYZ KA1ABC R 32A EMA 28 28 1 4 3 7 71 ARRL Field Day
0.5 0123456789abcdef01 71 71 Telemetry (18 hex) 0.5 0123456789abcdef01 71 71 Telemetry (18 hex)
0.6 0.6
0.7
1 WA9XYZ/R KA1ABC/R R FN42 28 1 28 1 1 15 74 Standard msg 1 WA9XYZ/R KA1ABC/R R FN42 28 1 28 1 1 15 74 Standard msg
2 TU; W9XYZ K1ABC R 579 MA 1 28 28 1 3 13 74 ARRL RTTY contest 2 TU; W9XYZ K1ABC R 579 MA 1 28 28 1 3 13 74 ARRL RTTY contest
@ -29,6 +33,13 @@ In case we need them, later:
NB: three 74-bit message types and two 71-bit message subtypes are still TBD. NB: three 74-bit message types and two 71-bit message subtypes are still TBD.
---------------------------------------------------------------------------------- ----------------------------------------------------------------------------------
Facts about the 28-bit integers used to encode standard callsigns:
2^28 = 268,435,456 Available values
37*36*10*27*27*27 = 262,177,560 Needed for standard callsign structure
11*10*10*27*27*27 = 21,651,300 nnnaaa, _nnaaa (n=digit, a=letter or blank)
2^24 = 16,777,216 available for 24-bit hash code
4,874,084 available for special CQs, etc.
The 28-bit callsign field includes about 19 million impossible "calls" The 28-bit callsign field includes about 19 million impossible "calls"
that start with three digits. That's more than 2^24 = 17,777,216, so that start with three digits. That's more than 2^24 = 17,777,216, so
these values could be used to implement a 24-bit CRC -- in addition to the these values could be used to implement a 24-bit CRC -- in addition to the
@ -60,6 +71,7 @@ Further details:
4. One nonstandard call with up to 11 characters, one hashed call, 4. One nonstandard call with up to 11 characters, one hashed call,
followed by <blank>, RRR, RR73, or 73. followed by <blank>, RRR, RR73, or 73.
---------------------------------------------------------------------------
The following are tentative, not to be included in first release: The following are tentative, not to be included in first release:
5. CQ WW RTTY - US/Can: RST CQZ state/prov R 579 5 NJ R1 r3 z6 u7 5. CQ WW RTTY - US/Can: RST CQZ state/prov R 579 5 NJ R1 r3 z6 u7