From b40da9da923836a0823c4caef18d0f05fd8b4374 Mon Sep 17 00:00:00 2001 From: Bill Somerville Date: Thu, 10 Aug 2017 18:07:53 +0000 Subject: [PATCH] Fix FT8 encoding description git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@8021 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 --- doc/user_guide/en/protocols.adoc | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/doc/user_guide/en/protocols.adoc b/doc/user_guide/en/protocols.adoc index 3ccf00ec9..b302aa34a 100644 --- a/doc/user_guide/en/protocols.adoc +++ b/doc/user_guide/en/protocols.adoc @@ -61,15 +61,15 @@ _WSJT-X_ modes have continuous phase and constant envelope. [[FT8PRO]] ==== FT8 -Forward error correction (FEC) in FT8 uses a low-density -parity check (LDPC) code with 75 information bits, a 12-bit cyclic -redundancy check (CRC), and 174 channel symbols. It is thus called an -LDPC (174,87) code. Synchronization uses 7×7 Costas arrays at the -beginning, middle, and end of each transmission. Modulation is 8-tone -frequency-shift keying (8-FSK) at 12000/1920 = 6.25 baud. Each +Forward error correction (FEC) in FT8 uses a low-density parity check +(LDPC) code with 75 information bits, a 12-bit cyclic redundancy check +(CRC), and 87 parity bits making a 174-bit codeword. It is thus +called an LDPC (174,87) code. Synchronization uses 7×7 Costas arrays +at the beginning, middle, and end of each transmission. Modulation is +8-tone frequency-shift keying (8-FSK) at 12000/1920 = 6.25 baud. Each transmitted symbol carries three bits, so the total number of channel -symbols is 174/3 + 21 = 79. The total occupied bandwidth is -8 × 6.25 = 50 Hz. +symbols is 174/3 + 21 = 79. The total occupied bandwidth is 8 × 6.25 += 50 Hz. [[JT4PRO]] ==== JT4