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Editing the jtms3.txt file.

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git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/jtms3@2487 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Joe Taylor 2012-07-04 21:30:56 +00:00
parent 0718154e8b
commit a82d3eb454
3 changed files with 12 additions and 21 deletions
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30
jtms3.txt
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@ -5,32 +5,22 @@
Type 1 messages are 72 user-information bits, source encoded as in
JT65. Convolutional FEC (K=32, r=1/2) increases the number of bits to
(72+31)*2 = 206. Nine bits are sent twice, extending the array to 215
(72+31)*2 = 206; nine bits are sent twice, extending the array to 215
bits. These are interleaved by bit-reversal of index values. Then 43
sync bits are inserted, spread evenly so as to fall at positions 1, 7,
13, ... 253. Frame size is 258 bits: 215 information-carrying bits
and 43 sync bits. Frame duration is 129 ms.
[Optional: Type 2 messages convey 4 user information bits (report,
R+report, RRR, 73) encoded with a (15,4,8) block code, plus a 12-bit
CRC for each callsign encoded with the Golay (23,12) code. This
makes for 15 + 2*23 = 61 information-carrying bits. One dummy bit is
added, and the 62 bits are interspersed with 31 sync bits, making a
frams of 93 bits and frame time 46.5 ms.]
Type 2 messages convey 4 user information bits (report, R+report, RRR,
73) encoded with a (15,4,8) block code, plus a 12-bit CRC for each
callsign, encoded with the Golay (23,12) code. This makes for 15 +
2*23 = 61 information-carrying bits. One dummy bit is added, and the
62 bits are interspersed with 31 sync bits, making a frame of 93 bits
and frame time 46.5 ms.
2. Modulation is BPSK at 2000 baud. For sample rate 48000 Hz, this
means nsps = 48000/2000 = 24 samples per symbol. The baseband
waveform is built as follows:
a. Replicate each bit nsps times into array y(npts=30*48000),
substituting -1 for 0. Repeat the whole message enough times
to fill npts, then pad with zeros to length 2*npts.
b. Compute real-to-complex FFT of y(2*nsym*nsps). Roll off the complex
spectrum at f=1000 Hz. Translate the half-band 0-1000 upward to
1500-2500 Hz, and insert conjugate values at 1500 down to 500 Hz.
c. The inverse (complex-to-real) FFT yields the Tx audio waveform.
2. Modulation is BPSK at 2000 baud, 24 samples per symbol at 48000 Hz
asmple rate. The baseband waveform is built by inserting a tapered
sinc function for each bit, then multiplying by a 1500 Hz sine wave.
3. Receiving

1
libm65/genjtms3.f90
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@ -20,6 +20,7 @@ subroutine genjtms3(msg,msgsent,iwave,nwave)
call scr258(isync,datsym,1,chansym) !Insert sync and data into chansym(258)
if(msg(1:1).eq.'@') chansym=0
twopi=8.0*atan(1.0)
f0=1500.0
dphi=twopi*f0/48000.0

2
mainwindow.cpp
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@ -1,4 +1,4 @@
//-------------------------------------------------------------- MainWindow
//--------------------------------------------------------------- MainWindow
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "devsetup.h"