mirror of https://github.com/saitohirga/WSJT-X.git
266 lines
11 KiB
Plaintext
Executable File
266 lines
11 KiB
Plaintext
Executable File
1 Introduction
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WSJT is a computer program designed to facilitate Amateur Radio
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communication under extreme weak-signal conditions. Three very
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different coding and modulation methods are provided: one for
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communication by "meteor scatter" techniques on the VHF bands; one for
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meteor and ionospheric scatter, primarily on the 6 meter band; and one
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for the very challenging EME (Earth-Moon-Earth) path.
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2 Program Overview
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WSJT's user interface is written in Python. The major Python
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source-code files include:
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1. wsjt.py Defines the main-screen GUI for user interactions;
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acts as "traffic cop" for orchestrating all
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event-driven and time-shared activities.
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2. specjt.py Provides real-time display of received signals as
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two-dimensional "waterfall" spectra.
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3. options.py Provides entry fields for user-defined parameters.
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4. astro.py Displays astronomical data for sun, moon, sky
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temperature, etc.
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Smaller Python files serve various utility purposes.
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Both wsjt.py and specjt.py make calls to external procedures compiled
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from Fortran and C. A variety of global data is shared among modules
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through common blocks defined in Fortran. The Python code runs in a
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single thread, although timers make the functions of the several main
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modules appear concurrent. Fortran routines create additional threads
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to be used for soundcard I/O and the decoding of received messages.
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As a small part of its overall task, the decoder for JT65 invokes an
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external program named KVASD.EXE or KVASD, located in the main
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WSJT directory. If this program is present it uses information on
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received 64-FSK symbols and attempts to decipher it according to a
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Reed Solomon (63,12) code, using the algebraic soft-decision algorithm
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of Koetter and Vardy. If KVASD is not present, WSJT uses its own
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internal hard-decision Reed Solomon decoder instead. Interprocess
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communication between WSJT and KVASD takes place through a shared disk
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file. KVASD is not an integral part of WSJT. Its algorithm is
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patented, and the source code is the property of CodeVector
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Technologies, LLC. However, compiled versions of KVASD may be freely
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used in conjunction with WSJT for the purposes of amateur radio
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weak-signal communication.
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3 Some Functional Details
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WSJT execution starts at the top of Python file wsjt.py. The
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other Python modules are loaded and executed as needed. Fortran
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routines are called to start a high-priority thread to handle
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continuous A/D and D/A streams, and a background thread to decode
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received or previously recorded signals. The top-level Python
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code determines the overall state of program operation, e.g.,
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Idle, Monitoring, or Transmitting. In normal usage the operator
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puts the program into Auto mode, resulting in a timed sequence of
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alternating transmission and reception intervals.
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4 Other Open-Source Software used in WSJT
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WSJT 5.9 uses the following open source libraries:
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1. FFTW, by Matteo Frigo and Steven Johnson, for computing Fourier
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transforms
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2. PortAudio, by Ross Bencina and Phil Burk, for audio I/O
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3. "Secret Rabbit Code" or "libsamplerate", by Erik de Castro, for
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accomplishing band-limited resampling of data
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4. RS, by Phil Karn, KA9Q, for Reed Solomon encoding and
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hard-decision decoding.
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5 Platform-Dependent Notes
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The Python code should run on any supported Python platform. Most of
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the remaining code can be recompiled for Linux or OS/X, instead of
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Windows. Platform-dependent versions of FFTW, PortAudio, and
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libsamplerate need to be installed.
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Methods are provided for creating additional threads and setting their
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runtime priorities in both Windows and Linux.
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6 Partial List of Functions and Subroutines, and their purposes
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Audio.f90 Routines for audio startup, decoding, display computations
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blanker.f90 Noise blanker
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fivehz.f90 Called by PortAudio callback
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flat2.f Flatten the spectrum for waterfall display
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pix2d65.f90 Computes pixels for waterfall display
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pix2d.f90 Computes pixels for waterfall display
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runqqq.f90 Executes another process
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wsjtgen.f90 Generates Tx waveforms
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abc441.f90 Part of FSK441 generator
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gen65.f Generate JT65 waveform
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chkmsg.f Check a JT65 message for presence of 'OOO'
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encode65.f Encode a JT65 message
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getpfx1.f Handle extra DXCC prefixes
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getpfx2.f ...
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graycode.f Convert binary to/from Gray code
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nchar.f Convert number, letter, space to 0-36
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packcall.f Routines for JT65 source encoding
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packdxcc.f ...
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packgrid.f ...
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packmsg.f ...
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packtext.f ...
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pfx.f ...
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gen6m.f Generate JT6M waveform
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gentone.f Generate tone for JT6M message
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gencw.f Generate CW waveform
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morse.f Convert ascii to morse dits
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gencwid.f Generate a CW ID message
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grid2k.f Convert grid locator to integer
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interleave63.f Interleave JT65 symbols
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gcom1.f90 Global commons for sharing data among Fortran routines
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gcom2.f90 and between Fortran and Python
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gcom3.f90
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gcom4.f90
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makedate.f90 Gererates makedate_sub.f90
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Astronomical calculations:
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astro.f Computes Az, El, Doppler for Sun, Moon, etc.
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astropak.f "Includes" for astro supoport routines
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azdist.f Computes azimuth, distance, etc., between two locators
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coord.f Spherical trig utility
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dcoord.f Spherical trig utility in double precision
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deg2grid.f Convert lat/long (degrees) to grid locator
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dot.f Compute dot product
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ftsky.f Get sky temperature from data file
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geocentric.f Convert geodetic to geocentric coords
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GeoDist.f Compute azimuth and distance between two locators
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grid2deg.f Convert grid locator to lat/long
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moon2.f Compute moon location at specified date and time
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MoonDop.f Compute lunar doppler shift and related quantities
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sun.f Compure sun location at specified date and time
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toxyz.f Convert between polar and cartesian coords
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Utilities:
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db.f Compute decibels from ratio
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gasdev.f Generate Gaussian random numbers
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igray.f Gray code
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indexx.f Sort routine
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set.f Move, add, zero, ...
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pctile.f Sort an array and get specified percentile
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ran1.f Uniform random numbers
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rfile2.f Read a binary file (Linux)
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sort.f Sort an array
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FFTs:
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fftw3.f Fortran definitions for FFTW
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four2a.f Wrapper to make FFTW look like four2
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four2.f FFT in Fortran
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ps.f Compute power spectrum
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xfft.f Real to complex FFT wrapper
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Routines for Decoding:
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wsjt1.f Top-level decoding routine; handles FSK441 especially
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avesp2.f Computes average spectrum
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bzap.f Find and remove birdies
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detect.f Measure power in FSK441 tones
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flatten.f Flatten the spectrum
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longx.f Decode normal FSK441 messages
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lpf1.f Quick-and-dirty lowpass filter
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mtdecode.f Multi-tone decoding
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ping.f Find pings
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s2shape.f Flatten the 2d spectrum
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smooth.f Smooth by boxcar averaging
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spec2d.f Compute 2d spectrum for FSK441
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stdecode.f Decode FSK441 shorthand messages
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sync.f Synchronize FSK441 data
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wsjt65.f JT65 decoder
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afc65.f AFC for JT65
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avemsg65.f Decode average message
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decode65.f Decode JT65 message
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deep65.f Deep search decoder
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demod64a.f Compute probabilities of transmitted symbols
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extract.f Extract message from JT65 symbol probabilities
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flat1.f Flatten the passband
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getsnr.f Compute snr or shorthand message
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k2grid.f Convert integer to 4-digit grid locator
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limit.f Clipper for JT65
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peakup.f Interpolate to find fractional-bin peak
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setup65.f Initialize pseudorandom sync vector
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short65.f Detect JT65 shorthand messages
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slope.f Remove a straight-line slope
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spec2d65.f Compute 2d spectrum for JT65
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spec441.f Compute spectra for FSK441 decoding
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sync65.f Synchronize a JT65 signal
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unpackcall.f Unpack JT65 message parts ...
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unpackgrid.f ...
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unpackmsg.f ...
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unpacktext.f ...
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xcor.f Compute cross-correlation for JT65 sync
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decode6m.f Decode JT65 signal
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syncf0.f First frequency sync
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syncf1.f Second freq sync
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synct.f First time sync
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avemsg6m.f Get average JT65 message
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JT65code.f Program to illustrate and test JT65 coding
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Hard-Decision Reed Solomon Codec
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decode_rs.c Decoder
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encode_rs.c Encoder
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init_rs.c Initialization routine
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wrapkarn.c Wapper for Fortran
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cutil.c Fortran wrappers for some basic C functions
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jtaudio.c Audio I/O, calls PortAudio routines
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padevsub.c Select desired audio device
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ptt.c PTT via serial port DTR/RTS
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ptt_linux.c Ditto for Linux (dummy at present)
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resample.c Wrapper for resample routine
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start_threads.c Start audio and decoder threads
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7 Compiling Instructions
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Scripts are provided for compiling WSJT in both Windows and Linux.
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They are presently set up to use Compaq Visual Fortran (v6.6) and
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Microsoft C (v6.0) in Windows, and g95 and gcc in Linux. My
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installation has Python 2.3. Additional tools include f2py, which
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compiles Fortran and C to make Python extensions; the Python Imaging
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Library; Numeric Python; and the SciPy distribution utilities.
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Linux Windows Function
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-------------------------------------------------------------------
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g0 g0.bat Compiles the hard-decision Reed Solomon Decoder
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Needs to be done only once.
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g1 g1.bat Compiles the remaining Fortran and C to produce Python
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extension module audio.pyd (Windows) or audio.so
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(Linux).
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g2.bat Uses McMillan Installer to create an f2py specification
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file, wsjt.spec
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g3.bat Uses Installer to produce a distributable file WSJT6.EXE
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(Windows).
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The final two build steps have not yet been tried in Linux. In Windows,
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these steps produce a distributable file WSJT6.EXE that contains all
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necessary software components, so that the user does not need to install
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Python or any of its other extensions.
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8 Present status (December 20, 2005)
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WSJT version 5-9-2d is fully functional in Windows. The Linux version
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can be used to decoded recorded files, but real-time audio I/O has not
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yet been implemented.
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