• Based on wsprd and wsprcode source taken from WSJT-X 2.7.1
• wsprsimwav derived from wsprsim
• Code of CUI interface for WSPR TX/RX is at wspr-trx/

• Linux or macOS
• GNU Fortran for compiling WSJT-X code
  • See the latest WSJT-X source code from WSJT-X Web Page for how to build the code in details
• Advanced Python Scheduler

cd wsprd
make clean && make

• clang-format for C code
• fprettify for Fortran code

Use make format to format the code.

Note: tips for only WSPR-2 minute protocol are described unless otherwise noted

• Use wsprsimwav for generating a 48kHz mono WAV file, directly usable for transmission over USB transmitter
• The first and last 20 milliseconds parts of the sound generated by wsprsimwav are faded in/out with the raised-cosine envelope to reduce spurious emission

• WAV header (first 22 bytes) are ignored
• Format: fixed to S16_LE, 12000Hz, monaural (1 channel)
• Length: 114 seconds (see readwavfile() in wsprd.c)

• Length per file: 360026 bytes
• Header: 26 bytes
  • Filename: first 14 bytes as char
  • WSPR type: next 4 bytes as int (2 for WSPR-2, 15 for WSPR-15)
  • Frequency: next 8 bytes as double in MHz
• Interleaved IQ signal
  • Strictly 45000 frames for 120 seconds of 375 frames/second
  • each frame has two float numbers (4 x 2 = 8 bytes / frame)
  • frame data: I, and -Q (negated Q)

• wsprsim generates no noise if SNR is 40 or more
• wsprsim generates reverse shift signal of -f option when processed with the following csdr script

• Note: this sound output does not decode on WSJT-X
• Do not use this output for sending WSPR on the air

# upsample from 375Hz to 12000Hz sampling rate (with +-120Hz LPF)
# then shifting up 1500Hz (for make the signal audible)
# Output level: -6dB rms 
tail -c +27 201223_0000.c2 | 
    csdr plain_interpolate_cc 32 | 
    csdr bandpass_fir_fft_cc -0.01 0.01 0.001 | 
    csdr gain_ff 16 | csdr shift_math_cc 0.125 | 
    play --buffer=1024 -t raw -e floating-point -b32 -r 12000 -c 2 -q -

• The channel symbol output corresponds to lowest to highest frequencies, from 0 to 3, with 1.46484375 (= 12000/8192) Hz frequency shift, respectively.
• The channel spacing diagram from the center frequency:
  • Symbol 0: -2.197265625 Hz ( = -18000/8192 Hz)
  • Symbol 1: -0.732421875 Hz ( = -6000/8192 Hz)
  • Symbol 2: +0.732421875 Hz ( = +6000/8192 Hz)
  • Symbol 3: +2.197265625 Hz ( = +18000/8192 Hz)
• Transmission rate: 1.46484375 baud = 0.682666667 second/symbol = 8192/12000 second
• Each transmission contains 162 symbols for 110.592 seconds
• Each transmission starts +1 second after even UTC minute (e.g., 00:01, 02:01)

GPLv3