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WSPR CUI code

  • 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/

Requirements

How to build

cd wsprd
make clean && make

Code formatting

Use make format to format the code.

Tips

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

For generating wav file

  • 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

For reading wav file by wsprd

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

.c2 file format by wsprd

  • 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)

For generating .c2 file

  • 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

Make .c2 file audible

  • 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 -

WSPR-2 timing and frequency

  • 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)

LICENSE

GPLv3