Analog mode operation

README.md

@@ -34,3 +34,17 @@ cycle.
 You could of course also take either of the sine wave outputs (ZOUT1, ZOUT2)
 and amplify or feed directly into a low-pass filter to the antenna.
 
+## make_table.py and make_sound.py
+
+Code to support completely analog operation. Run `make_table.py` and write
+down the printed table on a piece of paper, making sure to include the
+horizontal lines after every 9th symbol. I simply fill the indicated
+squares with a pencil, and the whole message takes three columns on a piece of
+A4 graph paper.
+
+Then run `make_sound.py`, which creates the file `ticks.wav`. This file can be
+played (by an analog tape player, perhaps?) starting at an even minute. You
+should have no problem following the beat when keying the message, but if you
+lose track at some point, the higher tone at the symbol *before* each 9-symbol
+block boundary can be used for synchronization.
+

make_sound.py

@@ -0,0 +1,31 @@
+import numpy as np
+import math
+import scipy
+
+symbol_time = 8192/12000
+sr = 22050
+
+tick_hz = 450
+tack_hz = 700
+start_pad = 1.0
+end_pad = 1.0
+total_time = 162*symbol_time + start_pad + end_pad
+n_samples = int(total_time*sr)
+
+samples = np.zeros(n_samples, dtype=np.uint8)
+
+def add_sound_at(start_time, frequency, length=0.1):
+    start_sample = int(start_time*sr)
+    for i in range(int(length*sr)):
+        samples[start_sample+i] = 128 + int(64*math.sin(2*math.pi*i*frequency/sr))
+
+def main():
+    for i in range(162):
+        frequency = tack_hz if (i+1) % 9 == 0 else tick_hz
+        add_sound_at(start_pad + i*symbol_time, frequency)
+    add_sound_at(0.0, 1000.0, length=start_pad)
+
+    #print(list(samples))
+    scipy.io.wavfile.write("ticks.wav", sr, samples)
+
+main()

make_table.py

@@ -0,0 +1,25 @@
+"""Display for manual WSPR transmission."""
+
+from encode import wspr_encode
+
+import datetime
+import time
+
+def display(symbols):
+    for i, symbol in enumerate(symbols):
+        if i % 9 == 0:
+            print(f'-- {i:3d} ' + '-'*72)
+        left = ' ' if symbol & 1 else '#'
+        right = ' ' if symbol & 2 else '#'
+        print(f'[{left}] [{right}]')
+
+if __name__ == '__main__':
+    import sys
+    if len(sys.argv) != 4:
+        print('Usage: %s callsign locator dbm' % sys.argv[0])
+        sys.exit(1)
+    callsign = sys.argv[1]
+    locator = sys.argv[2]
+    dbm = int(sys.argv[3])
+    symbols = wspr_encode(callsign, locator, dbm)
+    display(symbols)