A word about the -symbollength flag:

symbollength sets the symbol length in samples. Defaults to 72.

Sample rate is determined by this value as follows:

DataRate = 32768
SampleRate = SymbolLength * DataRate

Sample rates are limited by the dongle such that:

225 kHz < Sample Rate < 300 kHz and
900 kHz < Sample Rate < 3.2 MHz

The symbol length along with the message type determines the size of sample blocks read and processed on each pass.

PreambleSymbols = 21 (for SCM) and 32 (for IDM)

BlockSize = NextPowerOf2(d.Cfg.PreambleLength)

func NextPowerOf2(v int) int {
	return 1 << uint(math.Ceil(math.Log2(float64(v))))
}

Valid symbol lengths are given below, with a block size calculated for SCM:

Symbol Length	Sample Rate	Block Size	Symbol Length	Sample Rate	Block Size
28	917.504 kHz	2048	39	1.277952 MHz	2048
29	950.272 kHz	2048	40	1.310720 MHz	2048
30	983.040 kHz	2048	41	1.343488 MHz	2048
31	1.015808 MHz	2048	42	1.376256 MHz	2048
32	1.048576 MHz	2048	43	1.409024 MHz	2048
33	1.081344 MHz	2048	44	1.441792 MHz	2048
34	1.114112 MHz	2048	45	1.474560 MHz	2048
35	1.146880 MHz	2048	46	1.507328 MHz	2048
36	1.179648 MHz	2048	47	1.540096 MHz	2048
37	1.212416 MHz	2048	48	1.572864 MHz	2048
38	1.245184 MHz	2048

Symbol Length	Sample Rate	Block Size	Symbol Length	Sample Rate	Block Size
49	1.605632 MHz	4096	74	2.424832 MHz	4096
50	1.638400 MHz	4096	75	2.457600 MHz	4096
51	1.671168 MHz	4096	76	2.490368 MHz	4096
52	1.703936 MHz	4096	77	2.523136 MHz	4096
53	1.736704 MHz	4096	78	2.555904 MHz	4096
54	1.769472 MHz	4096	79	2.588672 MHz	4096
55	1.802240 MHz	4096	80	2.621440 MHz	4096
56	1.835008 MHz	4096	81	2.654208 MHz	4096
57	1.867776 MHz	4096	82	2.686976 MHz	4096
58	1.900544 MHz	4096	83	2.719744 MHz	4096
59	1.933312 MHz	4096	84	2.752512 MHz	4096
60	1.966080 MHz	4096	85	2.785280 MHz	4096
61	1.998848 MHz	4096	86	2.818048 MHz	4096
62	2.031616 MHz	4096	87	2.850816 MHz	4096
63	2.064384 MHz	4096	88	2.883584 MHz	4096
64	2.097152 MHz	4096	89	2.916352 MHz	4096
65	2.129920 MHz	4096	90	2.949120 MHz	4096
66	2.162688 MHz	4096	91	2.981888 MHz	4096
67	2.195456 MHz	4096	92	3.014656 MHz	4096
68	2.228224 MHz	4096	93	3.047424 MHz	4096
69	2.260992 MHz	4096	94	3.080192 MHz	4096
70	2.293760 MHz	4096	95	3.112960 MHz	4096
71	2.326528 MHz	4096	96	3.145728 MHz	4096
72	2.359296 MHz	4096	97	3.178496 MHz	4096
73	2.392064 MHz	4096

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