+ * http://www.ntia.doc.gov/files/ntia/publications/84-168.pdf
+ *
+ * Necessary bandwidth for a FSK modulated signal:
+ *
+ * bw = 2.6d + 0.55b 1.5 < m < 5.5
+ * bw = 2.1d + 1.9b 5.5 < m < 20
+ *
+ * b is the modulation rate in bps
+ * d is the peak deviation (from the center)
+ *
+ * m = 2d / b
+ *
+ * 20.5 kHz deviation 38.4kbps signal:
+ *
+ * m = 41 / 38.4, which is < 5.5:
+ *
+ * bw = 2.6 * 20.5 + 0.55 * 38.4 = 74.42kHz
+ *
+ * M = 1, E = 3, bw = 75kHz
+ *
+ * 5.125 kHz deviation, 9.6kbps signal
+ *
+ * m = 10.25 / 9.6, which is < 5.5:
+ *
+ * bw = 2.6 * 5.125 + 0.55 * 9.6 = 18.6kHz
+ *
+ * M = 2, E = 3, bw = 53.6kHz
+ *
+ * 1.28125kHz deviation, 2.4kbps signal
+ *
+ * m = 2.565 / 2.4, which is < 5.5:
+ *
+ * bw = 2.6 * 20.5 + 1.9 * 2.4 = 47.61kHz
+ *
+ * M = 3, E = 3, bw = 53.6kHz
+ *