As mentioned above, the digital data that the telemetry system generates is converted to an analog signal using Frequency Shift Keying (FSK). FSK is a special type of modulation where the digital signals (``0" & ``1") changes the frequency of the pseudo carrier to one of two frequencies, usually denoted as MARK and SPACE respectively.
If is the duration of a bit, then the bandwidth (BW) occupied
by the FSK signal is:
For example, in the Forward Link,
MHz and microseconds (i.e. corresponding
to a data rate of 250 kbps). Therefore, the bandwidth of the FSK signal
in the forward link is