Buffer Setup - Comtech EF Data SDM-650B Installation And Operation Manual

Configuration

3.3.1 Buffer Setup

The receive buffer allows for:
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If two earth stations are configured as a master/slave unit, then the buffer need only be
configured for Doppler operation. The buffer has sufficient capacity for the Doppler shift
on the outward and return paths.
A buffer setup for the Doppler operation will typically require less depth than one
intended for both Doppler and plesiochronous operations.
3–44
Plesiochronous buffering of two dissimilar clock frequencies: the far end transmit
clock and the local network clock frequency. The clocks may be very close in
frequency to each other and will normally slip at a constant rate. Figure 3-15
shows plesiochronous operation of dissimilar clocks. If incoming traffic is too
fast, an occasional bit will be lost. If incoming traffic is too slow, an occasional
bit will be repeated.
Doppler buffering of the signal from the satellite. A Doppler shift results from
the satellite's figure 8 shaped orbit over a period of one day. A Doppler shift
should not result in a clock slip; the buffer constantly fills and empties.
SDM-650B Satellite Modem
Rev. 5