Comtech EF Data CDM-570/L Vipersat Parameter Editor - Manual (Page 65)

Chapter 2 - Using Parameter Editor 2-49
Vipersat
Demodulator Delay
This field allows the operator to insert additional delay to account for the tuning
of the demodulator.
Lock Times
Lock Time settings for the four data rates displayed can be adjusted either up or
down, but default settings based on satellite testing should be used as a starting
point. These defaults are stored in each modem unit and are restored by clicking
on the Defaults button.
The initial setting is with Hitless Switching disabled—all check boxes are
unchecked, and the lock times are displayed as -1 msec. Selecting the check box
for a data rate will activate the field for that rate, display the current lock time,
and allow that value to be edited.
DPC
The DPC dialog for a Hub or Remote operating in STDMA mode is displayed
in figure 2-33. Note that, for an Expansion unit, only the Speed Up Eb/N0 and
the Target IP Addresses fields are active.
Dynamic Power Control (DPC) is a Vipersat feature that acts to regulate the
transmit power of the Vipersat satellite modem, such that the specified receive
signal level (E
b
/N
0
) is met for the receiving Vipersat units in the group. DPC is
driven by the receiver demod, which notifies the transmitting modem of the
current E
b
/N
0
value.
Before enabling DPC, the operator should verify that a demodulator at another
terminal is receiving from this modulator, and that there is a working communi-
cations channel from that receiving station back to the modulator terminal
(InBand communications). Additionally, since DPC potentially controls the full
power range of the modulator’s output power, it is recommended that the termi-
nal be commissioned and calibrated before usage.
Warning: Make certain that all CDM-570/570L’s in the network have their
Automatic Uplink Power Control (AUPC) turned off. Although this
Comtech modem function is available for a connection between two
point-to-point units, it will conflict when used in a network using the
network-wide DPC. Using both in a circuit will produce erratic and
unstable operation with potential data loss, low QoS, and potential
loss of the circuit connection.