Comtech EF Data DMDVR20 LBST Rev 1.1 - Manual (Page 47)

User Interfaces DMDVR20 LBST Satellite Modem
4-10 TM136 – Rev. 1.1
IF (menu)
FREQUENCY (MHz) {950 – 2150 MHz}
Allows the user to enter the Modulator IF Frequency in 1
Hz increments.
DWNLNK FREQ (MHz)
Displays the input frequency into the LNB from the
satellite, also referred known as Satellite downlink
frequency. The user must enter the LNB LO and OSC
SIDEBAND of the LNB before using this menu. The
DOWNLINK FREQUENCY is a calculated measurement
of both the LNB LO and OSC SIDE BAND. Once the
menus are entered correctly, the user can control the
downlink Frequency from this menu.
SPECTRUM {NORMAL, INVERTED}
Allows the user to invert the direction of rotation for PSK
Modulation. Normal meets the IESS Specification.
Spectral inversion may be required if the LNB LO is
higher in frequency than the LNB input frequency from
the satellite. When LNB LO is higher in frequency than
the LNB input frequency, this creates a spectral
inversion and the IF Spectrum must be inverted to
compensate for the inversion.
MODULATION {QPSK, 8PSK, 16APSK}
Allows the user to select the demodulation type.
SPECTRAL MASK
{DSS 0.35, DSS 0.25, DSS 0.20}
Allows the user to set the spectral shape of Rx Data
Filter.
SWEEP RANGE (kHz) {+/- 0.10 * Symbol Rate up to 7.5 MHz}
Allows the user to set the acquisition range for the
demodulator
INPUT LVL THRESH {-30 to 90 dbm}
Allows the user to adjust the low level threshold limit for
input power. Input power level below the threshold limit
will trigger a major alarm on the demodulator.
EB/NO ALARM {0.0 to 9.90 db}
Allows the user to set the desired E
b
/N
o
for the local
receiver. This setting is compared against the receive
E
b
/N
o
and commands to the remote modem to increase
or decrease Transmit Power accordingly are sent.