Comtech EF Data MM200 - Manual (Page 38)

User Interfaces MM200 High-Speed Microwave Modem
4-14 TM086 - Rev. 4.1
Screen Name Selections and Descriptions L0 L1 L2
FREQUENCY (Hz) {50 – 90 MHz}
Displays the current center band of the
operating frequency width. RW RW RW
CHANNELS {Auto, 1 - 4}
Controls the number of channel cards
where 0 = auto, and 1 – 4 = the number
of cards. Increase this number for better
performance. Lower this number for
better bandwidth efficiency. RW RW RW
SEPARATION {100% - 150%}
Selects the IF Frequency Separation in
percent, which is the additional
bandwidth percentage that the carrier will
cover over the original symbol rate. RW RW
DATA RATE (BPS) {7 – 200 Mbps}
Controls the total Data Rate. RO
SYMB RATE (SPS) {3.5 – 28 Msps}
Controls the total Symbol Rate. RW RW RO
DEMODULATION {QAM4, QAM16, QAM32, QAM64,
QAM128, QAM256}
Displays the current Demodulation
Scheme. RW RW RO
BANDWIDTH (Hz) Displays the frequency difference
between the highest channel’s upper 3-
dB point and the lowest channel’s lower
3-dB point. RO RO RW
UTILIZATION (%) Displays the percentage of the data
being transferred that is being used by
the selected interfaces. Must be less
than 100%. Maximize this number for
best bandwidth efficiency by lowering the
symbol rate, QAM Mode, or the number
of channels. RO RO RO
MAX PAYLOAD (Hz) Displays the maximum total data rate
that is useable for the current settings. RO RO RO
SPECTRUM {Normal, Inverted} RW RW RW
ATTENUATION {0 - 31}
Sets the Demodulator Input IF Attenuator
in 1 dB steps. RW RW RW
ACQUISITION (menu):
The Demodulator Acquisition Frequency
range can be set by the user. This is
required at higher QAM rates when using
radios with significant frequency drift. As
QAM rates increase, the ability of the
receiver to acquire to a signal that is
offset from the programmed demodulator
frequency is reduced. At QAM256 the
acquisition window can be as low as ± 50
kHz. Yet at QAM4, the window can be
over ± 1 MHz. This range can be further
reduced by noise or degraded receive
signals.
When trying to acquire a signal, the
MM200 follows this procedure: