TM 11-5820-803-12
Figure 2-3. Random data modulation spectrum.
whenever one or more faults occur. This relay is shown
output power level of +10 dBm. Since the transmitter
in figure 2-1 in the no-fault (restored) condition. The
operates at the same frequency as the receiver, the
contact closure (short circuit during a fault condition) is
modem location, interface cabling, patching facilities, and
available between two pins at rear panel site interface
cable routing should all be chosen to provide maximum
connector J5. The fault alarm monitor output is used in
isolation between input and output. For best results, the
conjunction with a compatible remote monitoring device.
PSK modem should be located near the earth terminal
Connection of this signal is optional dependent upon the
up/ downconverters. The 70 MHz interfaces should be
configuration and operation requirements of the site.
connected via shielded 50-ohm RF cables. Cable
lengths and intermediate patching devices should be
minimized. In any installation, the following items should
2-3. Earth Terminal Interface Consideration.
be considered, although items in e and f below should
not present serious problems if the above guidelines are
Several factors which may degrade the earth terminal
followed:
interface signals have been discussed in the preceding
paragraph. An additional factor to consider is signal
a. If the upconverter maximum input power
leakage from the 70 MHz transmitter output to the 70
specification is less than the +10 dBm output power level
MHz receiver input. The receiver is capable of accepting
supplied by the PSK modem transmitter, an appropriate
signals at power levels as small as 85 dB less than the
attenuator should be added to the system.
transmitter
Table 2-1. Selection of Internal Transmitter Filter
INPUT DATA RATE
switch setting
TRANSMIT ERROR CODING switch setting
3 dB bandwidth of transmit filter
From 19.200 KB/S to 999.99 KB/S
NONE
3 MHz
From 19.200 KB/S to 499.99 KB/S
INTERNAL or EXTERNAL
3 MHz
From 1.0000 MB/S to 3.9999 MB/S
NONE
12 MHz
From 500.00 KB/S to 1.9999 MB/S
INTERNAL or EXTERNAL
12 MHz
From 4.0000 MB/S to 9.9999 MB/S
NONE
No filter
From 2.0000 MB/S to 5.0000 MB/S
INTERNAL or EXTERNAL
No filter
2-3
