User's Manual

P.G. TM0051
2-1
SECTION 2. THEORY OF OPERATION
2.0 GENERAL
The R307B is a bidirectional repeater, providing a maximum of approximately 60 dB
gain in the SMR uplink and downlink bands. The block diagram of the R307B is
shown in Figure 2-1.
2.1 - The unit is composed of amplifiers and diplexers as well as voltage regulation
circuits. The downlink signal enters the unit via Base Antenna connector (the
common port of diplexer U2). The signal passes through the high band port of
diplexer U2 to drive amplifier 2. The output of amplifier 2 is fed into the high band
port of diplexer U1 and then is output at the Distribution Antenna connector.
2.2 - The unit's operation in the uplink band is similar to the downlink band
discussed in section 2.1 above but uses amplifier 1 and the low band ports of
diplexers 1 and 2 to provide gain from the Distribution Antenna to the Base
Antenna.
2.3 - The total current drawn by the uplink amplifier is approximately 450 mA.
Similarly, the total current for the downlink amplifier is 450 mA.
2.4 - The R307B Repeater requires external DC power to be supplied through its
DC power connector (center positive). An external AC-DC adapter is provided with
the unit.
2.5
- The unit contains a downlink power detection circuit which signals an alarm if
the unit is operated above its rated downlink output power level. If the downlink
output power rating is exceeded, the red "ALARM" LED on the bottom of the unit is
illuminated. The operator must then reduce the gain of the unit by increasing the
"DOWNLINK" attenuator setting such that the unit is operated within its downlink
power capability as specified in Table 1-2. Refer to Section 3: Installation,
Operating and Maintenance Instructions. (See NOTE in Section 3.3).
2.6 - The unit contains an uplink ALC circuit. This circuit prevents overloading of
the uplink amplifier due to excessive uplink signal levels into the "DISTRIBUTION"
port. (See NOTE in Section 3.3).