Bird Technologies Group 5PI613805 Manual De Usuario
TXRX Systems Inc. Manual 7-9408-1.2 07/25/05 Page 19
61-38-05 UserMan page 19 of 38
The bias regulator circuit uses an Op-Amp compar-
ator IC1 to supply a variable bias current which var-
ies as required to keep the RF transistors collector
current constant. Current to the collector of the RF
transistor flows through resistor R1. The voltage at
the collector side of this resistor is applied to the
non-inverting input of IC1. Voltage divider R2 / R4
sets the desired reference voltage on the inverting
terminal of IC1. The variable output voltage at pin 6
of IC1 is then applied to the base of the RF transis-
tor. The bias on the RF transistor will now vary in
such a way as to keep the voltage at the collector
end of R1 equal to the reference voltage provided
by divider R2/R4, thus keeping the RF transistor's
collector current constant (121 ma nominal).
Repair or replacement of bias circuit components
does not necessitate retuning of the amplifier.
ator IC1 to supply a variable bias current which var-
ies as required to keep the RF transistors collector
current constant. Current to the collector of the RF
transistor flows through resistor R1. The voltage at
the collector side of this resistor is applied to the
non-inverting input of IC1. Voltage divider R2 / R4
sets the desired reference voltage on the inverting
terminal of IC1. The variable output voltage at pin 6
of IC1 is then applied to the base of the RF transis-
tor. The bias on the RF transistor will now vary in
such a way as to keep the voltage at the collector
end of R1 equal to the reference voltage provided
by divider R2/R4, thus keeping the RF transistor's
collector current constant (121 ma nominal).
Repair or replacement of bias circuit components
does not necessitate retuning of the amplifier.
Driver Amplifier Stage (3-11423)
The remaining three stages of the amplifier assem-
bly 3-11423 are used to form a driver amplifier
which amplifies the passband signals to levels suf-
ficient for driving the input of the final High Power
Amplifier stage. Each of the three individual 400
milliwatt stages in the driver amp are identical and
were discussed in detail in the earlier sub-section
entitled "Pre-Amplifier (3-11423)".
The remaining three stages of the amplifier assem-
bly 3-11423 are used to form a driver amplifier
which amplifies the passband signals to levels suf-
ficient for driving the input of the final High Power
Amplifier stage. Each of the three individual 400
milliwatt stages in the driver amp are identical and
were discussed in detail in the earlier sub-section
entitled "Pre-Amplifier (3-11423)".
High Power Amplifier Assembly (3-11792)
This amplifier stage uses a single ultra-linear RF
transistor. The 3.0 watt rating indicates the maxi-
mum safe output from this amplifier assembly
using a single carrier. The actual maximum allow-
able power output with multiple carriers is much
lower and is determined by the maximum allowable
intermodulation product level. It is also limited by
the collector to emitter breakdown rating of the RF
transistor.
This amplifier stage uses a single ultra-linear RF
transistor. The 3.0 watt rating indicates the maxi-
mum safe output from this amplifier assembly
using a single carrier. The actual maximum allow-
able power output with multiple carriers is much
lower and is determined by the maximum allowable
intermodulation product level. It is also limited by
the collector to emitter breakdown rating of the RF
transistor.
This amplifier stage is physically mounted to the
inside of the heatsink located on the side of the
cabinet. The amplifier draws a nominal 420 ma. A
bias regulator circuit within the amplifier assembly
is used to keep the collector current of the RF tran-
sistor constant with changes in temperature. This
amplifier has a minimum gain of 18 dB, 19 dB typi-
cal. The amplifier uses narrow band matching tech-
niques and will require tuning if the transistor or
matching network components are replaced.
inside of the heatsink located on the side of the
cabinet. The amplifier draws a nominal 420 ma. A
bias regulator circuit within the amplifier assembly
is used to keep the collector current of the RF tran-
sistor constant with changes in temperature. This
amplifier has a minimum gain of 18 dB, 19 dB typi-
cal. The amplifier uses narrow band matching tech-
niques and will require tuning if the transistor or
matching network components are replaced.
Signal Sampler (3-6999)
Following the output of the power amplifier assem-
bly is a -25 dB signal sampler. This sampler is used
Following the output of the power amplifier assem-
bly is a -25 dB signal sampler. This sampler is used
to couple the output signal level back to the OLC
assembly.
assembly.
Signal Sampler (3-3569)
This sampler is located at the output of the uplink
and downlink branches and is used for connecting
test equipment to the branch, such as a spectrum
analyzer. The 3-3569 signal sampler capacitively
couples signals to the sample port at a -50 dB
level.
This sampler is located at the output of the uplink
and downlink branches and is used for connecting
test equipment to the branch, such as a spectrum
analyzer. The 3-3569 signal sampler capacitively
couples signals to the sample port at a -50 dB
level.
DC Junction Box (3-6254)
This assembly has no internal components and is
used to couple battery backup voltage (supplied by
the customer) to the power supply.
This assembly has no internal components and is
used to couple battery backup voltage (supplied by
the customer) to the power supply.
Power Supply Assembly (3-15503)
The power supply assembly consists of two sub-
assemblies, an OEM power supply module and a
failure switching circuit. The switching circuit is
designed to pass the output from either the OEM
power supply or the backup batteries to the TNC
style output connectors which are labeled “24.7
VDC Output” located on the assemblies front panel
next to the fuses.
The power supply assembly consists of two sub-
assemblies, an OEM power supply module and a
failure switching circuit. The switching circuit is
designed to pass the output from either the OEM
power supply or the backup batteries to the TNC
style output connectors which are labeled “24.7
VDC Output” located on the assemblies front panel
next to the fuses.
The output of the OEM supply (part# 8-15495) is
applied to the output TNC connectors through relay
K2 pins 9 and 10. The voltage feed is protected by
fuse F1 (10 amp). During normal operation relay
K2 is energized connecting pin 9 to pin 10. If AC
power is interrupted relay K2 becomes de-ener-
gized connecting pin 9 to pin 8 which is fed from
the battery backup. This will pass battery voltage to
the output TNC connectors.
applied to the output TNC connectors through relay
K2 pins 9 and 10. The voltage feed is protected by
fuse F1 (10 amp). During normal operation relay
K2 is energized connecting pin 9 to pin 10. If AC
power is interrupted relay K2 becomes de-ener-
gized connecting pin 9 to pin 8 which is fed from
the battery backup. This will pass battery voltage to
the output TNC connectors.
With AC voltage applied to relay K2 pin 6 will be
connected to pin 7 completing the ground path for
the green LED D2. When K2 is de energized indi-
cating AC power failure pin 5 is connected to pin 6
completing the ground path for the red LED D1
indicating the unit is operating on DC backup volt-
age.
connected to pin 7 completing the ground path for
the green LED D2. When K2 is de energized indi-
cating AC power failure pin 5 is connected to pin 6
completing the ground path for the red LED D1
indicating the unit is operating on DC backup volt-
age.
The Loss of AC Alarm Terminal block is provided
for customer convenience. Under normal system
operation, when the OEM supply voltage is active,
the NC terminal is shorted to the COM terminal
because pins 5 and 6 are connected by relay K1.
K1 is energized whenever the AC power supply is
active. When the system is running on battery
backup voltage the NO terminal is connected to the
COM terminal because pin 5 will now be con-
for customer convenience. Under normal system
operation, when the OEM supply voltage is active,
the NC terminal is shorted to the COM terminal
because pins 5 and 6 are connected by relay K1.
K1 is energized whenever the AC power supply is
active. When the system is running on battery
backup voltage the NO terminal is connected to the
COM terminal because pin 5 will now be con-