Innovator CU10BT-CU5000BT Analog Transmitter
Board Descriptions
Instruction Manual, Rev. 0
51
Heatsink
Temperature
Sensor
RF Input
+10 dBm
RF Output
+46 dBm
+32 dBm
(A6) Amplifier Assembly (1309621) – Used in the CU5BT
The (A6) Amplifier Assembly (1309621) is made up of (A6-A1) the 2 Stage UHF
Amplifier Board, 24V (1309608). The assembly has approximately 33 dB of gain.
(A6-A1) 2 Stage UHF Amplifier Board, 24V (1309608)
The 2 Stage UHF Amplifier Board, 24V (1309608) consists of a driver stage with a gain
of +14dB and two parallel connected final amplifier stages each with a gain of +14dB.
The working point settings for the 2 Stage Amplifier Board are factory set using the
potentiometers R32 for Q2, R15 for Q1, and R24 for Q3 and should not be altered. The
input RF connects to the first amplifier stage Q2. The output is split by U2 and
connected to the final amps. The final amplification circuit consists of parallel-connected
push-pull LDMOS amplifier circuits Q1 and Q3 operating in class AB each with
approximately 14 dB of gain. The board uses a power supply voltage of 24V. The RF
transistors are operated at a voltage of 24V generated by the voltage regulators U6 and
U7 for Q2, U5 and U3 for Q3 and U1 and U3 for Q1, which provide a separate regulated
voltage to each transistor. In order to match the LDMOS impedance to the
characteristic impedance of the input and output sides, matching networks are located
before and after the amplifier circuits. The hybrid coupler U2 splits the input to the
parallel amplifiers and the hybrid coupler U4 combines the amplified outputs. The
combined output connects through a directional coupler to J1, the RF output jack of the
board. The directional coupler provides an RF sample at J3 that is used by an external
overdrive protection circuit located on (A5) the ALC Board. The RF output of the board
is 6W maximum 8-VSB. At this power level the board draws approximately 3.6A total
from the power supply.
Summary of Contents for Innovator CU10BT/CU0T-1
Page 72: ......