User's Manual

Innovator CU0TD-1/CU0RD-1 – CU4TD/CU4RD Board Descriptions
ATSC Transmitter/Regenerative Translator
Instruction Manual, Rev. 1 64
the +5VDC and ±12VDC outputs connect directly to the 8 VSB Demodulator and 8 VSB
Modulator boards while the other outputs connect through the CU Control Board to the
IF Precorrector, the Digital Upconverter, the ALC, the Amplifier Assembly and the Output
Detector Boards.
The +24/+28/+30/+42/+48VDC VDC outputs of the (A10) power supply connect to the
(A8) CU Control Board, which then supplies the switched +24/+28/+30/+42/+48VDC
VDC to the (A6) Amplifier Assembly. In CU0TD/RD-1 thru CU0TD/RD-3 drawers the DC
output of the (A10) power supply also connects to the (A11) fan mounted on the rear
panel, which will operate when AC is applied to the drawer, the On/Off circuit breaker is
On and the (A10) power supply is operating.
Circuit Description of External System Metering Board which is only used in
Transmitters with multiple external Amplifier Drawers
(A5) System Metering Board (1312666)
The function of the System Metering Board is to detect forward and reflected output power
samples and generate output voltages that are proportional to the power levels of the
sampled signals for use by the control monitoring assembly in the exciter/driver drawer.
There are two identical signal paths on the board: one for forward power and one for
reflected power. A sample of the forward output power, from the external (A11) output
coupler, enters the board at the SMA jack J3. The signal is filtered and connected to
resistors R5, R3 and R6 that form an input impedance-matching network to Pin 3 on U1.
The forward power signal is detected by the RF detector IC U1. The detected output at
pin 7 is split with one half connected to the forward average calibration pot R7, digital,
which adjusts the level of the signal connected to Pin 11 on U2. The other half of the split
is connected to the peak calibration pot R18, analog, which adjusts the level of the signal
connected to Pin 8 on U2. U2 is a Bilateral Switch IC whose output, digital or analog, is
controlled by the selection of the modulation type in the exciter/driver drawer. In this
BTC transmitter the average, digital, output connects to the amplifier IC U3A that is wired
to the SYS_FWD and RMT_FWD Power Metering Outputs. A reading of 2 VDC measured at
TP1 is equal to a 100% Forward Power reading on the meter. The SYS_FWD level
connects to J9 on the board that is cabled to J11 on the exciter/driver drawer for use in
the control monitoring assembly. The RMT_FWD level connects to J10 on the board for
use by remote control and monitoring.
A sample of the reflected output power, from the external (A11) output coupler, enters
the board at the SMA jack J8. The signal is filtered and connected to resistors R26, R22
and R27 that form an input impedance-matching network to Pin 3 on U6. The reflected
power signal is detected by the RF detector IC U6. The detected output at pin 7 is
connected to the reflected calibration pot R25, which adjusts the level of the signal
connected to the amplifier IC U3B that is wired to the SYS_RFLD and RMT_RFLD Power
Metering Outputs. A reading of 2 VDC measured at TP2 is equal to a 25% Reflected
Power reading on the meter. The SYS_RFLD level connects to J9 on the board that is
cabled to J11 on the exciter/driver drawer for use in the control monitoring assembly. The
RMT_RFLD level connects to J10 on the board for use by remote control and monitoring.
+12 VDC enters the board at J9-1, from the exciter/driver drawer and is connected
through a filter and isolation circuit consisting of C31, C14 and L5 before it is connected to
the regulator IC U5. U5 supplies the +5 VDC needed for operation of the ICs on the