Assembly Instructions Chapter 4

4-6 kW UHF Translator Chapter 4, Circuit Descriptions
837B, Rev. 0 4-43
4.7.12 (A6) Dual Peak Detector
Enclosure (1227-1317; Appendix
D)
The dual peak detector enclosure
provides EMI and RFI protection for the
dual peak detector board, single supply
(1227-1333), which is mounted inside
the enclosure. The enclosure has two
inputs: a forward power sample at SMA
jack J1 and a reflected power sample at
SMA jack J2. The module has two
peak-detected sample outputs: a
forward power sample at FL2 from J4-4
on the board and a reflected power
sample at FL3 from J4-2 on the board.
The module also has a forward power
sample output at SMA jack J3 that
connects to a BNC jack J5 located on
the front panel.
The voltage, +32 VDC from the
amplifier protection board, connects to
FL1 on the assembly, which is wired to
J4-7 on the board.
4.7.13 (A6-A1) Dual Peak Detector
Board, Single Supply (1227-1333;
Appendix D)
The function of the dual peak detector
board is to detect forward and reflected
samples of visual or aural RF signals
and generate an output voltage
proportional to the power levels of the
sampled signals for metering purposes.
There are two identical signal paths on
the board: one for forward power and
one for reflected power. A sample of
forward output power, from the 4 way
combiner, enters the board at SMA jack
J1. Resistors R1, R2, and R3 form an
input impedance-matching network of
50Ω. The forward power signal is
detected by CR1, R4, R5, R7, R10, C1,
and C2. The output is buffered by
operational amplifiers U3B and U1C
before it is connected to forward power
output jack J4-4. U3 has a very high
input impedance that makes the IC less
sensitive to changes in the video level.
A sample of the forward power is
tapped off by R6 and R8 and fed to J3,
the forward sample output jack. Diode
CR2 provides temperature
compensation for diode CR1. An input
signal level of approximately +17 dBm
is enough to give a 1-VDC level at the
output of U1C.
A reflected output power sample, from
the 4 way combiner, enters the board
at SMA jack J2. Resistors R18, R19,
and R20 form an input impedance-
matching network of 50Ω. The reflected
power signal is then detected by CR3,
R21, R22, R24, C5, and C6 and the
output is buffered by operational
amplifiers U3A and U1B before it is
connected to reflected power output
jack J4-2. U3 has a very high input
impedance that makes the IC less
sensitive to changes in the video level.
Diode CR4 provides temperature
compensation for diode CR3. An input
signal level of approximately +17 dBm
is enough to give a 1-VDC level at the
output of U1B.
The +12 VDC needed for the operation
of U1 on the board is generated from
the +32 VDC that enters at J4, pin 7.
The +32 VDC is fed to U2, a voltage
regulator IC that produces +12 VDC at
its output, which is connected to U1.
4.7.14 (A7) Amplifier Protection
Board (1207117; Appendix D)
The amplifier protection board
distributes the biasing voltages to the
transistor amplifier devices that are
mounted on the amplifier boards in the
UHF amplifier tray. It also protects the
LDMOS devices on (A5-A2 to A5-A5)
the output amplifier modules from
overcurrent conditions using the board-
mounted 15-amp fuses F3 to F6. F1 is
board-mounted 10-amp fuse that
protects the LDMOS devices on (A4-A1)
the 40 Watt amplifier assembly and
also the transistor mounted on A3-A1
the 1 Watt amplifier board from
overcurrent conditions. F9 is a 3-amp
board-mounted fuse that protects the
+32 VDC that is applied to the amplifier