Axcera DT325B, Инструкция по эксплуатации

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350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-8
which are connected to J1, J2 and J3 on
(A4-A1) a 3 Way Combiner Board (1198-
1626).
4.2.7 (A5-A1) 3 Way Combiner
Board (1198-1626; Appendix D)
The 3 Way Combiner takes the three
+51.3 dBm combined inputs and
combines them to form the
approximately 375 Watt (+55.8 dBm) RF
Output at J4 of the Combiner which
connects to J2, the RF Output Jack of the
Tray.
The 3 Way Combiner Board provides a
Forward Power Sample at J5 and a
Reflected Output Power Sample at J8.
The Forward Output Power Sample
connects through the (A4-A2) low pass
filter board to J4 on (A5) the AGC Control
Board. The Reflected Output Power
Sample connects through the (A4-A3)
low pass filter board to J5 on (A5) the
AGC Control Board.
4.2.8 (A5) AGC Control Board
(1306482; Appendix D)
The AGC Control Board contains two
peak detector networks one for forward
and one for reflected power samples.
The forward power sample connects
through J4 to a detector circuit consisting
of CR11 and U3C. The detected forward
level is connected through R44 the
Forward Power metering level
adjustment which controls the gain of the
amplifier U3D. The forward peak
detected sample output of U3D is split
with one output connected to J7-4 which
is wired to the front panel meter for
monitoring purposes. Another output of
U3D connects to the IC U6 and related
components which comprise the module
fault circuit. The front panel mounted
module fault LED DS3, connected to J9-4
& 6, will light if the forward output power
drops below a preset level. The final of
the split outputs of U3D connects to the
IC U3A and related components which
comprise the AGC circuit. This level is
combined with the AGC reference inputs
at J2 and J6-2 which produces the AGC
output at J1 which connects to the
automatic level control circuit on the
Filter/Amplifier Board for the output
power of the tray.
The reflected power sample connects
through J5 to a detector circuit consisting
of CR13 and U5B. The detected reflected
level is connected through R53 the
Reflected Power metering level
adjustment which controls the gain of the
amplifier U5D. The reflected peak
detected sample output of U5D is split
with one output connected to J12-8
which is wired to the front panel meter
for monitoring purposes. The other
output of U5D connects to the IC U5C
and related components which comprise
the VSWR Cutback circuit. The front
panel mounted VSWR Cutback fault LED
DS4, connected to J12-2 & 1, will light if
the reflected output power increases
above the preset level set by R59.
Another output of U5C is detected by
CR15 and connected to the IC U3A and
related components which comprise the
AGC circuit. This level is combined with
the AGC reference inputs from the
forward power sample and at J2 and J6-2
which produces the AGC output at J1.
This output connects to the automatic
level control circuit on the Filter/Amplifier
Board that controls the output power
level of the tray.
Two voltages are applied to the rest of
the VHF amplifier tray when the enable is
connected to the tray. The voltages are
+28 VDC from the internal switching
power supply and +12 VDC from the
current metering board that connects to
J8-2 on the board where it is regulated
by U7 and connected to the rest of the
board.
The +12 VDC from the Driver/Amplifier is
connected to J3-7 & 8 on the rear of the
Tray that is wired to J8 Pin 4 & 1 on (A5)
the AGC Control Board. The +12 VDC is
connected to U8 a +5 VDC Regulator IC,
which supplies the +5 VDC needed for
operation of the front panel mounted