User's Manual

350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-3
of the transmitter’s power amplifier are
routed to the system power monitoring
lines.
4.1.2.2 Schematic Sheet 2
Digital output latch circuits are used to
control system devices. Remote output
circuits are implemented using open
drain FETs, Q13, Q14, Q16, and Q17,
with greater than 60 Volt drain to source
voltage ratings.
Remote digital inputs are diode
protected, using CR6, CR7, CR8 and CR9
with a 1 kO pull-up resistor, to +5 VDC.
If the remote input voltage is greater
than about 2 Volts or floating, the FET is
turned on and a logic low is applied to
the digital input buffer, U9. If the
remote input voltage is less than the
turn on threshold of the FET (about 2
VDC), a logic high is applied to the
digital input buffer, U9.
Four of the circuits on page two of the
schematic, which include Q2, Q9, Q19
and Q21, are auxiliary I/O connections
wired for future use. They are wired
similar to the remote digital inputs but
include a FET, Q5, Q12, Q20 and Q22,
for digital output operations. To operate
these signals as inputs, the associated
output FET must be turned off. The
FETs are controlled by U10 and U12,
analog input multiplexer ICs.
4.1.2.3 Schematic Sheet 3
U13, U14, U15, U16, U17 and U18 are 3
state non-inverting transceiver ICs that
provide 2 way asynchronous
communication between data busses.
The ICs are used as input buffers to
allow the microcontroller to monitor
various digital input values. The digital
inputs to the ICs utilize a 10 kO pull-up
resistor. The buffer IC, U18, used for
data transfer to the display is wired for
read and write control.
RB1 is the connector to a Rabbit
Semiconductor RCM4300. This Ethernet
enabled controller polls the U1
microcontroller on the same serial lines
as a remote computer. The controller
only gets data and sets conditions
through the serial communications port.
Table 4-1: Innovator DIP Switch
Settings for SW2 located on the Exciter
Controller Board (1310089) in the Power
Supply/Controller Assembly
Switch
Position Function
SW2-1
0 = No Modulator in a translator
configured transmitter
1 = Modulator present in a translator
configured transmitter
SW2-2
0 = Normal
1 = Aural Upconverter not to be
installed
SW2-3
0 = Normal
1 = IP Processor not to be installed
SW2-4
0 = Normal
1 = Modulator not to be installed
SW2-5
0 = Normal
1 = Visual Upconverter not to be
installed
SW2-6 Reserved
SW2-7 Reserved
SW2-8 Reserved
NOTE: These switch positions are
factory set and should not be changed.
4.1.2.4 Schematic Sheet 4
U19 and U20 are digitally controlled
analog switches that provide samples
back to the microprocessor. Each
analog input is expected to be between
0 and 5 VDC. If a signal exceeds 5.1
VDC, a 5.1 Volt Zener diode clamps the
signals voltage, to prevent damage to
the IC. Most signals are calibrated at
their source, however two dual serial
potentiometer ICs are used to calibrate
four signals, System Average Power,
System Aural Power, System Reflected
Power and the Spare AIN 1. For these
four circuits, the input value is divided in
half before it is applied to an op-amp.
The serial potentiometer is used to
adjust the output signal level to between
80 and 120% of the input signal level.
Serial data, serial clock and serial pot
enables are supplied by the
microprocessor to the dual serial
potentiometer ICs. Serial data to the