Specifications

Todo this a programmable devicePAL is used for flexibility. This
programmable device can therefore be changed easily without
circuit board changes.
R.5.5
Relay Encoding Example
NOTE
Refer to the Transmitter Band Chart, for the following examples.
Refer to Figure R-1 PAL Encoder for the following example.
For example, if the Frequency Band is 36 (1000 kHz transmitter
frequency) and the Encoder is for the Driver Relay Drive, the
Driver Band is 17. The output of the Encoder will be as follows:
OUTPUT ENC OUT DEC EQUIV PAL OUTPUT
Bit 5 0 32 1
Bit 4 1 16 16 0
Bit 3 0 8 1
Bit 2 0 4 1
Bit 1 0 2 1
Bit 0 1 1
10
BAND = 17
Since this Encoder is for Relay Drivers, all 6 outputs from the
Encoder are connected to the PAL output via inverters.
R.5.5.1 Relay Drivers
When the PALoutput is logic high, the open collectorrelay driver
output at J21 will be +24VDC. The relay connected to the output
will be de-energized.
When the PAL output is logic low, the open collector relay driver
output will be connected to ground. The relay connected to the
output will be energized.
R.5.6
Active High Output Encoding Example
For example, if the Frequency Band is 36 (1000 kHz transmitter
frequency) and the Encoder is for the Synthesizer Sync, the Band
is 50. The output of the Encoder will be as follows:
OUTPUT ENC OUT DEC EQUIV PAL OUTPUT
Bit 5 1 32 32 1
Bit 4 1 16 16 1
Bit 3 0 8 0
Bit 2 0 4 0
Bit 1 1 2 2 1
Bit 0 0 1
0
BAND = 50
Since this Encoder is a Active High Output, the PAL outputs will
be the same as the Encoder Outputs.
R.5.7
Bandswitched Circuits
The following circuits require switching of some type of reac-
tance to track the operating frequency. A description of what is
required to change is included in this section, refer to the Output
Network Schematic 843-5155-553 and the Power Amplifier
Schematic 843-5155-551 for the following discussion.
R.5.8
COMBINER PAL
The COMBINER PAL receives the Band Select Data and en-
codes the outputs for the Efficiency Coil boards, 1C1, 2L1, and
2C5.
R.5.8.1 Efficiency Coil Band Switching
For optimum transmitter efficiency, the efficiency coils must be
switched at various transmitter bands. This 2 bit system basically
switches two relays in binary fashion to achieve the four induc-
tance values. Each relay is a DPDT type and two contacts are
switched at once.
Refer to Sheet 1 of the schematic for the Efficiency Coil board
839-7930-503 for the following discussion.
R.5.8.2 Efficiency Coil Relay Drivers
There are 20 Efficiency Coil boards located in the Left, Center,
and Right Compartments and on the Driver Section. Each Effi-
ciency Coil has 8 relays on the board.
All the odd number relays of the Efficiency Coil boards are
connectedtotheB0MOSFETswitchQ2atJ3throughJ6.All
the even number relays of the Efficiency Coil boards are con-
nected to the B1 MOSFET switch Q2 at J3 through J6.
Figure R-2. PAL Encoder
R-4 888-2339-002
WARNING: Disconnect primary power prior to servicing.