Specifications

R.5.3 Transmitter Control/Fault Logic PAL
The function of this PAL is to control the transmitter mode
depending on the frequency control mode. The transmitter
should be shut OFF when the frequency is changed and major
component values are switched. The transmitter must be oper-
ated at LOW and HIGH power during the initial tune up stage in
changing frequency. The fault logic section also determines what
action to take when a fault occurs in the frequency change
circuitry.
Refer to Figure R-1, TX CTRL/FLT PAL, for the following
discussion.
R.5.3.1 Control Inputs
The inputs to the PAL are the active high Tune Mode Data from
the Frequency Control board at J19, the internal 12.5Hz Control
Clock, and the logic high Auto Tx Power Control input from JP4.
Note that the Normal Mode input does not connect to the PAL.
R.5.3.2 Control Outputs
All control outputs of the PAL are active high, and inverters
present open collector active low signals to the Transmitter
Interface board at J18.
R.5.3.2.1 Frequency Change Mode
When the Frequency Change input goes logic high, simultane-
ously the RF MUTE and TX OFF outputs of the PAL also go
logic high and the transmitter is shut OFF. The 12.5 kHz Clock
is connected to the Band Latch Pulse Generator, which will
generate a 100mS Band Latch Pulse output (after a delay) at TP2
when both entering or exiting the Frequency Change mode. This
pulse will allow new Frequency Band Data to be latched by U6.
This Band Latch output is also used by the Frequency Synthe-
sizer Interface at J17 and the Frequency Control board at J19.
R.5.3.3 Fault Inputs
Internal fault inputs to the PAL are Bandswitch, Power Supply,
Efficiency Coil, Tune, and Load. External fault input are Synthe-
sizer at J17 and Frequency Control Power Supply at J20. All fault
inputs are active low, except for Bandswitch and Efficiency Coil
faults which are active high.
R.5.3.4 Fault Outputs
When any fault input goes active low, the PAL will produce an
RF MUTE and the power output will drop to 0kW to protect the
transmitter.
The 5 active low fault outputs are connected to the Frequency
Control board at J20 for illuminating the corresponding fre-
quency control front panel LED indicator RED. Note that a
Bandswitch Fault could either be a Bandswitch or Efficiency
Coil Fault and a Power Supply Fault could be for either the
Frequency Control board or the Frequency Control Interface
board.
R.5.4
Band Switch Encoding
To optimize the frequency tuning process, the bandswitching is
done in binary fashion. This will produce a fairly flat response
with frequency.
To allow the 6 Bit input Band Select Data to switch the resultant
circuit at the proper point, a Band Encoder is used to encode the
6 bit input band into the desired output band whether it is a 1 to
6 bit output.
Figure R-1. TX CTRL/FLT PAL
888-2339-002 R-3
WARNING: Disconnect primary power prior to servicing.