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The CPU is indirectly linked via the A16 CPU Inter
-
face PCB to the A3 Reference Loop PCB, the A4
Coarse Loop PCB, the A5 Fine Loop PCB, and the
A6 Pulse Generator PCB. The A16 PCB contains cir
-
cuitry to perform parallel-to-serial and serial-to-
parallel data conversion. It also contains circuitry
for many of the rear panel signals, a 13-bit resolu
-
tion DVM, and decoder circuitry for the front panel
rotary data knob optical encoder.
Front Panel This circuit subsystem consists of the the A1 Front
Panel PCB, the A2 Front Panel Control PCB, and
the Liquid Crystal Display (LCD). This subsystem
interfaces the front panel LCD, LEDs, and keys to
the CPU via the dedicated data and address bus.
The front panel rotary data knob is indirectly linked
to the CPU via the A16 CPU Interface PCB.
The A1 Front Panel PCB contains the keyboard ma-
trix of conductive rubber switches. The A2 Front
Panel Control PCB has circuitry to control the LCD
dot-matrix display, turn the front panel LEDs on
and off, and convert keyboard switch matrix signals
to parallel keycode. It also contains the standby/op-
erate line switch logic circuit and the optical encoder
for the rotary data knob.
Frequency
Synthesis
The frequency synthesis subsystem consists of the
A3 Reference Loop PCB, the A4 Coarse Loop PCB,
the A5 Fine Loop PCB, the A7 YIG Loop PCB, and
the A11 FM PCB. It provides the reference frequen
-
cies and phase lock circuits for precise control of the
YIG-tuned oscillator frequencies, as follows:
The A3 Reference Loop PCB supplies the sta
-
ble 10 MHz and 500 MHz reference frequency
signals for the rest of the frequency synthesis
system.
The A4 Coarse Loop PCB generates coarse
tuning frequencies of 219.5 to 245 MHz for use
by the YIG Loop.
The A5 Fine Loop PCB provides fine tuning
frequencies of 21.5 to 40 MHz for use by the
YIG Loop.
The A7 YIG Loop PCB performs phase detec
-
tion of the YIG-tuned oscillator’s output fre
-
quency and provides a YIG loop error voltage
to the A11 FM PCB.
The A11 FM PCB processes the YIG loop error
voltage, producing a correction signal that is
2-4 682XXB/683XXB MM
FUNCTIONAL 682XXB/683XXB
DESCRIPTION MAJOR SUBSYSTEMS