Voltage-Controlled Oscillator (U5)
The VCO uses a low-noise, high-gain transistor as the
basic oscillator. The resonant circuit, which determines the
frequency of oscillation, is formed by a high-Q SAW which
is used to set the center frequency at the factory. The output
of the VCO is coupled into a cascade amplifier which pro-
duces 0 dBm. The output of the RX-VCO amplifier is cou-
pled into the receive first double-balanced mixer circuit Z2
through amplifier Q103. The VCO amplifier output is also
connected to the input of TX-amplifier transistor Q104.
VCTCXO Reference Oscillator (Z1)
The Z1 oscillator module is self contained, fully tempera-
ture compensated and operates at a frequency of 13.2 MHz.
The oscillator also has modulation capability. Frequency is
adjusted by a trimmer while monitoring the transmit circuit
output at the antenna jack.
LOGIC CIRCUIT
The logic circuit consists of control circuits and audio
circuits (Figures 4 and 5). Physically, this circuit consists of
two circuit board as follows:
•
Control Board Assy.
•
LED Flex Assy. (M-RK I)
•
LCD/KB flex Assy. (M-RK II & Scan)
Control Board Assy.
The Control board consists of the following circuits (re-
fer to Figures 4 and 5):
•
CMOS Microprocessor (U1, U2)
•
E
2
PROM (U6)
•
Flash E
2
PROM (U4)
•
Custom CMOS DSP Chip (U3)
•
Custom CMOS ASP Chip (U7)
•
CMOS Inverters (U12)
•
CMOS OR gates (U15)
•
CMOS SRAM (U5)
•
Audio Amplifier (U11)
•
5 volt Regulator (U9,10)
Microcomputer
The main microcomputer circuit in this radio consists of
microprocessor, HD6475328FI1O (U2), 2 Kx8E
2
PROM
(U6), 128 K x 8 flash EPROM (U4), 8 K x 8 RAM (U5), and
custom DSP (U3). This circuitry runs at a 9.8304 MHz rate
determined by crystal Y1 and controls the radio through a
second microprocessor HD6473308FI6 (U1). This micro-
processor (U1) runs at an 4.9152 MHz rate. The 4.9152 MHz
rate is determined by DSP (U3).
•
Controlling the DSP, flash E
2
PROM and RAM
•
Loading data to the frequency synthesizer
•
Fetching and processing the PTT, monitor, channel
selection, and volume control
•
Controlling the LED display (M-RK I)
•
Loading data to the LCD display processor (M-RK II
& Scan)
•
Controlling the audio circuit (processor)
•
Decoding the squelch
•
Encoding/Decoding the Channel Guard and Digital
Channel Guard
•
Controlling the loading interface for the radio data
(channel number and signaling)
Flash E
2
PROM (U4)
IC U4 contains the software to control the microproces-
sor.
RAM (U5)
This RAM has a storage capacity of 64 Kbits up to 256
Kbits depending on software version.
E
2
PROM (U6)
This E
2
PROM has a storage capacity of 2 Kbit x 8. This
personality controls various functions of the radio. The per-
sonality data is entered from outside the radio through the
UDC connector to the microprocessor and then to the
E
2
PROM. The data mainly consists of the following:
•
Channel frequency Data
•
CG/DCG data
•
TX Power, TX Modulation Data
•
Squelch Data
•
Display Data, etc.
LBI-38735
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