Icom IC-211 Instruction Manual page 39

8. POWER CIRCUIT
The power circuit of the PLL consists of IC6, 1С7 and ІС8. IC6is a5V voltage regulator
and supplies 1С1, IC2 and IC3, and the display and logic circuits of the driver unit.
IC7 ва DC-DC converter for —9V, and supplies to the AGC circuit of the main unit.
012 is the switch of ІС7, and turns it OFF when the main power switch is turned OFF.
IC8 is an 8.2V voltage regulator and supplies other circuits in the PLL unit, and also
the VCO unit through Q1, a ripple filter.
УСО UNIT
The VCO (Voltage-Controlled Oscillator) is a series-tuned Colpitts circuit, using Q1, and
oscillates in the 133MHz range. The oscillation frequency is controlled by a DC voltage which
is supplied from the loop filter Q7 in the PLL unit to varactor diode D1 inserted in series
with the oscillation coil.
The oscillator output is taken from the source of Q1, and passed through buffer amplifier
Q2 to become the local oscillator signals for the transmitter and receiver. A part of these
signals is supplied to the PLL unit to get a DC voltage to control frequency of the VCO.
DRIVER UNIT
1. FREQUENCY DISPLAY.
IC12 ~ 1C18 are the 7 segment LED indicators for the frequency display. 1C15 ~ IC18
are driven by IC1 — 1С4. The input for the drivers is taken from the BCD output of
IC1, AO ~ D3 in the PLL. 1С14 is driven by ІС5 and IC6. The inputs of A4 and B4
from the PLL unit are decoded by IC5 and IC6 to indicate the MHz digit.
1C12 and 1C13 indicate the 100MHz and 10MHz digits, and display "1" and "4" in any
case.
1MHz DIGIT DISPLAY
SCHEMATIC DIAGRAM
5V
ІС14 СОММОМ АМОРЕ f
dp g |
с а b d e f 9 =
The segments "др" and "с"
of the 1MHz digit are turned
ON in any case.