Icom IC-720 Instruction Manual page 25

the rotation of the tuning knob. The input to the CPU is
determined by the selected mode and band. From the CPU
the дата is sent to the I/O for output control, the PLL Unit,
the LED Control IC, and the 1/0 input control.
LOGIC UNIT BROCKDIAGRAM
to
PLL
MODE-FUNCTION
=
"оту
ту и
112) ии пат
"DISPLY DATA
Au
[]
1 Li
IL
U
ONV.
=
T
каде RE
|
TUNE
ӨР, DOWN UP*DOWN СЫ === рия
to
CONT.
to
D
ROTARY RL
ROTARY
RL.
Yn
Sw.
from
|. перат та:
ROTARY RL.
CODE
CONV.
BUFF
to
>> В.Р.Р.
6-9 PLL UNIT
This unit is composed of three Phase-Locked Loops, two
VXOs, and the multiplex circuit. One VXO operates the
multiplex and provides control for the 100Hz and 1KHz
steps of the lowest two digits of the VCO output frequency.
Control for less than 100Hz of the frequency is provided by
the VXO in the PLL Unit. The reference frequency output
of the VXO is determined by a crystal with an output
PLL UNIT BLOCKDIAGRAM
2nd LO
30.72 MHz
10.24Mhz VXO1
Freg.
Tripler
1st LO
39.7315 ~69.8314 MHz
г Crystal
oo
TW osc.
{ РЕ — Buffer
[
Crystal
OSC. Buffer |
= v со - Buffer
== 10.24MHz
LoopC
y =
Interface \
2.91~
12.9 MHz
Loop A
trom % Conv.
1 къ 10Hz Step 23 Divider төн, Ё Р a
|
512M
100Hz Step
Cont.
100КН2 Step
ont.
Ве
6-10 RTTY UNIT
іп transmit this unit provides the Mark frequency and
Space frequency for RTTY. From the Accessory Socket on
the rear panel it provides the source for a demodulator in
During transmit, it controls the oscillator of a
teletyperwrite when it is connected to the Accessory
Socket. The Mark signal is 9.0106MHz and the Space
receive.
signal is 9.01077MHz, both of which are generated by the
RTTY Unit. These signals аге sent directly to the RF Unit's
2nd mixer and
1st mixer then to the Double
Balanced
Modulator where they are modulated by the signals from
the PLL
Unit local oscillator, the frequency obtained is
sent through the Band Pass Filter to the Driver Unit.
203 >