Icom IC-701 - Page 33

goes LOW and Pin 1 goes HIGH. When the band is 1.8MHz,
Pin 13 of 1C11 is HIGH and Pin 11 is connected with Pin 1
of 1C10, so it is HIGH.
As Pin 12 is connected to the front of the inverter of the
oscillator circuits, the three input gates of IC11 are all
HIGH in the next half cycle, and the output from Pin 10
goes LOW. 1C13’s output HIGH level pulse is fed to IC1 in
the PLL as K8, therefore the 100KHz digit is set at 8.
When the band is 3.5MHz, it is input to K1 and K4 through
the same process and the 100KHz digit is set to 5. As the
100KHz digit begins with O in upper bands from 7MHz,
this operation is not necessary. When the band is 7MHz or
ACC
FCL Ks Ka Ko K2 Kj
e C) e O) OO @
1.8MHz 3.5MHz
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LOW EDGE PRESET CIRCUIT
TIMING CHART
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above, the band data of 1.8MHz and 3.5MHz are LOW, so
pin 6 and Pin 10 of IC11 are always HIGH and this circuit
does not work.
After the third pulse from IC8, it is used together with the
low edge of the band and fed to IC1 in the PLL as the KO
input.
6-4-5 MATRIX CIRCUIT
The output AO0-A4 of the LSI and the signal of each band
make up the matrix circuit and this decides the edges of
each band.
The band edges are as follows:
21 MHz | 21.000.0 21.499.9 21.490.0
* In the 28MHz band the tuning does not stop when the
band edge is reached. It automatically reverts to the
other band edge and continues tuning either up or down.
1021, 1C20, and IC18 of the driver unit detect the 0 in the
10KHz, 1KHz, and 100Hz digits. Since they are AND gate
circuits, they detect when all three figures are 0, and are
used to control the low edge. !C19 detects O of the
100KHz level, but it is necessary to distinguish the 1.8MHz
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