Icom IC-R7O Maintenance Manual page 25

4. Band signals
Note that the band signals relative to each frequency are as follows.
Frequency Band signal
(MHz) (4 bit)
0 ~ 1.999
2.0 ~ 3.999
4.0 ~ 7.999
8.0 ~ 10.999
11.0 ~ 14.999
15.0 ~ 21.999
22.0 ~ 29.999
5. Band-pass filter and VCO switching signal
Band-pass filter switching signals corresponding to display output signals of the CPU are output from
Cy ~ C3 terminals. IC15 is the decoder for these 4-bit signals. These signals are multiplexed into signals,
0 ~ 9, and output to the RF unit and PLL unit through buffers, IC20 and 1IC21, for use as band-pass filter
switching and VCO switching signals.
The band-pass filter switching signal for each frequency is as follows:
Frequency Signal (4-bit)
(MHz)
ie) 3
BPF vco
0 ~ 1.599
1.6 ~ 1.999
2.0 ~ 2.999
3.0 ~ 4.999
5.0 ~ 7.999
8.0 ~ 10.999
11.0 ~ 14.999
15.0 ~ 21.999
22.0 ~ 27.999
28.0 ~ 29.999
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6. Mode signal circuit
Mode signals are output from the CPU's E port, and are latched at 1C16 by the load signals from the Io
terminal. 1C18 is the decoder for this operation, where the signal is decoded into each mode signal and
output through buffers IC5 and IC21. Note that, because there is no program in the CPU, FM mode
signals are produced by IC19, Q9, Q10, etc.
The mode signals also produce segment signals a ~ d to extinguish those segments unnecessary for
display of the mode by the display unit.
The mode signals relative to each mode are as shown below.
Mode signal
Mode (4-bit)
AM (FM)
CW-N
LSB
USB
CW
RTTY