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filtered before amplification by Q2019
main loop Q2012 (uPC1037H) as a sub-loop
Although the reference frequency of the
main loop is 81.92 kHz, a 10 Hz receiving
frequency step is obtained by mixing a sub-
loop Signal with the main loop. The VCO is
thus Phase-locked to the reference Signal.
Miscellaneous Con trol Logic
Band selection for the PLL Loop 1 Local
Q2005 (M14558CP) and switch driver 42040
Circuit Description
of Q2030) controlled by Q2027 (BAlA4P) sig-
nals the CPU, which then mutes receiver
audio and blinks the display until the PLLs
resume leck.
The MPU provides band (BPF) selection on
the Main Unit via latch Q1032(SN74LS145N),
and mode/filter selection using switching
gates Q1023-2-Q1023-4 and Q1054.
Rotary encoded tuning data from the main
dial is processes by dial counter Q2044
S-bit data bus. Q2041 contains a real-time
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