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13
When the local oscillator frequency is varied and ''fr'' and
"€L'"' are equal, the phase sync loop is locked.
fL'
fL
fL/20N
= fr
20Nfr
By changing the value of N (an integer) fed from the micro-
computer
to the
1/N
programmable
counter,
the
local
oscillator
frequency
can
be varied
in 20fr steps. When
tuning
FM in 200 kHz steps, the value of N = 2N' (N':
integer)
is fed from
the microcomputer.
Proper tracking
adjustment
between
the tuning
circuit
for the antenna
and
RF amplifier and
the local oscillator tuning circuit
enables reception of the desired station.
The microcomputer programs the relationship between the
receiving
mode,
intermediate
frequency
and
the
value
of N and feeds the data of the receiving frequency via the
driver to indicate the tuned frequency on the fluorescent
tube indicator.
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