1)
PLL
LOCAL
OSCILLATOR
F L, the frequency
of
the VCO,
is
controlled by
the
PLL
synthesizer system
as
follows. The
output
frequency
of
the VCO
(I
C5)
is
appl ied
to
one
of
the inputs
of
the In-loop
Mixer
FET4 and mixed
with
the off-set frequency wh ich
is
generated by
the Off-set Oscillator
TR34
or
TR38
and
multi-
plied by three by
Tripier
TR40.
The resultant difference frequencies
are
produced
at the
output
of
F ET 4
as
follows:
F 1
Output
frequency
of
F ET 4
Fo
Off-set frequency, approximately, 11.2858
MHz on AM or USB mode and 11.2842
MHz on
LSB
mode.
3 x
Fo:
33.8575 MHz on AM or
USB
mode.
33.8525 MHz on
LSB
mode.
F 1 falls
into
the
range
of
910kHz
to
1350 kHz in
increments
of
10 kHz.
F
1
is
applied
to
the Programmable Frequency
Divider in the
PLL
Ie,
IC7, after being amplified
by
TR30
and
TR31,
and
then
is
divided by the
programmed-divide-ratio, N, by the Programmable
Divider.
The
resultant frequency
is
applied
to
the
Phase
Detector in IC7
and
is
compared (phase-detected)
with
the reference frequency
of
10 kHz applied
to
another
input
of
the
Phase
Detector.
The
Phase
Detector generates the
control
voltages
for
VCO
to
minimize the difference between F 1
divided
by
N and the reference frequency.
Thus, under locked
condition
of
the loop, the local
frequency
FL
is
locked stable and
is
calculated
by
the
following
formula:
FL
= N x 10 kHz + 3 x
Fo
2)
CHANNEL
SELECTION PROGRAM
The divide ratio, N,
of
the Programmable Frequen-
cy Divider
is
determined by supplied voltages
to
the program
input
terminals, Pin No. 13 through
Pin No. 22
of
the I
C7.
The program
input
voltages
for
Pin No. 19, No. 22
and
No. 23
are
fixed
to
"Iow
level",
and
the
voltages
for
Pin No. 13 through No. 18, No. 20
and No.
21
are
supplied
from
the channel selector
switch S408.
The
function
of
the program
input
terminals
is
as
follows:
Pin No. : 13
14
15
16 17
18
19
20
21
22
Function
:
1A
1B
1C
10
2A
2B 2C
20
3A
3B
Significant 1
2
4
8 10 20
40
80
100200
number
*
Program
Input
"h
igh
level" 19
and
20
are
Kept
"Iow"
(off).
The divide ratio N
of
the Programmable divider
is
provided by the
sum
of
the significant numbers
which
are
effective by supplying
"high
level"
input. For example, when the channel switch
is
set
to
Channel
No.1,
the
input
of
1 A,
2A
and 2D
is
in
"high
level"
and
the others
are
in
"Iow
level".
Therefore, the divide ratio N
is
determined
as
follows:
N
= 1 + 10 +
80
=
91
In the
same
manner, the divide ratio N
for
Channel
No. 1 through No.
40
is
determined
as
shown in
Frequency Chart.
3)
TRANSMITTING
FREQUENCY
CALCULA-
TION
For
an
example, when the
unit
is
operated on
Channel 19, the transmitting frequency
is
calculat-
ed
as
shown in the
following
table
for
each
mode.
AM
mode
LSB mode
USB mode
N
113 113
113
3 x
Fo
(MHz)
33.8575
33.8525
33.8575
N x
10
kHz
(MHz)
1.13
1.13
1.13
FL (MHz)
34.9875
34.9825 34.9875
FIF
(MHz)
7.8025
7.7975
7.8025-
F
t
(MHz)
27.185
27.185
27.185
-
11
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