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The
amplified
signal
is
fed
through
a
double-tuned
filter
composed
of
L32,
C77
and
L33
to eliminate spurious
components, and
then
fed to the
Q12
and
Q13
transmit mixer.
The
frequency
of the
local
oscillator
ranges
from 70.5515
~
100.4515MHz
which
converts the
IF
signal
to the desired
frequency
of
0.1
~
30MHz.
In
the transmit
mode,
D45
is
turned
ON
and
the
signal
is
amplified
about
20dB
by
the
Q14
wideband
amplifier
and
is
output
to the
PA
unit
through
J8.
Cl
71
and
R86
are
provided
to taylor
the
fre-
quency
characteristics.
(2)
PA CIRCUITS
The
RF
signal
input
from
the
RF
unit
through
PI
is
amplified
by
the
Q1
class
A
amplifier.
The
output from
Q1
is
converted
to
a
balanced
output by
LI
and
is
amplified
by
the
Q2
and
Q3
class
AB
push-pull amplifier.
The
negative
feedback
circuits
inserted
between
the
collector
and
the base of
Q2
and
Q3
provide
wide frequency
characteristics.
The
idling
current of
Q2
and
Q3
is
controlled
by
the
junction voltage of
D1.
The
current
is
set at
about
100mA
by R27,
R30
prevents the
set
value
from
deviating
due
to variations of
D1
characteristics.
The
output
of
Q2
and
Q3
is
fed to
the
L4 impedance
matching
section
and
is
amplified
by
the
Q4
and
Q5
class
AB
push-pull
am-
plifier
to provide
100
watts
output power.
11-3 PLL CIRCUITS
The
PLL
unit
outputs
two
oscillator signals
for
the
RF
unit,
i.e.,
the
variable
first
local oscillator
output
(1st
LO)
of
70.55
~
100.45MHz
necessary for
the.
first
mixer,
and
the fixed
local oscillator
output
(2nd
LO)
of
61.44MHz
necessary for the
second
mixer.
In
addition,
the
marker
signal
is
also
generated
in
this
unit
and
is
sent to the
RF
unit.
•
PLL
1C
CHIP
IC1
(M54929P)
is
a
multi-function 1C containing
a
phase comparator,
a
programmable
divider,
a
reference
frequency
oscillator
circuit, a
divider
and
a
swallow counter
controller.
By
using
this
1C with
IC2
(M54466L,
a
swallow
counter),
it
can perform
pulse
swallow
dividing.
[MAIN LOOP]
Reference
Frequency
(10kHz)
(3960
~
6950)
1st
LO
[MARKER GENERATOR]
MARKER
MARKER
OUTPUT
10kHz
X
n
-51 -
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