Each
1st LO
signal
(69.1115-99.0015
MHz)
enters the
RF unit
from the
PLL
unit
via PI or P2. The
LO
signals are
amplified at
Q1 or
Q8,
filtered by a
low-
pass
filter,
and then,
applied to
each 1 st
mixer.
1st
IF frequency
Mode Frequency
SSB 69.0115
MHz
CW, RTTY 69.0106 MHz
AM, FM 69.0100
MHz
The detected voltage is
also applied
to
the noise blanker
AGO circuit
(Q52)
and
is
then fed back to the noise ampli-
fiers
(Q47-Q49)
as a bias
voltage.
The
noise AGO circuit
prevents closure of the noise
blanker
gate
for long periods
by non-pulse-type
noise. The time constant of the noise
blanker AGO circuit is
determined
by R55
and
C41
.
Q54-
Q56
expand the
blank width when [NB WIDE] is turned ON.
The [BLK-WIDTH] control
adjusts the blank width.
4-1-5
1st IF CIRCUIT
(RF UNIT)
The signals from the noise blanker gate
are then applied to
the 2nd
IF circuit.
The
1st IF
circuit filters and amplifies the 1st IF
signals. The
1st IF
signals
combined at L34
are applied to an MCF
(Monolithic
Crystal Filter; FI1)
to suppress out-of-band
signals.
The
levels of
the
converted
1st
IF signals are adjusted at
PIN
attenuators (D1, D3, D4
and
D5,
D7, D8)
controlled
by
the
[BALANCE]
control. The
signals are applied to a 1st IF
amplifier
(04
or 01
1)
and then
combined
at
L34.
The
combined
signals pass through the pair of
MCF’s (FI1)
and
are
amplified at 015. The signals
are applied to the
2nd
mixer (IC34)
in the IF unit via P3 (IF unit J8).
The AGC
voltage is
supplied to the 2nd
gate of Q15.
4-1-6
2nd
MIXER CIRCUIT
(IF
UNIT)
The 2nd
mixer circuit mixes the
amplified 1st IF
signals
and
2nd LO
signal
(60.00
MHz) to
convert
the 1st
IF to a 2nd IF.
The 1st IF
signals from
the RF unit are converted to 9
MHz
2nd IF
signals at the 2nd
mixer
(IC34).
The 2nd
IF
signals are 2nd IF frequency
applied to FI1 to
suppress
undesired
signals such as
the 2nd LO
signal, and are
then
applied to
the noise
blanker gate
(D68-D71).
Mode
Frequency
SSB 9.0115
MHz
CW, RTTY
9.0106 MHz
AM, FM 9.0100 MHz
4-1-7
NOISE BLANKER
CIRCUIT (IF UNIT)
The
noise
blanker circuit detects
pulse
type noise,
and turns
OFF the
signal line when
noise appears.
The
2nd IF signals
from FI1 are applied to the noise
blanker
gate (D68-D71).
A
portion of the signals from FI1 are
amplified at
the noise amplifiers
(Q47-Q49),
then
detected
at the noise
detector (D75) to
convert
the noise
components
to DC
voltages.
The
signals are
then applied to the noise
blanker switch
(Q57-Q59).
At the moment the
detected voltage exceeds
the
Q59’s or Q58’s
threshold
level,
Q57 outputs a
blanking
signal to close
the noise blanker gate (D68-D71) by
apply-
ing
reverse-biased
voltage.
Q58
and
Q59
are activated by
narrow-width pulses and
high level pulses, respectively. The
[NB
LEVEL]
control adjusts the threshold
level
of Q58
and
Q59.
4-1-8
2nd IF CIRCUIT
(IF
UNIT)
The 2nd IF circuit amplifies
and filters the 2nd IF signals.
The
signals passed through the
noise blanker gate
(D68-D71)
are amplified at Q46
and applied to a 2nd IF
filter as
shown in the following table.
2nd IF filters
Mode
Used filter Control signal
CW/RTTY wide,
SSB med., AM nar.
FL-80
(FI2) 2N24
CW/RTTY med.
FL-32A (FI3) 2N05
CW/RTTY
nar. Optional
FL-1
01 2NCO
SSB wide,
AM med.,
FM nar.
Optional
FL-1 02
2NAO
SSB nar.
Optional FL-223 2NSO
AM wide, FM med.
Bypassed 2NTH
The
filtered or bypassed
signals
are then
applied to the 3rd
mixer
circuit through a buffer amplifier
(Q38).
4-1-9
3rd MIXER
AND 3rd IF CIRCUITS
(IF UNIT)
The 3rd mixer
circuit mixes the 2nd IF signals and the 3rd
LO
signal to obtain the 3rd
IF
(455
kHz)
signals.
The 2nd IF signals from Q38
are applied to the 3rd mixer
(IC18 pin
6).
The 3rd LO
signal
from
the PLL unit is applied
to the 3rd
mixer
(IC18
pin
8).
The 2nd IF signals are
converted to 3rd IF signals. The 3rd IF
signals are
ampli-
fied at
Q39,
and then applied to one of the 3rd IF filters.
3rd IF filters
Mode
Used filter Control signal
CW/RTTY wide,
SSB med.,
AM nar.
FL-96
(FI4) 3R26
CW/RTTY med. FL-52A (FI5) 3R05
SSB
wide, AM med.,
FM nar.
CFW455HT (FI6)
3R60
AM wide, FM med. CFW455E (FI7)
3RFM
CW/RTTY nar.
Optional FL-53A 3RCO
SSB
nar. Optional FL-222 3RSO
4-2
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