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5.8 MIX
(Mixer)
BOARD
(X48-1020-10)
(See Figure 24)
Transistor Q2 acts as the first transmitter mixer. It mixes
the transmitter's first IF signal (from the XF board) and the
VFO
output to generate the transmitter's second IF signal
(8 MHz range).
Transistor
Q3
acts as the second
receiver IF mixer.
It
converts the 8 MHz first receiver IF signal to a 3.395 MHz
second receiver
IF signal. The VFO
input is injected into
the
mixer
through
a
3 section
LC
low-pass
filter
to
eliminate harmonics.
The transmit output and receive input circuits include an
electronic
tuner
(VCT) which uses a variable capacitance
diode, D1.
FIGURE
24.
MIX Board
Q4 and Q5 monitor the ALC voltage for the ALC meter
reading. Q6 and Q7 are a detector circuit to detect RF AGC
voltage. Q8 and QQ are a lamp indicator circuit to control
the switch lamps for the external VFO switching.
Y
> ican
F
'OR
no +o
LAMP
Ri2 47K
2 2 S
41t—
25 O01(M)
VFO ——<VFO-INPUT
CN
ia
VR (vcT BIAS! VFO
SW)
Qi,2,3 :3SK35(GR)
Q4 — :2SKI9(GR)
Qs
:2SA495(Y)
in ourpur
age
Qe = :2sas62(Y)
Qs
:28C374(BL)
yy. Vv
Di
:isiess
D23,4:1N6O
Dse sisisss
——- NB33. 3!
ALC Meter
RF-AGC
MIX Unit (X 48-1020-10)
=
FIGURE 25.
MIX Schematic
28
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