V,R PC
EOARD
aÁ-5t57
IC FC EOARD
AÁ-5r56
TOUC|I
SW|ÍCH
PC BOARo ÁA-5r58
Fig.6 Block Dias.am
t:
L
t--
3) Acrual
Operation
Fig. 5 is a cÍcuit diagram of the high
fr€qu€ncy
amplifier stase only
of a circuit which is actually
used. Condenser
Cl and varactor diode Dl in
the diagram are equivalent to the variable
con,
denser of
an
ordinary
FM fÍont end. As can be
understood
from Fig. 3, Dl varies the capacitance
in a 4 to 16 PF ranSe
by means oí inverse bias
voltage.
This capacitance and condenser
Cl
combined caFcitance forÍns the Íesonance
circuit
with coil LA. Consequently, it is satisfactory
if
at
low.esonance
íÍ€quency, the voltage
supplied
to the varactoÍ diode d€clines,
and at hid re-
sonanc€ frequency, the voltage
supplied to th€
varactor
diod€ increas€s.
This
voltage
variation
method with variabl€ resistor, êtc.,
op€rates
in
the
sam€ way as a regulaÍ variable
cordenser.
FiE.7
This
method uses a local
oscillator circuit
and
frequency mixer
circuit, and
bias voltage is
applied
to the varactor diode
for starioo
selection and is
called a
varactor
tuneÍ. Pleas€ r€fer
to the scheÍ,a-
tic diagran
foi
actuai
circuit drawing.
II
V
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