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signal that differs in frequency from the signal
frequency.
A mixer is required to obtain a new
intermediate
frequency by combining the signal
frequency
with
that
of
the
local
oscillator
through heterodyne or mixing action,
When the incoming radio signal and the oscillator
signal
are
combined,
the output of the mixer
contains
many
frequencies.
The
output of the
mixer
is
fed
directly
to a highly
selective
amplifier,
called
an intermediate frequency or
IF
amplifier.
This
IF amplifier
accepts
only
one
frequency,
amplifies
it, and
rejects
all
other
frequencies,
From
the IF amplifier the
signal is fed to the audio detector.
From
the audio detector the audio signal is fed
to an audio amplifier which amplifies the signal
so
it can drive headphones
or a loudspeaker,
The
loudspeaker
converts
the electrical
audio
signal
into
sound
waves
that
can
be
heard,
CIRCUIT
DESCRIPTION
RECEIVING
ANTENNA
FREQUENCY
CONVERSION
LOCAL
OSCILLATOR
SELECTION
Assuming the BAND switch to be setfor Band A,
the signal from the antenna is applied through the
BAND
switch, coil L4, again through the BAND
switch,
and
is then coupled across
capacitor
C11 and resistor R1 to the grid oftube V1. Tube
Vi
is
a
combination
oscillator
and
mixer.
IF
AMPLIFICATION
station
frequency,
The
difference
frequency
of 455 ke is calied the intermediate frequency or
IF signal.
The signal from the plate of tube V1 is applied
through the first IF transformer, IF-1, to the grid
of tube V2, IF-1 selects only the 455ke IF signal
and tube V2 amplifies this signal, Tube V2 also
acts as a Beat Frequency
Oscillator
(BFO) to
provide an audible signal for Carrier Wave (CW)
or Single Side
Band
(SSB) reception. From the
plate of tube V2 the signal is applied through
IF-2, which further improves the selectivity of
the receiver, to tube V3.
Tube V3 is a combination detector, audio ampli-
fier and Automatic
Noise
Limiter (ANL)..This
tube detects the audio signal from the IF signal
and amplifies this audio signal. The amount of
SPEAKER
,
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