Heathkit GR-54 User Manual

Page 58
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SUppréesses unwanted aqjacent sign is and ma
the Receiver more selective,
es
The signal from the crystal filter is fed to the
control grid of the first IF amplifier tube V3,
The amplified signal from V3 is coupled through
capacitor C31 to the control grid of the second
IF amplifier tube, V4,
From the plate of tube V4 the IF signal is coupled
through
capacitor
C39
to
the
detector,
Crystal diodes CR&3 and CR4 detect the audio
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modulation from the IF signal,
AVC AND ANL CIRCUITS
With the AVC {automatic volume control) switch
turned on, some of the signal from the plate of
tube V4 is rectified by crystal diodes CRi and
CR2, This DC voltage, which increases or de-
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the control grid of tubes V1, V3, and V4, This
AVC voltage controls the amount of amplification
of these tubes, providing a more constant signal
level at the speaker,
With the ANL (automatic noise limiter) switch
turned on, diodes CR5 and CR6 are connected
into the circuit, These diodes, which limit the
peaks of the AF signal, clip off the noise pulses
such as static and ignition noise, that are often
present on the signai,
The signal from the plate of second IF ampli-
fier tube V4 is coupled through capacitor C47
grid of product getector tube V5B
the
a USB signal, the Mode switch i
no:
Ss
osition, This turns on produc
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stage V5B and BFO (beat frequency oscillator)
stage V5A. The BFO is tuned by coil L18 to the
carrier frequency necessary for proper SSB
(single sideband) or CW detection, For an LSB
signal the Mode switch is placed in the LSB
position, The BFO is then tuned to a lower
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frequency by capacitors C46 and C49
Product detertor fue V5B mixes the single
sideband or CW
The audio signal from the AM detector or
product detector is coupled through resistor
R53 and capacitor C51 to the control grid of
first audio amplifier tube V6A. V6A ampli-
fies the signal and then couples it through
capacitor C52 io the control grid of audio
output tube V6B, The signal is amplified by tube
V6B and then eounled throuch audic output
waves Sn Od oe ee od
transformer T2 to the speaker or headphones,
Capacitor C56 provides high frequency feedback
for distortion cancellation, and stability.
POWER SUPPLY
The power supply is a full-wave rectifier, con-
csictinge of dindseac«c CR? and CRA and nower
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transformer T3, The DC voltage is filtered by
resistors R49, R50, R51, and R52 and capac-
itors C57, C58, C59, C60, and C61,

Heathkit GR-54 Specifications

General

Brand	Heathkit
Model	GR-54
Category	Receiver
Language	English