AM RECEIVER BEE jay

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AM RECEIVERBEE jay
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Who was the inventor that put the grid in the
vacuum tube making the first voice and music
amplifier?
3
Who was the inventor that put the grid in the
vacuum tube making the first voice and music
amplifier?
Lee Deforest
4
Who invented the Superheterodyne principle and
later Frequency Modulation?
5
Who invented the Superheterodyne principle and
later Frequency Modulation?
Maj. Edwin Howard Armstrong
6
Name the president of RCA who manufactured the
Superheterodyne receivers.
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Name the president of RCA who manufactured the
Superheterodyne receivers.
David Sarnoff
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Name 4 external factors that affect the reception
of a signal and make the receivers job difficult.
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Name 4 external factors that affect the reception
of a signal and make the receivers job difficult.

• Weak signals
• Adjacent stations
• Noise
• Fading

10
Name the parts of the simplest AM receiver
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Name the parts of the simplest AM receiver
Antenna, ground Tuner Detector Transducer or
earphones
12
Name the circuit used for the tuner.
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Name the circuit used for the tuner.
Variable LC bandpass filter
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A variable capacitor depends on
a. applied voltages being variable b. the plate
separation being adjustable c. pressure on the
dielectric being adjustable d. provisions for
feedback
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A variable capacitor depends on
b. the plate separation being adjustable
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Name the circuit used for the detector and the
material it is made from.
17
Name the circuit used for the detector and the
material it is made from.
Germanium diode
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Why is a germanium diode better than a silicon
diode in an AM Receiver?
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Why is a germanium diode better than a silicon
diode in an AM Receiver?
Germanium diode turns on with a forward bias of
0.3V, silicon turns on at 0.7V.
20
A typical receivable signal level in an AM
receiver may be as low as 10 uV.
True or False?
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A typical receivable signal level in an AM
receiver may be as low as 10 uV.
True
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Name the two receiver designs that followed the
crystal radio.
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Name the two receiver designs that followed the
crystal radio.
TRF and Superheterodyne
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What circuit was added to the crystal radio to
make the TRF Receiver?
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What circuit was added to the crystal radio to
make the TRF Receiver?
Amplifier
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What does the letters TRF stand for?
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What does the letters TRF stand for?
Tuner Radio Frequency Receiver
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The ability of a receiver to choose a desired
signal frequency while rejecting closely adjacent
signal frequencies is known as _______________.
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The ability of a receiver to choose a desired
signal frequency while rejecting closely adjacent
signal frequencies is known as _______________.
selectivity
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Which circuit provides the selectivity in the TRF
receiver?

• IF AMP
• LC Bandpass in tuner
• Detector

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Which circuit provides the selectivity in the TRF
receiver?
B. LC Bandpass in tuner
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What is the alpha designator for the measure of
the sharpness of a filter?
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What is the alpha designator for the measure of
the sharpness of a filter?
Q
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How is the Q of a filter calculated?
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How is the Q of a filter calculated?
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A bandpass filter is resonant at 4MHz and has a 3
dB bandwidth of 100kHz. What is the filters Q?
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A bandpass filter is resonant at 4MHz and has a 3
dB bandwidth of 100kHz. What is the filters Q?
38
A bandpass filter has a Q of 100 and is resonant
at 1MHz. What is the filters bandwidth?
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A bandpass filter has a Q of 100 and is resonant
at 1MHz. What is the filters bandwidth?
40
Name each stage of the TRF Receiver and state
its function. (One per contestant.)
41
Name each stage of the TRF Receiver and state
its function. (One per contestant.)
RF
RF
STAGE
STAGE
RF Stage- filters the desired station and
amplifies weak antenna signal
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Name each stage of the TRF Receiver and state
its function. (One per contestant.)
RF
RF
DETECTOR
STAGE
STAGE
RF Stage- filters the desired station and
amplifies weak antenna signal DETECTOR- removes
information from the carrier
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Name each stage of the TRF Receiver and state
its function. (One per contestant.)
RF
RF
AF
DETECTOR
STAGE
STAGE
AMP
RF Stage- filters the desired station and
amplifies weak antenna signal DETECTOR- removes
information from the carrier AF Amp- power
amplifier to drive the speaker
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Name two disadvantages of the TRF Receiver design.
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Name two disadvantages of the TRF Receiver design.
Bandwidth varied with tuning. LC components
varied with temperature and age.
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Explain the Superheterodyne principle.
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Explain the Superheterodyne principle.
All incoming stations are down converted to a
common IF frequency before demodulation.
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Name each stage of the Superheterodyne Receiver
and state its function. (One per contestant.)
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Name each stage of the Superheterodyne Receiver
and state its function. (One per contestant.)
RF
STAGE
RF Stage- filters the desired station and
amplifies weak antenna signal
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Name each stage of the Superheterodyne Receiver
and state its function. (One per contestant.)
RF
STAGE
LO
Local Oscillator- produces a sinewave 455kHz
above the incoming RF
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Name each stage of the Superheterodyne Receiver
and state its function. (One per contestant.)
RF
MIXER
STAGE
LO
Mixer- combines RF and local oscillator producing
the sum and difference
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Name each stage of the Superheterodyne Receiver
and state its function. (One per contestant.)
RF
IF
MIXER
STAGE
STAGE
LO
IF STAGE- filters off the sum, passes the
difference and amplifies the 455KHz to a level
that turns on the detector.
53
Name each stage of the Superheterodyne Receiver
and state its function. (One per contestant.)
RF
IF
MIXER
DETECTOR
STAGE
STAGE
LO
DETECTOR- removes the information from the
carrier and develops AGC voltage
54
Name each stage of the Superheterodyne Receiver
and state its function. (One per contestant.)
RF
IF
AF
MIXER
DETECTOR
STAGE
STAGE
AMP
LO
AF AMP- power amp to drive the speaker.
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The greater the gain of the receiver, the better
its ___________________.
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The greater the gain of the receiver, the better
its ___________________.
sensitivity
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Most of the gain and selectivity in a superhet is
obtained in the

• RF amplifier
• Mixer
• IF Amplifier
• AF Amplifier

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Most of the gain and selectivity in a superhet is
obtained in the
C. IF Amplifier
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An RF amp has an input signal of 20uV containing
2uV of noise. What is the input signal-to-noise
ratio in dB?
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An RF amp has an input signal of 20uV containing
2uV of noise. What is the input signal-to-noise
ratio in dB?
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The RF amp has gain of 100 and adds 40uV of
noise. What is the output signal-to-noise ratio
in dB?
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The RF amp has gain of 100 and adds 40uV of
noise. What is the output signal-to-noise ratio
in dB?
63
Amplifier gain can be used to improve the
signal-to-noise ratio of a received signal.
True or false?
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Amplifier gain can be used to improve the
signal-to-noise ratio of a received signal.
False. Analog amplification always adds noise.
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What is the name of the transistor in the front
end of the RF Amplifier called?
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What is the name of the transistor in the front
end of the RF Amplifier called?
Preamplifier
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What is the name of the special transistor used
in the front end of a UHF RF Amplifier called?
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What is the name of the special transistor used
in the front end of a UHF RF Amplifier called?
Dual gate MOSFET
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Name two advantages of using a dual gate MOSFET
transistor in the AM receivers front end.
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Name two advantages of using a dual gate MOSFET
transistor in the AM receivers front end.

• Hi input impedance (Z)
• Low noise
• 2nd gate for AGC

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What does the letters AGC stand for?
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What does the letters AGC stand for?
Automatic Gain Control
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What is the purpose of the Automatic Gain Control?
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What is the purpose of the Automatic Gain Control?
Levels out variations in received signal strength
by varying gain.
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In what stage of the Superheterodyne Receiver is
the AGC voltage developed?
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In what stage of the Superheterodyne Receiver is
the AGC voltage developed?
Detector
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What stage or stages of the Superheterodyne
Receiver is the AGC voltage applied to?
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What stage or stages of the Superheterodyne
Receiver is the AGC voltage applied to?
RF and/or IF stages
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As the AGC voltage increases, the gain of the
amplifier being controlled _______.
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As the AGC voltage increases, the gain of the
amplifier being controlled _______.
decreases
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What component makes it possible to vary the
frequency of the tuner and the frequency of the
local oscillator at the same time?
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What component makes it possible to vary the
frequency of the tuner and the frequency of the
local oscillator at the same time?
Ganged capacitor
83
Name the component that replaces the mechanical
variable capacitor in an electronically tuned
radio.
84
Name the component that replaces the mechanical
variable capacitor in an electronically tuned
radio.
Varactor or varicap diode
85
What is the range of frequencies received by a
standard AM broadcast receiver?
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What is the range of frequencies received by a
standard AM broadcast receiver?
535 kHz to 1605 kHz
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What is the range of frequencies produced by the
local oscillator in a standard AM broadcast
receiver?
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What is the range of frequencies produced by the
local oscillator in a standard AM broadcast
receiver?
540 kHz 455 kHz 995 kHz 1600 kHz 455 kHz
2055 kHz
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State two factors which must be considered by the
designer when selecting the IF frequency?
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Sate two factors which must be considered by the
designer when selecting the IF frequency?
Separation from the sum frequency Separation from
the image frequency
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What must the Single Sideband receiver do before
it can demodulate the signal?
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What must the Single Sideband receiver do before
it can demodulate the signal?
Put the carrier back
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What circuit in the Single Sideband receiver is
used to reproduce the carrier before demodulation?
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What circuit in the Single Sideband receiver is
used to reproduce the carrier before demodulation?
Beat Frequency Oscillator (BFO)
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Why must care be taken when troubleshooting a
tube type receiver?
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Why must care be taken when troubleshooting a
tube type receiver?
Lethal voltages are present.
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Why must care be taken when troubleshooting a
tube type receiver?
Lethal voltages are present.
98
Circle and label each stage.