10
Electronics
Quarter 3 – Module 4:
Circuit Diagram and Layout of
an AM/FM Receiver
DIVISION OF ANGELES CITY
Electronics– Grade 10
Alternative Delivery Mode
Quarter 3 – Module 4: Circuit Diagram and Layout of an AM/FM receiver
First Edition, 2021
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Published by the Department of Education
Regional Director
:
May B. Eclar PhD, CESO V
OIC Asst. Regional Director
:
Rhoda T. Razon EdD, CESO V
Development Team of the Module
Writers: Arnel C. Perez, Ferdinand J. Soriano, Mark Albert T. Pineda
Editors: Marjorie D. Lacson, Nerissa N. Valdez, Eliza M. Roque
Reviewers: Gemima A. Estrabillo, Emily F. Sarmiento, Hermes P. Vargas,
Noel S. Reganit, Adrian P. Tamayo, Krislene Ida N. Mercado,
Jonathan Carrasco, Billy Ray B. Manuel, Marvin R. Leano,
Gemmarie G. Rivas
Illustrator: Lady Diane M. Bonifacio
Layout Artist: Lithos Sto. Domingo
Management Team: May B. Eclar PhD, CESO V
Rhoda T. Razon EdD, CESO V
Ma. Irelyn P. Tamayo PhD, CESE
Fernandina P. Otchengco PhD, CESE
Librada M. Rubio PhD
Ma. Editha R. Caparas EdD
Emily F. Sarmiento, PhD
Gemima A. Estrabillo, PhD
Rochella C. David
Printed in the Philippines by ___________________________
Department of Education – Region III- Division of Angeles CIty
Office Address:
Jesus St., Pulungbulu, Angeles City
Telefax:
(045) 322-5722; 322-4702; 888-0582; 887-6099
E-mail Address:
angeles.city@deped.gov.ph
10
Electronics
Quarter 3 – Module 4:
Circuit Diagram and Layout of
an AM/FM Receiver
Introductory Message
This Self-Learning Module (SLM) is prepared so that you, our dear learners,
can continue your studies and learn while at home. Activities, questions, directions,
exercises, and discussions are carefully stated for you to understand each lesson.
Each SLM is composed of different parts. Each part shall guide you step-bystep as you discover and understand the lesson prepared for you.
Pre-tests are provided to measure your prior knowledge on lessons in each
SLM. This will tell you if you need to proceed on completing this module or if you
need to ask your facilitator or your teacher’s assistance for better understanding of
the lesson. At the end of each module, you need to answer the post-test to self-check
your learning. Answer keys are provided for each activity and test. We trust that you
will be honest in using these.
In addition to the material in the main text, Notes to the Teacher are also
provided to our facilitators and parents for strategies and reminders on how they can
best help you on your home-based learning.
Please use this module with care. Do not put unnecessary marks on any part
of this SLM. Use a separate sheet of paper in answering the exercises and tests. And
read the instructions carefully before performing each task.
If you have any questions in using this SLM or any difficulty in answering the
tasks in this module, do not hesitate to consult your teacher or facilitator.
Thank you.
What I Need to Know
This module was designed and written with you in mind. It is here to help you
master the circuit diagram and layout of an AM/FM receiver. The scope of this
module permits it to be used in many different learning situations. The language
used recognizes the diverse vocabulary level of students. The lessons are arranged
to follow the standard sequence of the course. But the order in which you read them
can be changed to correspond with the textbook you are now using.
The module will cover the lesson:
●
Lesson 4 – Circuit Diagram and Layout of an AM/FM receiver
After going through this module, you are expected to:
● Interpret the diagram and layout of the components of an AM/FM receiver for
accurate circuit assembly.
1
What I Know
Direction: Choose the letter of the best answer.
1. What part of the FM receiver interprets the signal processed by the
demodulator?
a. Input transducer
c. Photodiode
b. Output transducer
d. Transistor
2. What do you call the component made of two wires wound around the core?
a. Antenna
c. Transducer
b. Oscillator
d. Zener diode
3. What part of the receiver prevents interfering signals that enter the radio
tuner?
a. Antenna
c. IF section
b. Detector
d. Mixer
4. What is the usual component found in the mixer?
a. Antenna
c. Photodiode
b. Mirror
d. Transistor
5. What component is usually involved in the IF section?
a. Capacitors
c. Resistors
b. Detector
d. Transformer
6. What is the other name of the demodulator?
a. Capacitors
b. Detector
c. Resistors
d. Transformer
7. What is the usual component found in the detector?
a. Crystal Diode
c. Transformer
b. Lead Resistor
d. Transistor
8. Which among the process involves the mixing of two different signals to
produce new ones?
a. Convolution
c. Heterodyne
b. Echo reaction
d. Oscillation
9. What component is used in making a tuning condenser?
a. Capacitors
c. Resistors
b. Detector
d. Transformer
10. Which receiver’s component is used to intercept and collect radio signals?
a. Antenna
c. Mixer
b. IF section
d. Detector
2
Lesson
1
Circuit Diagram and Layout
of an AM/FM Receiver
Radio wave acts as a carrier of information-bearing signals, and the
information may be encoded directly on the wave by periodically interrupting its
transmission or impressed on it by the process of modulation. When the radio waves
reach the receiving antenna, it induces electromotive force (emf) in it, which is very
small in magnitude and feeds to the radio receiver. Here in figure 1, the radio waves
that the antenna receives is amplified by the radio frequency (RF) amplifier, then the
process of demodulation extracts signals from them. The signal amplifies by audio
amplifiers and then feed to the speaker for reproduction into sound waves.
Source: https://kids.britannica.com/students/assembly/view53880
Figure 1. Radio waves reception and conversion.
3
What’s In
A radio receiver is the opposite of a radio transmitter. It uses an antenna to
capture radio waves, processes those waves to extract only those waves that vibrate
at the desired frequency, extracts the audio signals that add to those waves, amplifies
the audio signals, and finally plays them on a speaker. There were different
structures discussed in week 3 such as the tuner and audio detector. The table below
shows the list of the parts involved in the reception of radio waves.
To check the lessons that were taught last time, answer the table below by
writing each part of a radio receiver’s function.
Parts of a radio receiver
Function
Tuner
Audio Detector
Audio Amplifier
Reproducer
What’s New
In the transistor radio receiver set that we have at home, the radio tuner is a
section that intercepts and collects the radio signals coming from the radio
broadcasting or transmitting station. There are two types of radio tuners. One is the
amplitude modulation (AM) radio tuner, and the other is the frequency modulation
(FM) radio.
In amplitude modulation, the frequency of the signal is constant, but the
amplitude or height of the signal varies. On the other hand, in the frequency
modulation, the frequency of the signal varies, but the amplitude or height of the
signal is constant.
Activity 1. Guess What
DIRECTION: Read the statement carefully and identify the correct answer.
__________1. It intercepts and collects the radio signals coming from the radio
broadcasting or transmitting radio stations.
__________2. It selects which of the collected radio signals at the antenna should
enter the radio tuner.
4
__________3. It prevents the signal from radiating to other circuits in the radio tuner.
__________4. It mixes the signals coming from the antenna that tuned-in by the
tuning capacitor and the signals that come from the local oscillator.
__________5. This section of the radio tuner is like an electronic gate.
__________6. It is also called the demodulator. Its work is to detect and recover the
audio information from the radio signal received by the radio tuner.
__________7. This is found in transistor radio receivers that are made up of a coil of
small wires.
__________8-9. These are two wires wind around the iron core.
__________10. The part of the receiver that is also called as variable capacitor.
What is It
RADIO RECEIVER
AM Radio Parts and Functions
Antenna. The antenna’s function in the radio tuner is to intercept and collect
the radio signals coming from the radio broadcasting or transmitting radio station.
The antenna collects all the radio signals from the transmitting radio station. The
receiving antenna in transistor radio receivers is made of a coil of small wires. These
wires wound around the ferrite core. There are two wire windings around the ferrite
core. One winding is called the primary winding, while the other is called the
secondary winding. In figure 2, you will see the AM radio tuner Schematic Diagram.
5
Tuning Capacitor or Tuning Condenser. The tuning capacitor’s work is to
select which of the collected radio signals at the antenna should enter the radio
tuner. Only one radio signal should enter the radio tuner, and that radio signal is
the one selected or tuned-in by the tuning capacitor. The tuning capacitor is
composed of metal plates that are separated by the insulators. Tuning capacitors are
also called variable capacitors. The capacitance or capacity of the tuning capacitor
is varied or changed every time we turn its knob to select which radio signal from the
radio station should enter the radio tuner; the plates of the adjustable tuning
capacitor are called the rotor plates. The plates that are not adjustable is called the
stator plates.
Local Oscillator. The work of the local oscillator is to produce the oscillator
signal. This signal is called a local oscillator signal. The local oscillator is in the radio
receiver and is local to the radio receiver. There is also an oscillator in the radio
transmitting station, and this is called radiofrequency (RF) or radio carrier frequency
oscillator. The local oscillator is made of two small wires. These small wires are
wound around the adjustable ferrite core. One wire winding is called the primary
winding, and the other is called the secondary winding. The local oscillator is usually
enclosed in a metal shield to prevent the local oscillator signal from radiating to other
circuits in the radio tuner. To identify it, the top portion of the local oscillator is
usually painted red color.
Mixer-Converter Transistor. As the name implies, its function is to mix the
signals coming from the antenna. It is tuned in by the tuning capacitor, and the
signals come from the local oscillator. After mixing, these two signals are converted
to new signals known as the intermediate frequency (IF signal). The standard
frequency of the IF signals for amplitude modulation (AM) radio tuner is 455 kHz,
(Kilohertz), or 455,000 Hertz, (Hz). These are the same for all AM radio tuners. The
process of mixing two different signals to produce a new signal or signals is called
the heterodyne process or heterodyning process. This process is used in all radio
receivers, and that is why all radio receivers are often called superheterodyne radio
receivers.
Intermediate Frequency (IF) Section. The IF section of the radio tuner is like
an electronic gate. When the 455 kHz IF signal arrives, it automatically opens to
permit this 4bb kHz IF signal to pass through and enter the radio tuner. However,
when other signals whose frequency is not 455 KHz attempts to enter, the IF section
automatically blocks this signal. The IF section prevents interfering signals to enter
the radio tuner when it is tuned to one radio station with this action.
Typically, there are three intermediate frequency transformers (IFTs) used in
the IF section. Between the second IFT and third IFT is the second IF amplifier
transistor. However, although three IFTs were used and two IF amplifier transistors
in the IF section, their functions are the same; they prevent interference. The basic
construction of the IF transformers is the same. They are made of two small wires
wound around the adjustable ferrite core and enclosed in a metal shield. The
adjustable ferrite cores are adjusted during the aligning process of the radio tuner.
6
Detector. The detector is also called the demodulator. Its work is to detect and
recover the audio information from the radio signal received by the radio tuner. The
radio signal that comes from the radio station contains the audio information or
audio signal. This audio information is the equivalent of the radio announcer’s voice
or the voices that comes from the record being played at the radio station. When the
receiving antenna receives the radio signal, it contains this audio information, and it
is the detector that detects and recovers this audio information. The separated and
recovered audio information or signal is then fed to the audio amplifier where it is
amplified or strengthened sufficiently; the detector is usually made of a small crystal
diode. Below is the pictorial diagram of the receiver and its components.
Figure 3. Pictorial diagram of a radio receiver circuit and components
How the Radio Signal Flows in the Radio Tuner
We have seen the pre-emphasis network (High pass filter), which is present
before the FM modulator. It is used to improve the SNR of high-frequency audio
signals. Thus, in this FM receiver, the de-emphasis network (Low pass filter) is
included after the FM demodulator. This signal is passed to the audio amplifier to
increase the power level. Finally, we get the original sound signal from the
loudspeaker. Below is the block diagram of the FM signal receiver to overcome these
drawbacks.
Image Source: https://circuitdiagramimages.blogspot.com/2019/02/fm-transmitterand-receiver-block.html
Figure 4. Block diagram of a FM signal receiver
7
What’s More
Activity 2: NAME THAT SYMBOLS
Direction: Identify each electronic symbol found in AM Radio Receiver’s schematic
diagram by writing the names and the value of the components.
Example. Answer-Resistor 1,000,000 ohms
Example
1
2
3
625mW
http://whatis-electronics.blogspot.com/2010/08/fm-radio-reciever.html
4
5
Component
Value
1.
2.
3.
4.
5.
Assessment 2:
1. Where do you think the reception of radio waves start in the diagram? List down
the components involved.
2. How do L2-2.2µH, TR2, R3-1M, and C3-10nF work in the radio receiver system?
8
Activity 3: Stop, Think and Write
Direction: Write your insights on the importance of the circuit component in a FM
receiver through creative writing. A minimum of one hundred words and
a maximum of one hundred fifty words can be applied in this activity.
Features
Quality of
Writing
Grammar,
Usage &
Mechanics
4
Expert
The piece was
written in an
extraordinary
style and voice.
Very informative
and wellorganized
There were
spelling,
punctuation, or
grammatical
errors.
3
Accomplished
The piece was
written in an
interesting style
and voice.
Somewhat
informative and
organized
There were few
spelling and
punctuation errors,
minor grammatical
errors.
2
Capable
The piece had
little style or
voice.
Gives some new
information but
poorly
organized
A number of
spelling,
punctuation or
grammatical
errors.
1
Beginner
The piece had no
style or voice.
Gives no new
information and very
poorly organized
There were many
spelling,
punctuation, and
grammatical errors
that interfere with
the meaning.
Activity 4: Go with the flow
Direction: Fill out the missing parts of the FM radio receiver block diagram.
Assessment 4:
1. What is the role of the local oscillator in the block diagram?
2. How does the radio signal received by the antenna convert into sound in the
loudspeaker?
9
What I Have Learned
Direction: Let us summarize your insights by searching the words on the word pool
below.
WORD POOL
Guide Questions:
1. How do you describe the process of signal reception in the demodulator?
2. How do you describe the function of a transistor in the AM/FM receiver?
Rubric
1 point
2 points
3 points
4 points
5 points
Answer is
completely
incorrect, and
no support is
provided
Answer is correct
but there is no
support, OR the
answer is
incorrect but
there is some
correct support
Answer is
correct and
there is
some
support
Answer is
correct and
support needs
continuity
Answer is
correct and
the support is
fully
developed
10
What I Can Do
Direction: Complete the sentences by putting the correct word/s from the box.
Primary and secondary
Mixer-converter transistor
Ferrite core
Metal plates
Intercept and collect
Audio amplifier
Capacitance
RF Signal
FM receiver
Heterodyning
1. The ______________ of the tuning capacitor is varied or changed every time
we turn its knob to select which radio signal from the radio station should
enter the radio tuner.
2. Sensitivity is the capacity to detect an ____________ and demodulate it while
at the lowest power level.
3. The antenna’s function in the radio tuner is to _________________the radio
signals coming from the radio broadcasting or transmitting radio station.
4. The IF transformers are made of two small wires wound around the
adjustable _____________ and enclosed in a metal shield.
5. The _____________ is the whole unit that takes the modulated signal as
input and produces the original audio signal as an output.
6. A _______________________mixes the signals coming from the antenna.
7. A local oscillator is made from two wire winding which are called the
_______________________winding.
8. The process of mixing two different signals to produce a new signal or
signals is called the _____________.
9. The separated and recovered audio information generated by the detector
is then fed to the _____________ where it is amplified or strengthened
sufficiently.
10. The tuning capacitor is composed of ______________that are separated by
the insulators.
11
Assessment
Direction: Multiple Choice. Encircle the letter of the best answer.
1.
Which among the following best describes a tuning capacitor?
a. It selects the radio signals that should enter the radio tuner.
b. It has two wire windings around the ferrite core.
c. It mixes the signals coming from the antenna.
d. It produces the oscillating signal.
2. Which device in a signal receiver separates the audio information from the
received radio signals?
a. Capacitors
c. Resistors
b. Detector
d. Transformer
3. What is the standard frequency of the IF signals in an AM radio tuner?
a. 45 Hz
c. 455 kHz
b. 455 Hz
d. 455 MHz
4. What is the main structure of an IF transformer?
a. Wire wound around a soft iron core
b. An N and P type semiconductor
c. Two N-Type semiconductors
d. A single solenoid
5. What is found in between the separated conducting plate of a tuning
capacitor?
a. Charges
c. Metals
b. Insulators
d. Radio waves
6. How does the IF transistor function in the receiver?
a. They prevent signal interference
b. The allow the signal to pass
c. They filter radio waves
d. All of the above
7. What is the other term used for tuning capacitor?
a. Fixed capacitor
c. Polar capacitor
b. Lead capacitor
d. Variable capacitor
8. Which receiver component usually strengthens the signal that is recovered?
a. Amplifier
c. Detector
b. Capacitor
d. Diode
9. What is produced in the local oscillator in the radio transmitting station?
a. Electric surge
c. Linear wave
b. Interference
d. Radio Frequency
10. What do you call the capacity of detecting an RF signal and demodulating it?
a. Sensitivity
c. Separability
b. Selectivity
d. Saturability
12
Additional Activity
Direction: Write the correct name of each picture.
1.
2.
3.
4.
5.
13
What I Know
1. c
6. c
2. a
7. d
3. a
8. c
4. d
9. d
5. d
10. c
What's New
Act ivity 1
1. Antenna
2. Tuner
3. Local Oscillator
4. Mixer-Converter Transistor
5. Intermediate Frequency
6. Detector
7. Antenna
8. Primary Winding
9. Secondary Winding
10. Tuning Capacitor
What’s More
Act ivity 4
1. RF amplifier
2. Mixer
3. Limiter
4. De-emphasis Network
5. AF and power amplifiers
Assessment 4:
1. It produces oscillating signal that is
local to the receiver and prevents radiating
signal to other circuit of the receiver.
2. The signal that is received by the
antenna is processed by the demodulator
which extracts the message then
processed by the amplifier to make the
signal stronger that is converted to sound.
Assessment
1. a
2. b
3. c
4. a
5. b
6. a
7. d
8. a
9. d
10. a
14
What’s In
Answer are found in module 3
What’s More
Act ivity 2
1. Resistor-10k Ohms
2. Resistor-4.7k Ohms
3. Capacitor-100 microfarad
4. Inductor-2.2 microhenry
5. Transistor
Assessment 2
1.It starts in L1 by using the VC1 and VC2 to be
processed by TR1
2. L2-2.2µHit acts as an antenna that receives the
signal while the TR2 serves as an amplifier. The
R3-1M impedes flow of current while the C3-10nF
stores energy that is released in the circuit.
Act ivity 3
Answer may vary
What I have Learned
Answer may vary
What can I do?
1. Capacitance
2. RF Signal
3. Intercept and collect
4. Ferrite core
5. FM receiver
6. Mixer-converter transistor
7. Primary and secondary
8. Heterodyning
9. Audio amplifier
10. Metal plates
Additional Activity
1. Antenna
2. Tuning Capacitor
3. Diode
4. Local Oscillator
5. Mixer-Converter transistor
Answer Key
References
AM/FM Radio system December 25, 2020 https://tinyurl.com/yywxsxof
DIY FM Receiver, Accessed December 25, 2020 https://tinyurl.com/y5ks2wpk
How does a radio work? December 25, 2020 https://tinyurl.com/y7zemz3e
Radio FM receiver, Accessed December 24, 2020. https://tinyurl.com/y47trwhg
Radio AM receiver, Accessed December 24, 2020. https://tinyurl.com/yxzfykht
15
For inquiries or feedback, please write or call:
Department of Education – Region III- Schools Division of Angeles City
Jesus St., Pulungbulu, Angeles City, Pampanga, Philippines 2009
Telefax: (045) 322-5722; 322-4702; 888-0582; 887-6099
Email Address: angeles.city@deped.gov.ph