Download Module 7

Technician License Course
Chapter 3
Types of Radios and Radio Circuits
Module 7
The Basic Radio Station
Basic Station Organization
• Station Equipment
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Receiver
Transmitter
T R Switch
Antenna
Power Supply
• Accessory Station Equipment
Microphones, CW Keys, etc.
Well equipped station
Transmit/Receive (TR) Switch
• If the station antenna is shared between the
transmitter and receiver, the TR switch allows the
antenna to be switched to the transmitter when
sending and to the receiver when receiving.
– In a transceiver, this TR switch is inside the unit and
requires no attention by the operator.
What Happens During Radio
Communication?
• Transmitting (sending a signal):
– Information (voice, data, video, commands,
etc.) is converted to electronic form.
– The information in electronic form is attached
or embedded on a radio wave (a carrier).
– The radio wave is sent out from the station
antenna into space.
What Happens During Radio
Communication?
• Receiving end:
– The radio wave (carrier) with the information is
intercepted by the receiving station antenna.
– The receiver extracts the information from the
carrier wave.
– The information is then presented to the user in
a format that can be understood (sound, picture,
words on a computer screen, response to a
command).
What Happens During Radio
Communication?
• This sounds pretty simple, but it in reality is pretty
complex.
• This complexity is one thing that makes ham radio
fun…learning all about how radios work.
• Don’t be intimidated. You will be required to only
know the basics, but you can learn as much about
the “art and science” of radio as you want.
Simple CW Transmitter
Block Diagram
Receiver Circuits
• Oscillators produce signals at a desired
frequency.
• Mixers combine signals, and produce both the
sum and difference of the input signals.
• Filters remove unwanted frequencies or
signals.
• Pre –amplifiers and amplifiers increase signal
levels.
Receiver Design
• It is always a challenge for receiver designers
to balance the competing traits of selectivity
and sensitivity. Selectivity expresses how well
a receiver rejects adjacent signals. Sensitivity
expresses how faint a signal can be detected.
• Product detectors are used in receivers for SSB
and CW signals to extract the modulation.
• Frequency discriminators are used in receivers
for FM signals to extract the modulation.
Transmitter Circuits
• A modulator combines audio and RF signals.
• A power amplifier increases the level of the
modulated signal. Power amplifiers can be
added externally to increase the transmitted
signal strength.
• A transverter is a device that converts a carrier
frequency to another frequency. ( Eg: 28 Mhz
to 220Mhz )
Receiver Block Diagram
RF Input
Mixer
Local
Oscillator
(Tuner)
Filter
Detector
9-Volts DC
Conditioner
Receiver Block Diagram w/
Preamp
Pre-amplifier
RF Input
Mixer
Filter
Local
Oscillator
(Tuner)
Detector
9-Volts DC
Conditioner
A pre-amplifier can be inserted between the
antenna and receiver input to increase
receiver sensitivity to weak signals.
Superheterodyne Receiver
• One of the most widely used AM, SSB, and CW
receiver designs is the superheterodyne receiver. The
incoming signal is mixed with a local oscillator to
produce an intermediate frequency, which is sent to a
product detector for mixing with a beat frequency
oscillator. The resulting audio frequency is
amplified, and comes out the speaker.
• Single conversion superhet receivers use a single IF
stage. Dual conversion superhet receivers use two IF
stages.
The Superheterodyne Receiver
Block Diagram
FM Receivers
• FM receivers are designed to detect the
frequency variations on the carrier that are
produced by this type of modulation.
• A frequency discriminator detects the variation
from the carrier frequency.
• FM signals are less affected by natural noise
than AM signals.
The FM Receiver
Block Diagram
What is the function of a product detector?
(T7A01)
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•
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A.
B.
C.
D.
Detect phase modulated signals
Demodulate FM signals
Detect CW and SSB signals
Combine speech and RF signals
What is the function of a product detector?
(T7A01)
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•
•
•
A.
B.
C.
D.
Detect phase modulated signals
Demodulate FM signals
Detect CW and SSB signals
Combine speech and RF signals
What type of receiver is shown in Figure T6?
(T7A02)
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•
A.
B.
C.
D.
Direct conversion
Super-regenerative
Single-conversion superheterodyne
Dual-conversion superheterodyne
What type of receiver is shown in Figure T6?
(T7A02)
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•
•
•
A.
B.
C.
D.
Direct conversion
Super-regenerative
Single-conversion superheterodyne
Dual-conversion superheterodyne
What is the function of a mixer in a
superheterodyne receiver? (T7A03)
• A. To reject signals outside of the desired
passband
• B. To combine signals from several stations
together
• C. To shift the incoming signal to an
intermediate frequency
• D. To connect the receiver with an auxiliary
device, such as a TNC
What is the function of a mixer in a
superheterodyne receiver? (T7A03)
• A. To reject signals outside of the desired
passband
• B. To combine signals from several stations
together
• C. To shift the incoming signal to an
intermediate frequency
• D. To connect the receiver with an auxiliary
device, such as a TNC
What circuit is pictured in Figure T7, if block
1 is a frequency discriminator? (T7A04)
•
•
•
•
A.
B.
C.
D.
A double-conversion receiver
A regenerative receiver
A superheterodyne receiver
An FM receiver
What circuit is pictured in Figure T7, if block
1 is a frequency discriminator? (T7A04)
•
•
•
•
A.
B.
C.
D.
A double-conversion receiver
A regenerative receiver
A superheterodyne receiver
An FM receiver
What is the function of block 1 if figure T4 is
a simple CW transmitter? (T7A05)
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•
•
•
A.
B.
C.
D.
Reactance modulator
Product detector
Low-pass filter
Oscillator
What is the function of block 1 if figure T4 is
a simple CW transmitter? (T7A05)
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•
•
•
A.
B.
C.
D.
Reactance modulator
Product detector
Low-pass filter
Oscillator
What device takes the output of a lowpowered 28 MHz SSB exciter and produces
a 222 MHz output signal? (T7A06)
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•
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•
A.
B.
C.
D.
High-pass filter
Low-pass filter
Transverter
Phase converter
What device takes the output of a lowpowered 28 MHz SSB exciter and produces
a 222 MHz output signal? (T7A06)
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•
A.
B.
C.
D.
High-pass filter
Low-pass filter
Transverter
Phase converter
If figure T5 represents a transceiver in which block
1 is the transmitter portion and block 3 is the
receiver portion, what is the function of block 2?
(T7A07)
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•
•
A.
B.
C.
D.
A balanced modulator
A transmit-receive switch
A power amplifier
A high-pass filter
If figure T5 represents a transceiver in which block
1 is the transmitter portion and block 3 is the
receiver portion, what is the function of block 2?
(T7A07)
•
•
•
•
A.
B.
C.
D.
A balanced modulator
A transmit-receive switch
A power amplifier
A high-pass filter
Which of the following circuits combines a
speech signal and an RF carrier? (T7A08)
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•
•
•
A.
B.
C.
D.
Beat frequency oscillator
Discriminator
Modulator
Noise blanker
Which of the following circuits combines a
speech signal and an RF carrier? (T7A08)
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•
•
•
A.
B.
C.
D.
Beat frequency oscillator
Discriminator
Modulator
Noise blanker
Which of the following devices is most useful
for VHF weak-signal communication?
(T7A09)
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A.
B.
C.
D.
A quarter-wave vertical antenna
A multi-mode VHF transceiver
An omni-directional antenna
A mobile VHF FM transceiver
Which of the following devices is most useful
for VHF weak-signal communication?
(T7A09)
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•
A.
B.
C.
D.
A quarter-wave vertical antenna
A multi-mode VHF transceiver
An omni-directional antenna
A mobile VHF FM transceiver
What device increases the low-power output
from a handheld transceiver? (T7A10)
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A.
B.
C.
D.
A voltage divider
An RF power amplifier
An impedance network
A voltage regulator
What device increases the low-power output
from a handheld transceiver? (T7A10)
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A.
B.
C.
D.
A voltage divider
An RF power amplifier
An impedance network
A voltage regulator
Which of the following circuits demodulates
FM signals? (T7A11)
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A.
B.
C.
D.
Limiter
Discriminator
Product detector
Phase inverter
Which of the following circuits demodulates
FM signals? (T7A11)
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A.
B.
C.
D.
Limiter
Discriminator
Product detector
Phase inverter
Which term describes the ability of a
receiver to discriminate between multiple
signals? (T7A12)
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•
A.
B.
C.
D.
Tuning rate
Sensitivity
Selectivity
Noise floor
Which term describes the ability of a
receiver to discriminate between multiple
signals? (T7A12)
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•
•
•
A.
B.
C.
D.
Tuning rate
Sensitivity
Selectivity
Noise floor
Where is an RF preamplifier installed?
(T7A13)
• A. Between the antenna and receiver
• B. At the output of the transmitter’s power
amplifier
• C. Between a transmitter and antenna
tuner
• D. At the receiver’s audio output
Where is an RF preamplifier installed?
(T7A13)
• A. Between the antenna and receiver
• B. At the output of the transmitter’s power
amplifier
• C. Between a transmitter and antenna
tuner
• D. At the receiver’s audio output