Technician License Course Chapter 3 Types of Radios and Radio Circuits

1
Technician License CourseChapter 3 Types of
Radios and Radio Circuits
Module 7
2
The Basic Radio Station
3
Basic Station Organization

• Station Equipment
• Receiver
• Transmitter
• T R Switch
• Antenna
• Power Supply
• Accessory Station Equipment
• Microphones, CW Keys, etc.

4
Well equipped station
5
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.

6
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.

7
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).

8
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
  funlearning all about how radios work.
• Dont 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.

9
Simple CW Transmitter Block Diagram
10
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.

11
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.

12
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 )

13
Receiver Block Diagram

14
Receiver Block Diagram w/ Preamp

Pre-amplifier
A pre-amplifier can be inserted between the
antenna and receiver input to increase receiver
sensitivity to weak signals.
15
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.

16
The Superheterodyne ReceiverBlock Diagram
17
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.

18
The FM ReceiverBlock Diagram
19
What is the function of a product detector?
(T7A01)

• A. Detect phase modulated signals
• B. Demodulate FM signals
• C. Detect CW and SSB signals
• D. Combine speech and RF signals

20
What is the function of a product detector?
(T7A01)

• A. Detect phase modulated signals
• B. Demodulate FM signals
• C. Detect CW and SSB signals
• D. Combine speech and RF signals

21
What type of receiver is shown in Figure T6?
(T7A02)

• A. Direct conversion
• B. Super-regenerative
• C. Single-conversion superheterodyne
• D. Dual-conversion superheterodyne

22
What type of receiver is shown in Figure T6?
(T7A02)

• A. Direct conversion
• B. Super-regenerative
• C. Single-conversion superheterodyne
• D. Dual-conversion superheterodyne

23
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

24
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

25
What circuit is pictured in Figure T7, if block 1
is a frequency discriminator? (T7A04)

• A. A double-conversion receiver
• B. A regenerative receiver
• C. A superheterodyne receiver
• D. An FM receiver

26
What circuit is pictured in Figure T7, if block 1
is a frequency discriminator? (T7A04)

• A. A double-conversion receiver
• B. A regenerative receiver
• C. A superheterodyne receiver
• D. An FM receiver

27
What is the function of block 1 if figure T4 is a
simple CW transmitter? (T7A05)

• A. Reactance modulator
• B. Product detector
• C. Low-pass filter
• D. Oscillator

28
What is the function of block 1 if figure T4 is a
simple CW transmitter? (T7A05)

• A. Reactance modulator
• B. Product detector
• C. Low-pass filter
• D. Oscillator

29
What device takes the output of a low-powered 28
MHz SSB exciter and produces a 222 MHz output
signal? (T7A06)

• A. High-pass filter
• B. Low-pass filter
• C. Transverter
• D. Phase converter

30
What device takes the output of a low-powered 28
MHz SSB exciter and produces a 222 MHz output
signal? (T7A06)

• A. High-pass filter
• B. Low-pass filter
• C. Transverter
• D. Phase converter

31
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. A balanced modulator
• B. A transmit-receive switch
• C. A power amplifier
• D. A high-pass filter

32
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. A balanced modulator
• B. A transmit-receive switch
• C. A power amplifier
• D. A high-pass filter

33
Which of the following circuits combines a speech
signal and an RF carrier? (T7A08)

• A. Beat frequency oscillator
• B. Discriminator
• C. Modulator
• D. Noise blanker

34
Which of the following circuits combines a speech
signal and an RF carrier? (T7A08)

• A. Beat frequency oscillator
• B. Discriminator
• C. Modulator
• D. Noise blanker

35
Which of the following devices is most useful for
VHF weak-signal communication? (T7A09)

• A. A quarter-wave vertical antenna
• B. A multi-mode VHF transceiver
• C. An omni-directional antenna
• D. A mobile VHF FM transceiver

36
Which of the following devices is most useful for
VHF weak-signal communication? (T7A09)

• A. A quarter-wave vertical antenna
• B. A multi-mode VHF transceiver
• C. An omni-directional antenna
• D. A mobile VHF FM transceiver

37
What device increases the low-power output from a
handheld transceiver? (T7A10)

• A. A voltage divider
• B. An RF power amplifier
• C. An impedance network
• D. A voltage regulator

38
What device increases the low-power output from a
handheld transceiver? (T7A10)

• A. A voltage divider
• B. An RF power amplifier
• C. An impedance network
• D. A voltage regulator

39
Which of the following circuits demodulates FM
signals? (T7A11)

• A. Limiter
• B. Discriminator
• C. Product detector
• D. Phase inverter

40
Which of the following circuits demodulates FM
signals? (T7A11)

• A. Limiter
• B. Discriminator
• C. Product detector
• D. Phase inverter

41
Which term describes the ability of a receiver to
discriminate between multiple signals? (T7A12)

• A. Tuning rate
• B. Sensitivity
• C. Selectivity
• D. Noise floor

42
Which term describes the ability of a receiver to
discriminate between multiple signals? (T7A12)

• A. Tuning rate
• B. Sensitivity
• C. Selectivity
• D. Noise floor

43
Where is an RF preamplifier installed? (T7A13)

• A. Between the antenna and receiver
• B. At the output of the transmitters power
  amplifier
• C. Between a transmitter and antenna tuner
• D. At the receivers audio output

44
Where is an RF preamplifier installed? (T7A13)

• A. Between the antenna and receiver
• B. At the output of the transmitters power
  amplifier
• C. Between a transmitter and antenna tuner
• D. At the receivers audio output