Canadian Basic Qualification pool, section B-003-015

Subelement B-003

B-003

Section B-003-015

B-003-015-001

Why can a modern digital radio system transmit voice and images, not just data?

A.
Digital protocols can fall back to analog as needed
B.
Modern transceivers have the necessary high efficiency amplifiers
C.
Digital signals are continuously variable signals
Correct Answer
D.
Any analog information can be converted to digital data

B-003-015-001

Once digitized, voice and images become data (a series of numbers) that a digital system is designed to transmit.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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B-003-015-002

What is the fundamental difference between digital and analog data?

A.
Digital data represents information as a continuously variable quantity
B.
Digital data requires complex waveforms for transmission
C.
Digital data easily translates into digital signals
Correct Answer
D.
Digital data is encoded as discrete pre-agreed values

B-003-015-002

Digital data represents any information as numbers and their interpretation must be clearly defined. Analog data can take varying values within a given range.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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B-003-015-003

What is the function of a digipeater?

Correct Answer
A.
To receive digital data and retransmit data marked for retransmission
B.
To receive analog FM, convert to digital data and retransmit
C.
To receive digital data and export to the internet
D.
To receive digital data, convert to analog FM and retransmit

B-003-015-003

A 'Digipeater' (contraction of 'digital repeater') only repeats packets specifically addressed for routing through that digipeater: i.e., marked with its call sign. Unlike duplex voice repeaters using two frequencies, the digipeater receives, temporarily stores and retransmits the data packets on a single frequency.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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B-003-015-004

What does "network" mean in packet radio?

A.
The connections on terminal-node controllers
B.
The programming in a terminal-node controller that rejects other callers if a station is already connected
Correct Answer
C.
A way of connecting packet-radio stations so data can be sent over long distances
D.
A way of connecting terminal-node controllers by telephone so data can be sent over long distances

B-003-015-004

In packet radio operation, a 'network' is a succession of digipeaters (or normal packet stations, which can also 'digipeat') used to connect to a station normally not within range of the originating station.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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B-003-015-005

Why can dozens of FT8 communications occur simultaneously in the space needed for one single-sideband transmission?

A.
Formatting of the messages into packets
B.
Message structure with limited contact information
C.
Time interleaving of the transmissions
Correct Answer
D.
Narrow bandwidth of an FT8 signal

B-003-015-005

A single FT8 signal occupies a bandwidth of about 50 Hz, far less than an SSB signal that occupies 2 to 3 kHz.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

B-003-015-006

Which of these modes can work at the lowest signal-to-noise ratio as measured in a 2500 Hz bandwidth?

Correct Answer
A.
FT8
B.
PSK31
C.
CW
D.
RTTY

B-003-015-006

FT8 is by design a weak-signal mode. Sophisticated digital signal processing allows it to dig signals out of the noise.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

B-003-015-007

When selecting an RTTY transmitting frequency, what minimum frequency separation from a contact in progress should you allow (centre to centre) to minimize interference?

A.
50 Hz to 100 Hz
B.
6 kHz to 10 kHz
Correct Answer
C.
250 Hz to 500 Hz
D.
3 kHz to 5 kHz

B-003-015-007

In order of bandwidth requirements: CW = about 100 Hz, RTTY = about 600 Hz, AM = 6 kHz, SSB = 2 to 3 kHz, FM = 10 to 20 kHz. Minimum frequency separation: CW = 150 to 500 Hz, RTTY = 250 to 500 Hz, SSB = 3 kHz to 5 kHz. [ The 'Mark' and 'Space' states are represented by two discrete frequencies, normally 170 Hz apart from one another. ]

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

B-003-015-008

When using a digital mode based on a computer sound card, how can you verify that the transmit audio level is NOT excessive?

Correct Answer
A.
Ask a local station to confirm your signal is free of splatter
B.
Verify that the automatic level control (ALC) is actively limiting every transmission
C.
Ask a local station to confirm your signal can be successfully decoded
D.
Ensure your transmitter's audio compression is set to maximum

B-003-015-008

Overmodulation (SSB) results in excessive bandwidth on the air (splatter) and interfering with stations using adjacent frequencies ('out-of-channel emissions').

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

B-003-015-009

What feature of packet radio makes it especially useful for emergency communications?

A.
Packet functionality is included in most modern radios
B.
Capable of simultaneous voice, image and data transmission
Correct Answer
C.
Reliable messaging (guaranteed delivery or notification of failure)
D.
Encrypted signals prevent eavesdropping

B-003-015-009

The protocol used in packet radio to deliver a message to a specific station includes an acknowledgement upon error-free reception of each information block.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

B-003-015-010

A digital protocol implements automatic repeat request (ARQ). What does it permit?

A.
Error detection
B.
Automatic link establishment
Correct Answer
C.
Error correction
D.
Unattended operation

B-003-015-010

When two stations are communicating by radio in a mode including "automatic repeat request", the receiving station must confirm the correct reception of each information block or request a retransmission.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

B-003-015-011

With a digital communication mode based on a computer sound card, what is the result of feeding excessive audio into the transmitter?

A.
Higher signal-to-noise ratio
B.
Power amplifier overheating
C.
Lower error rate
Correct Answer
D.
Splatter or out-of-channel emissions

B-003-015-011

Overmodulation (SSB) results in excessive bandwidth on the air (splatter) and interfering with stations using adjacent frequencies ('out-of-channel emissions').

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

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