Canadian Basic Qualification pool, section B-003-012

Subelement B-003

B-003

Section B-003-012

B-003-012-001

What may happen if an SSB transmitter is operated with the microphone gain set too high?

A.
It may cause interference to other stations operating on lower bands
B.
It may cause digital interference to computer equipment
C.
It may cause harmonic interference on higher bands
Correct Answer
D.
It may interfere with other stations operating near its frequency

B-003-012-001

Key words: MICROPHONE GAIN SET TOO HIGH. This leads to 'overmodulation' evidenced by distorted speech plus using excessive bandwidth on the air (splatter) which interferes 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-003-012-002

What may happen if an SSB transmitter is operated with too much speech processing?

A.
It may cause interference to other stations operating on a higher frequency band
B.
It may cause insufficient modulation of the carrier
C.
It may cause digital interference to computer equipment
Correct Answer
D.
It may cause audio distortion or splatter interference to other stations operating near its frequency

B-003-012-002

Key words: TOO MUCH SPEECH PROCESSING. 'Speech processing' is raising the average amplitude of the audio input from the microphone closer to an acceptable peak value: i.e., make every passage of the spoken words equally loud. Too much speech processing leads to distortion and possibly driving the linear power amplifier with too large a signal (overdriving). This leads to 'overmodulation' evidenced by distorted speech plus occupying excessive bandwidth on the air (splatter), which interferes 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-003-012-003

What is the term for the average power during one RF cycle, at the crest of the modulation envelope?

A.
RMS power
Correct Answer
B.
Peak envelope power
C.
Peak transmitter input power
D.
Average radio frequency power

B-003-012-003

Key word: ENVELOPE. PEP -- Peak Envelope Power ( a specification for SSB transmitters ): the average power at the output of a transmitter during one cycle at a modulation peak.

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

Tags: none

B-003-012-004

What is the usual bandwidth of an amateur radio single-sideband signal?

A.
Between 3 kHz and 6 kHz
Correct Answer
B.
Between 2 kHz and 3 kHz
C.
1 kHz
D.
2 kHz

B-003-012-004

By transposing the voice signal into the radio spectrum, the SSB transmitter manages to only use the approximate bandwidth of the original modulation ( speech frequencies important for communications span 300 hertz to 3000 hertz, a bandwidth of 2700 hertz ). SSB uses half the bandwidth of AM.

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

Tags: none

B-003-012-005

Why does the power amplifier of the SSB transmitter need to be linear?

A.
Hum and noise are reduced
B.
Power output variations due to voice peaks are reduced
Correct Answer
C.
Voice is unintelligible when amplified by a non-linear amplifier
D.
Power demand on the power supply is regulated

B-003-012-005

Single sideband is a form of amplitude modulation. Excessive distortion would render the message incomprehensible.

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

Tags: none

B-003-012-006

What is one advantage of carrier suppression in a double sideband voice transmission?

A.
Only half the bandwidth is needed for the same information content
B.
Simpler equipment can be used to receive a double sideband suppressed carrier signal
C.
Greater modulation percentage is obtainable with lower distortion
Correct Answer
D.
More of the output power can be put into the sidebands

B-003-012-006

Plain AM (Amplitude Modulation) produces a radio carrier, an upper sideband and a lower sideband. The sidebands are the ever-changing sum and differences in the modulating frequency (follows voice) and the carrier frequency (set at the operating frequency). The carrier by itself does NOT convey information. The message is in the sidebands. Suppressing the carrier permits using the full capacity of the Power Amplifier for the sidebands. Note: Suppressing the carrier an one sideband yields Single Sideband.

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

Tags: none

B-003-012-007

What does overmodulation do to a single-sideband signal?

A.
It occupies less bandwidth and has a poor high frequency response
Correct Answer
B.
It becomes distorted and occupies more bandwidth
C.
It has higher fidelity and an improved signal-to-noise ratio
D.
It increases the range of your signal

B-003-012-007

'Overmodulation' results in distorted speech plus using 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-003-012-008

How should the microphone gain control be adjusted for voice operation on a single-sideband transmitter?

A.
For 100% frequency deviation on voice peaks
Correct Answer
B.
Such that the maximum range on the ALC meter is never exceeded on voice peaks
C.
For full deflection of the ALC meter
D.
For a dip in the drain or collector current

B-003-012-008

Your owner's manual will say what reading is acceptable on the ALC meter. The automatic level control is a feedback circuit from the power amplifier to an earlier amplifier stage which seeks to avoid overdriving the transmitter with too much audio. When the ALC acts, it is a corrective action. An infrequent ALC action on modulation peaks indicates that there is no overdriving. If the ALC needed to intervene constantly, this would indicate that the operator is trying to feed too much audio through the transmitter.

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

Tags: none

B-003-012-009

The purpose of a balanced modulator in an SSB transmitter is to:

Correct Answer
A.
suppress the carrier and pass the two sidebands
B.
suppress the carrier and pass one sideband
C.
make sure that the carrier and both sidebands are 180 degrees out of phase
D.
ensure that the percentage of modulation is kept constant

B-003-012-009

The SSB Transmitter block diagram: The balanced modulator takes in two signals: a fixed frequency from an RF Oscillator and the microphone signal after it has passed through a speech amplifier. The balanced modulator produces a double-sideband suppressed-carrier signal. After the balanced modulator, a filter selects the desired sideband. This SSB signal is mixed with a variable frequency oscillator (VFO) signal by a mixer. Out of the mixer, the SSB signal is now at the operating frequency and is taken through a power amplifier. In the case of the SSB transmitter, this final power amplifier must be linear (distortion free).

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

Tags: none

B-003-012-010

Your SSB transmitter is set to operate lower sideband at 7100 kHz. With a single 1000 Hz tone as modulation, at which frequency is RF transmitted?

A.
7101 kHz
B.
6100 kHz
Correct Answer
C.
7099 kHz
D.
8100 kHz

B-003-012-010

In Amplitude Modulation, the position, along the radio spectrum, of a 'side frequency' within a sideband is the sum (or difference) of the modulating frequency and carrier frequency. The statement is also true with Single Sideband (SSB) where the carrier has been suppressed: the position of a 'side frequency' only has meaning in relation to the position of the phantom carrier. Suitable demodulation at the receiving end supposes that the "carrier is reinserted" so that each side frequency (a great number of which form a sideband) can be rendered as an exact audio frequency.

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

Tags: none

B-003-012-011

The automatic level control (ALC) in an SSB transmitter:

A.
reduces transmitter audio feedback
B.
reduces system noise
Correct Answer
C.
limits the input audio peaks so that the transmitter is not overdriven
D.
increases the occupied bandwidth

B-003-012-011

Your owner's manual will say what reading is acceptable on the ALC meter. The automatic level control is a feedback circuit from the power amplifier to an earlier amplifier stage, which seeks to avoid overdriving the transmitter with too much audio. When the ALC acts, it is a corrective action. An infrequent ALC action on modulation peaks indicates that there is no overdriving. If the ALC needed to intervene constantly, this would indicate that the operator is trying to feed too much audio through the transmitter.

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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