Canadian Basic Qualification pool, section B-008-002

Subelement B-008

B-008

Section B-008-002

B-008-002-001

What devices would you install to reduce or eliminate interference to a home entertainment system from an HF transmitter?

A.
Metal oxide varistors
B.
Bypass inductors
Correct Answer
C.
Coils on ferrite cores
D.
Bypass resistors

B-008-002-001

A frequent cause of interference to home entertainment systems is that the long speaker leads act as antennas and bring radio energy into the audio amplifier stages, audio rectification ensues. Keeping the RF out of the audio circuitry can be achieved by winding the speaker leads on ferrite cores to form a choke (high inductive reactance at RF).

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

Tags: none

B-008-002-002

What should be done if a properly operating amateur radio station is the cause of interference to a nearby telephone?

A.
Make internal adjustments to the telephone equipment
B.
Stop transmitting whenever the telephone is in use
C.
Ground and shield the telephone distribution amplifier
Correct Answer
D.
Install a modular plug-in telephone RFI filter close to the telephone device

B-008-002-002

"RFI Filter" = Radio Frequency Interference filter. Much like home entertainment systems with their long speaker leads acting as antennas, wire-line telephones with cabling running through the house and streets can easily pick up RF energy. Filters installed at the telephone set usually solve the problem.

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

Tags: none

B-008-002-003

What sound is heard from a public address system if audio rectification of a nearby single-sideband transmission occurs?

A.
On-and-off humming or clicking
Correct Answer
B.
Distorted speech from the transmitter's signals
C.
A steady hum
D.
Clearly audible speech from the transmitter's signals

B-008-002-003

Much like home entertainment systems, the long speaker leads in a Public-Address sound system act as antennas and bring radio energy into the audio amplifier stages. Interfering SSB signals are heard as distorted speech in the sound system. Interfering CW signals are heard as on-and-off clicks or hum.

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-008-002-004

What sound is heard from a public address system if audio rectification of a nearby CW transmission occurs?

Correct Answer
A.
On-and-off humming or clicking
B.
Muffled, severely distorted speech
C.
A steady whistling
D.
Audible, possibly distorted speech

B-008-002-004

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

Tags: none

B-008-002-005

If an amateur radio transmission is heard in a device that contains no RF components, what type of interference is this?

A.
Front-end overload
B.
Intermodulation
Correct Answer
C.
Audio rectification
D.
Splatter

B-008-002-005

Audio rectification can be compared to a form of detection. A semiconductor circuit behaves like the detector in a receiver to retrieve the message from a radio signal. Typically, the circuit is exposed to a strong RF signal.

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

Tags: none

B-008-002-006

An amateur radio transmitter is being heard across the entire dial of a broadcast receiver. The receiver is most probably suffering from:

A.
harmonics interference
B.
poor image rejection
C.
splatter from the transmitter
Correct Answer
D.
audio rectification

B-008-002-006

Key words: ACROSS THE DIAL. This has to be a case of OVERLOAD. 'Intermodulation' and 'audio rectification' are two manifestations of overload. All other choices would not appear 'across the dial': an 'Harmonic' falls on a precise frequency, 'Splatter' is limited to a few kilohertz.

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

Tags: none

B-008-002-007

Your SSB HF transmissions are heard muffled on a sound system in the living room regardless of its volume setting. What causes this?

A.
Improper filtering in the transmitter
Correct Answer
B.
Audio rectification of strong signals
C.
Harmonics generated at the transmitter
D.
Lack of receiver selectivity

B-008-002-007

Key words: REGARDLESS OF ITS VOLUME SETTING. That clue reveals that the offending signal finds its way into the audio circuitry. Nothing needs to be wrong with the affected equipment or the transmitter. It is simply that the equipment is exposed to more radio energy that it can handle. 'Rectification' leads to 'detection': any semiconductor device may start acting like a diode and perform the two functions.

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

Tags: none

B-008-002-008

What device can be used to minimize the effect of RF pickup by audio wires connected to stereo speakers, intercom amplifiers, telephones, etc.?

A.
Surge suppressor
B.
Attenuator
C.
High-pass filter
Correct Answer
D.
Coil on ferrite core

B-008-002-008

Long wires act as antennas. The wires should be kept as short as possible. Winding speaker or telephone wires around a 'ferrite core' makes an inductor (a coil). Inductors oppose (inductive reactance) high frequency AC signals such as radio frequency. The 'ferrite core' makes for more inductance even with only a few turns of wire. Ferrite is a material with electromagnetic properties.

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

Tags: none

B-008-002-009

Stereo speaker leads often act as antennas to pick up RF signals. What is one method you can use to minimize this effect?

Correct Answer
A.
Shorten the leads
B.
Connect the speakers through audio attenuators
C.
Lengthen the leads
D.
Connect the speakers through series capacitors

B-008-002-009

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

Tags: none

B-008-002-010

One method of preventing RF from entering a stereo set through the speaker leads is to wrap each of the speaker leads:

Correct Answer
A.
around a ferrite core
B.
around a wooden dowel
C.
around an iron bar
D.
around a copper bar

B-008-002-010

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

Tags: none

B-008-002-011

Stereo amplifiers often have long leads that pick up transmitted signals because they act as:

A.
frequency discriminators
B.
parasitic elements
C.
resonant circuits
Correct Answer
D.
receiving antennas

B-008-002-011

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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