Canadian Basic Qualification pool, section B-003-019

Subelement B-003

B-003

Section B-003-019

B-003-019-001

For best protection from electrical shock, what should be grounded in your station?

Correct Answer
A.
All station equipment
B.
The power supply primary
C.
The AC power line
D.
The transmission line

B-003-019-001

An external ground connection on each cabinet serves as a backup to the normal electrical outlet ground ( the 'green' wire in a three-lead power cord ).

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-003-019-002

Established practice demands that all ground electrodes be bonded together with heavy conductors. What protection does this provide in case of a lightning strike?

A.
Establishes a ground (reference) plane at the station
B.
Drains static electricity on a continuous basis
C.
Reduces induced current by adding impedance
Correct Answer
D.
Prevents voltage differences between devices

B-003-019-002

A 'metallic cold water pipe' normally offers the most direct solid conduction to Earth ground.

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-003-019-003

Why should you never use a fuse with a higher current rating than specified?

A.
Voltage delivered to the circuit would be limited
B.
The fuse may open during normal operation
C.
A low current circuit may not function properly
Correct Answer
D.
A fault may cause permanent damage, including a fire

B-003-019-003

The fuse rating recommended by a manufacturer takes into account the maximum current that the weakest part of a circuit can tolerate (the famed weakest link).

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-003-019-004

Which of these materials is best for a ground rod driven into the earth?

A.
Fibreglass
B.
Hard plastic
C.
Iron or steel
Correct Answer
D.
Copper-clad steel

B-003-019-004

'Copper-Clad' ( steel core, copper plating ) offers rigidity (when hammering the rod into the ground) and conductivity (for best ground connection).

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-003-019-005

You need to work on a power supply that has been taken offline. What is the first thing you should do once the cabinet is open?

A.
Short the AC input leads together
Correct Answer
B.
Discharge the filter capacitors
C.
Bond the chassis to ground
D.
Place the unit on an insulating mat

B-003-019-005

While a bleeder resistor should be wired across the filter to drain the energy stored in the capacitors, it could be missing or defective. It is safest to verify that no electric charge remains before sticking fingers or tools inside the power supply.

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-003-019-006

Where should the green wire in a three-wire AC line cord be connected in a power supply?

A.
To the fuse
Correct Answer
B.
To the chassis
C.
To the "hot" side of the power switch
D.
To the white wire

B-003-019-006

The 'green wire' in a three-wire AC line cord is a ground connection. Securing the 'green wire' to the chassis (and outside cabinet) keeps the chassis at ground potential if a fault ever caused the 'live' side (120 volts) of the AC line to contact the chassis.

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-003-019-007

Your third-floor station has a ground wire running 10 metres down to a ground rod. You get an RF burn when you touch your HF transceiver while transmitting. What is the likely cause?

A.
The ground connection of the wall outlet is defective
B.
The gauge of the ground wire used is insufficient
Correct Answer
C.
The ground wire has high impedance on your operating frequency
D.
The transmitting antenna is not the correct wavelength

B-003-019-007

Key word: 10 METRES. RF 'hot spots' and RF 'burns' are symptoms of 'Stray RF'. This is relatively long in comparison with some of the wavelengths in the HF (High Frequency) spectrum. For example, 10 metres is a quarter wavelength on the 40-metre band. A wire this long looks like an antenna and will not provide a low impedance ground connection necessary to evacuate 'Stray RF'.

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-003-019-008

You are using an HF off-centre-fed (OCF) unbalanced antenna. When you transmit on SSB, distorted audio and noise are heard from an outboard amplified speaker. What device could you install in the transmission line to mitigate this problem?

A.
An antenna tuner
B.
A surge suppressor
Correct Answer
C.
A common-mode choke
D.
A low-pass filter

B-003-019-008

Key words: OFF-CENTRE-FED. Any lack of symetry in the antenna system can lead to stray RF propagating along the transmission line. The common-mode choke impedes that flow.

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

Tags: none

B-003-019-009

What is a safe method to discharge power supply filter capacitors?

A.
Allow time for bleeder resistors to discharge the capacitors
Correct Answer
B.
Use an insulated shorting stick with an inline resistor
C.
Use an insulated wire with alligator clips on each end
D.
Use a long screwdriver with an insulated handle

B-003-019-009

The 'shorting stick' with an inline resistor to ground limits sparking and allows for a controlled discharge. Waiting for the bleeder resistor to do its job is the worst idea, it might be defective.

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-003-019-010

On mains-operated power supplies, the ground wire of the AC line is connected to the power supply chassis. What protection does this provide if a fault occurs in the power supply?

A.
Protects connected equipment from over voltage
B.
Prevents damage to the AC supply circuit breaker
C.
Prevents the equipment fuse from blowing unnecessarily
Correct Answer
D.
Ensures the chassis does not become energized

B-003-019-010

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-003-019-011

Why do fuses have a voltage rating?

A.
To ensure voltage transients can be safely dissipated
B.
To limit current leakage to ground while in operation
Correct Answer
C.
To specify the voltage that can be interrupted without arcing
D.
To prevent dielectric breakdown of the fuse holder

B-003-019-011

If a fuse meant for low voltage is used in a high-voltage circuit, an electric arc may take hold when the fuse opens and allow a flow of current to continue.

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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