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Canadian Advanced Exam Question Bank

effective 4/01/2007

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A-005-02: RF power amplifiers

A-005-02-01: The output tuning controls on a transmitter power amplifier:

allow efficient transfer of power to the antenna

allow switching to different antennas

reduce the possibility of cross-modulation in adjunct receivers

are involved with frequency multiplication in the previous stage



A-005-02-02: The purpose of using a centre-tap return connection on the secondary of transmitting tube's filament transformer is to:

prevent modulation of the emitted wave by the alternating current filament supply

reduce the possibility of harmonic emissions

keep the output voltage constant with a varying load

obtain optimum power output



A-005-02-03: In a grounded grid amplifier using a triode vacuum tube, the input signal is applied to:

the cathode

the plate

the control grid

the filaments



A-005-02-04: In a grounded grid amplifier using a triode vacuum tube, the plate is connected to the pi-network through a:

blocking capacitor

by-pass capacitor

tuning capacitor

electrolytic capacitor



A-005-02-05: In a grounded grid amplifier using a triode vacuum tube, the plate is connected to a radio frequency choke. The other end of the radio frequency choke connects to the:

B+ (high voltage)

filament voltage

ground

B- (bias)



A-005-02-06: In a grounded grid amplifier using a triode vacuum tube, the cathode is connected to a radio frequency choke. The other end of the radio frequency choke connects to the:

B- (bias)

ground

filament voltage

B+ (high voltage)



A-005-02-07: In a grounded grid amplifier using a triode vacuum tube, the secondary winding of a transformer is connected directly to the vacuum tube. This transformer provides:

filament voltage

B- (bias)

B+ (high voltage)

Screen voltage



A-005-02-08: In a grounded grid amplifier using a triode vacuum tube, what would be the approximate B+ voltage required for an output of 400 watts at 400 mA with approximately 50 percent efficiency?

2000 volts

500 volts

3000 volts

1000 volts



A-005-02-09: In a grounded grid amplifier using a triode vacuum tube, each side of the filament is connected to a capacitor whose other end is connected to ground. These are:

by-pass capacitors

tuning capacitors

electrolytic capacitors

blocking capacitors



A-005-02-10: After you have opened a VHF power amplifier to make internal tuning adjustments, what should you do before you turn the amplifier on?

Be certain all amplifier shielding is fastened in place

Make sure that the power interlock switch is bypassed so you can test the amplifier

Be certain no antenna is attached so that you will not cause any interference

Remove all amplifier shielding to ensure maximum cooling



A-005-02-11: Harmonics produced in an early stage of a transmitter may be reduced in a later stage by:

tuned circuit coupling between stages

larger value coupling capacitors

greater input to the final stage

transistors instead of tubes





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A-005-01: Oscillator circuits, phase locked loop (PLL)
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A-005-03: Transmitters, neutralisation
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