A-005-03: Transmitters, neutralisation
A-005-03-01:
In a simple 2 stage CW transmitter circuit, the oscillator stage and the class C amplifier stage are inductively coupled by a RF transformer. Another role of the RF transformer is to:
be part of a tuned circuit
act as part of a pi filter
provide the necessary feedback for oscillation
act as part of a balanced mixer
A-005-03-02:
In a simple 2 stage CW transmitter, current to the collector of the transistor in the class C amplifier stage flows through a radio frequency choke (RFC) and a tapped inductor. The RFC, on the tapped inductor side, is also connected to grounded capacitors. The purpose of the RFC and capacitors is to:
form a low-pass filter
provide negative feedback
form a key-click filter
form a RF-tuned circuit
A-005-03-03:
In a simple 2 stage CW transmitter, the transistor in the second stage would act as:
a power amplifier
a frequency multiplier
the master oscillator
an audio oscillator
A-005-03-04:
An advantage of keying the buffer stage in a transmitter is that:
changes in oscillator frequency are less likely
key clicks are eliminated
the radiated bandwidth is restricted
high RF voltages are not present
A-005-03-05:
As a power amplifier is tuned, what reading on its grid-current meter indicates the best neutralization?
A minimum change in grid current as the output circuit is changed
Minimum grid current
Maximum grid current
A maximum change in grid current as the output circuit is changed
A-005-03-06:
What does a neutralizing circuit do in an RF amplifier?
It cancels the effects of positive feedback
It eliminates AC hum from the power supply
It reduces incidental grid modulation
It controls differential gain
A-005-03-07:
What is the reason for neutralizing the final amplifier stage of a transmitter?
To eliminate self-oscillations
To limit the modulation index
To cut off the final amplifier during standby periods
To keep the carrier on frequency
A-005-03-08:
Parasitic oscillations are usually generated due to:
accidental resonant frequencies in the power amplifier
harmonics from some earlier multiplier stage
excessive drive or excitation to the power amplifier
a mismatch between power amplifier and feedline
A-005-03-09:
Parasitic oscillations would tend to occur mostly in:
RF power output stages
high gain audio output stages
high voltage rectifiers
mixer stages
A-005-03-10:
Why is neutralization necessary for some vacuum-tube amplifiers?
To cancel oscillation caused by the effects of interelectrode capacitance
To reduce grid-to-cathode leakage
To cancel AC hum from the filament transformer
To reduce the limits of loaded Q
A-005-03-11:
Parasitic oscillations in an RF power amplifier may be caused by:
lack of neutralisation
overdriven stages
unintended tuned circuits
excessive harmonic production
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