E7H: Oscillators and signal sources: types of oscillators; synthesizers and phase-locked loops; direct digital synthesizers
E7H01:
What are three major oscillator circuits often used in Amateur Radio equipment?
Colpitts, Hartley and Pierce
Taft, Pierce and negative feedback
Pierce, Fenner and Beane
Taft, Hartley and Pierce
E7H02:
What condition must exist for a circuit to oscillate?
It must have a positive feedback loop with a gain greater than 1
It must have at least two stages
It must be neutralized
It must have negative feedback sufficient to cancel the input signal
E7H03:
How is positive feedback supplied in a Hartley oscillator?
Through a tapped coil
Through a capacitive divider
Through link coupling
Through a neutralizing capacitor
E7H04:
How is positive feedback supplied in a Colpitts oscillator?
Through a capacitive divider
Through a tapped coil
Through link coupling
Through a neutralizing capacitor
E7H05:
How is positive feedback supplied in a Pierce oscillator?
Through a quartz crystal
Through a tapped coil
Through link coupling
Through a neutralizing capacitor
E7H06:
Which type of oscillator circuits are commonly used in VFOs?
Colpitts and Hartley
Pierce and Zener
Armstrong and deForest
Negative feedback and Balanced feedback
E7H07:
What is a magnetron oscillator?
A UHF or microwave oscillator consisting of a diode vacuum tube with a specially shaped anode, surrounded by an external magnet
An oscillator in which the output is fed back to the input by the magnetic field of a transformer
An crystal oscillator in which variable frequency is obtained by placing the crystal in a strong magnetic field
A reference standard oscillator in which the oscillations are synchronized by magnetic coupling to a rubidium gas tube
E7H08:
What is a Gunn diode oscillator?
An oscillator based on the negative resistance properties of properly-doped semiconductors
An oscillator based on the argon gas diode
A highly stable reference oscillator based on the tee-notch principle
A highly stable reference oscillator based on the hot-carrier effect
E7H09:
What type of frequency synthesizer circuit uses a stable voltage-controlled oscillator, programmable divider, phase detector, loop filter and a reference frequency source?
A phase locked loop synthesizer
A direct digital synthesizer
A hybrid synthesizer
A diode-switching matrix synthesizer
E7H10:
What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital to analog converter and a low-pass anti-alias filter?
A direct digital synthesizer
A hybrid synthesizer
A phase locked loop synthesizer
A diode-switching matrix synthesizer
E7H11:
What information is contained in the lookup table of a direct digital frequency synthesizer?
The amplitude values that represent a sine-wave output
The phase relationship between a reference oscillator and the output waveform
The phase relationship between a voltage-controlled oscillator and the output waveform
The synthesizer frequency limits and frequency values stored in the radio memories
E7H12:
What are the major spectral impurity components of direct digital synthesizers?
Spurs at discrete frequencies
Broadband noise
Digital conversion noise
Nyquist limit noise
E7H13:
Which of these circuits would be classified as a principal component of a direct digital synthesizer (DDS)?
Phase accumulator
Phase splitter
Hex inverter
Chroma demodulator
E7H14:
What circuit is often used in conjunction with a direct digital synthesizer (DDS) to expand the available tuning range?
Phase locked loop
Binary expander
J-K flip-flop
Compander
E7H15:
What is the capture range of a phase-locked loop circuit?
The frequency range over which the circuit can lock
The voltage range over which the circuit can lock
The input impedance range over which the circuit can lock
The range of time it takes the circuit to lock
E7H16:
What is a phase-locked loop circuit?
An electronic servo loop consisting of a phase detector, a low-pass filter and voltage-controlled oscillator
An electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator
An electronic circuit also known as a monostable multivibrator
An electronic circuit consisting of a precision push-pull amplifier with a differential input
E7H17:
Which of these functions can be performed by a phase-locked loop?
Frequency synthesis, FM demodulation
Wide-band AF and RF power amplification
Comparison of two digital input signals, digital pulse counter
Photovoltaic conversion, optical coupling
E7H18:
Why is a stable reference oscillator normally used as part of a phase locked loop (PLL) frequency synthesizer?
Any phase variations in the reference oscillator signal will produce phase noise in the synthesizer output
Any amplitude variations in the reference oscillator signal will prevent the loop from locking to the desired signal
Any phase variations in the reference oscillator signal will produce harmonic distortion in the modulating signal
Any amplitude variations in the reference oscillator signal will prevent the loop from changing frequency
E7H19:
Why is a phase-locked loop often used as part of a variable frequency synthesizer for receivers and transmitters?
It makes it possible for a VFO to have the same degree of stability as a crystal oscillator
It generates FM sidebands
It eliminates the need for a voltage controlled oscillator
It can be used to generate or demodulate SSB signals by quadrature phase synchronization
E7H20:
What are the major spectral impurity components of phase-locked loop synthesizers?
Broadband noise
Digital conversion noise
Spurs at discrete frequencies
Nyquist limit noise
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