E7H01

What are three major oscillator circuits often used in Amateur Radio equipment?

1. Colpitts, Hartley and Pierce

E7H02

What condition must exist for a circuit to oscillate?

1. It must have a positive feedback loop with a gain greater than 1

E7H03

How is positive feedback supplied in a Hartley oscillator?

1. Through a tapped coil

E7H04

How is positive feedback supplied in a Colpitts oscillator?

1. Through a capacitive divider

E7H05

How is positive feedback supplied in a Pierce oscillator?

1. Through a quartz crystal

E7H06

Which type of oscillator circuits are commonly used in VFOs?

1. Colpitts and Hartley

E7H07

What is a magnetron oscillator?

1. A UHF or microwave oscillator consisting of a diode vacuum tube with a specially shaped anode, surrounded by an external magnet

E7H08

What is a Gunn diode oscillator?

1. An oscillator based on the negative resistance properties of properly-doped semiconductors

E7H09

What type of frequency synthesizer circuit uses a stable voltage-controlled oscillator, programmable divider, phase detector, loop filter and a reference frequency source?

1. A phase locked loop 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?

1. A direct digital synthesizer

E7H11

What information is contained in the lookup table of a direct digital frequency synthesizer?

1. The amplitude values that represent a sine-wave output

E7H12

What are the major spectral impurity components of direct digital synthesizers?

1. Spurs at discrete frequencies

E7H13

Which of these circuits would be classified as a principal component of a direct digital synthesizer (DDS)?

1. Phase accumulator

E7H14

What circuit is often used in conjunction with a direct digital synthesizer (DDS) to expand the available tuning range?

1. Phase locked loop

E7H15

What is the capture range of a phase-locked loop circuit?

1. The frequency range over which the circuit can lock

E7H16

What is a phase-locked loop circuit?

1. An electronic servo loop consisting of a phase detector, a low-pass filter and voltage-controlled oscillator

E7H17

Which of these functions can be performed by a phase-locked loop?

1. Frequency synthesis, FM demodulation

E7H18

Why is a stable reference oscillator normally used as part of a phase locked loop (PLL) frequency synthesizer?

1. Any phase variations in the reference oscillator signal will produce phase noise in the synthesizer output

E7H19

Why is a phase-locked loop often used as part of a variable frequency synthesizer for receivers and transmitters?

1. It makes it possible for a VFO to have the same degree of stability as a crystal oscillator

E7H20

What are the major spectral impurity components of phase-locked loop synthesizers?

1. Broadband noise

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