HAM Practical Circuits and Components 5

Question 1

In a Colpitts oscillator, what elements form the feedback voltage divider?

Accepted Answer

Two capacitors in series across the tank inductor

Answer

The Colpitts oscillator uses a capacitive voltage divider (two capacitors in series) tapped across the tank inductor to feed back the correct phase and amplitude.

Question 2

What is the significance of the '1 dB compression point' specification for an RF amplifier?

Accepted Answer

The output power level where gain has dropped 1 dB below the linear gain value due to saturation

Answer

The 1 dB compression point marks the onset of significant non-linearity — above this level, gain compresses and distortion products increase rapidly.

Question 3

Why is a low-pass filter connected between a transmitter and its antenna?

Accepted Answer

To attenuate harmonic and spurious emissions that could interfere with other services

Answer

Low-pass filters suppress harmonics and other spurious signals above the transmit frequency, keeping the transmitted spectrum within FCC limits.

Question 4

What happens to the resonant frequency of an LC tank circuit if the inductor core is partially removed?

Accepted Answer

Resonant frequency increases because inductance decreases

Answer

Removing core material reduces the effective permeability, lowering inductance; since f = 1/(2π√LC), lower L raises the resonant frequency.

Question 5

A cascode amplifier consists of what transistor configuration?

Accepted Answer

A common-emitter stage driving a common-base stage

Answer

The cascode pairs a common-emitter (or common-source) input with a common-base (common-gate) output, reducing the Miller effect and extending bandwidth while maintaining gain.

HAM - Radio Extra Class Test Practice Test

HAM - Radio Extra Class Test Practice Test

HAM Practical Circuits and Components 5