HAM Practical Electronics Circuits 5

Question 1

What is the primary function of a low-noise amplifier (LNA) placed at the front end of a receiver?

Accepted Answer

To establish the noise figure of the entire receive chain

Answer

The first amplifier in a cascade dominates overall noise figure per Friis's formula, so an LNA with low noise figure minimizes the receiver's noise floor.

Question 2

In a Colpitts oscillator, the feedback network consists of:

Accepted Answer

Two capacitors forming a voltage divider with an inductor

Answer

The Colpitts oscillator uses a capacitive voltage divider (two capacitors in series) with an inductor to set frequency and provide feedback.

Question 3

What does a spectrum analyzer display that a conventional oscilloscope cannot directly show?

Accepted Answer

Signal amplitude as a function of frequency

Answer

A spectrum analyzer plots amplitude versus frequency, revealing harmonics, spurious outputs, and modulation sidebands that are hidden in a time-domain oscilloscope view.

Question 4

Which type of logic family typically has the lowest power consumption at low switching frequencies?

Accepted Answer

CMOS (complementary MOS)

Answer

CMOS draws negligible static current because one transistor in each complementary pair is always off, making it far more power-efficient than bipolar logic families at low frequencies.

Question 5

What is the purpose of a tank circuit in an RF power amplifier output stage?

Accepted Answer

To reconstruct the full RF waveform and filter harmonics

Answer

The tank circuit stores energy and resonates at the carrier frequency, restoring the sinusoidal waveform from the amplifier's current pulses and suppressing harmonics.

HAM - Radio Extra Class Test Practice Test

HAM - Radio Extra Class Test Practice Test

HAM Practical Electronics Circuits 5