HAM HAM Radio Extra Class Test Modulation and Digital Signals Questions and Answers 2

Question 1

What is the approximate bandwidth of a conventional FM phone signal on the HF bands?

Accepted Answer

About 16 kHz

Answer

About 6 kHz

Answer

About 30 kHz

Answer

About 3 kHz

Question 2

Which digital mode uses orthogonal frequency-division multiplexing (OFDM) for amateur HF communication?

Accepted Answer

WINMOR

Answer

PSK31

Answer

RTTY

Answer

CW

Question 3

What is the function of a balanced modulator in a single sideband transmitter?

Accepted Answer

It suppresses the carrier while producing upper and lower sidebands

Answer

It amplifies only the desired sideband

Answer

It filters out audio frequencies above 3 kHz

Answer

It generates the intermediate frequency

Question 4

What happens to the bandwidth of an FM signal if the deviation is held constant and the modulating frequency is doubled?

Accepted Answer

The bandwidth increases

Answer

The bandwidth decreases

Answer

The bandwidth stays the same

Answer

The bandwidth is cut in half

Question 5

In a PSK31 signal, what type of modulation shift represents a binary zero?

Accepted Answer

A 180-degree phase shift

Answer

No phase shift

Answer

A 90-degree phase shift

Answer

A frequency shift of 31 Hz

Question 6

What is the purpose of interleaving in digital communication modes used on amateur radio?

Accepted Answer

To spread burst errors across multiple code blocks so error correction can recover the data

Answer

To increase the data transmission rate

Answer

To reduce the power required for transmission

Answer

To compress the signal bandwidth