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

A conventional FM phone signal occupies approximately 16 kHz of bandwidth due to the deviation and modulation index used.

Question 2

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

Accepted Answer

WINMOR

Answer

WINMOR uses OFDM techniques to provide robust digital communication over HF amateur radio channels.

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

A balanced modulator combines the carrier and audio signals in a way that cancels the carrier, outputting only the two sidebands.

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

Increasing the modulating frequency while keeping deviation constant increases the occupied bandwidth per Carson's rule.

Question 5

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

Accepted Answer

A 180-degree phase shift

Answer

In BPSK31, a binary zero is represented by a 180-degree phase reversal of the carrier signal.

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