GROL Receivers and Transmitters 3

Question 1

What is the function of a buffer amplifier stage in a transmitter?

Accepted Answer

To isolate the master oscillator from load variations that could cause frequency pulling

Answer

A buffer amplifier presents a stable, high-impedance load to the oscillator so that changes in subsequent stages do not pull the oscillator off frequency.

Question 2

At 100% amplitude modulation, what percentage of total transmitted power is contained in the carrier?

Accepted Answer

66.7%

Answer

At 100% modulation, each sideband carries 25% of the carrier power, so total power = 1.5 × Pc; the carrier fraction is 1/1.5 ≈ 66.7%.

Question 3

A frequency multiplier stage in an FM transmitter:

Accepted Answer

Multiplies both the carrier frequency and the frequency deviation by the same integer factor

Answer

Frequency multipliers multiply every frequency component, so both the center frequency and the peak deviation increase by the same factor.

Question 4

What is the primary purpose of the low-pass filter at the output of a transmitter?

Accepted Answer

To suppress harmonic and spurious emissions before the signal reaches the antenna

Answer

The low-pass filter passes the fundamental transmit frequency but attenuates harmonics and other spurious products that could interfere with other services.

Question 5

A final RF amplifier has a DC input of 100 W and an RF output of 60 W. What is its efficiency?

Accepted Answer

60%

Answer

Efficiency = (RF output / DC input) × 100% = (60 W / 100 W) × 100% = 60%.

(GROL) General Radiotelephone Operator License Practice Test

(GROL) General Radiotelephone Operator License Practice Test

GROL Receivers and Transmitters 3