HAM Practical Electronics Circuits 4

Question 1

What is the purpose of a PIN diode in an RF switching circuit?

Accepted Answer

To act as a variable resistance controlled by DC bias current

Answer

A PIN diode's intrinsic region resistance is controlled by DC bias, allowing it to act as a voltage-controlled switch or attenuator at RF frequencies.

Question 2

In a phase-locked loop (PLL), what does the voltage-controlled oscillator (VCO) receive as its control input?

Accepted Answer

The filtered error voltage from the phase detector

Answer

The low-pass filter smooths the phase detector output into a DC error voltage that steers the VCO frequency until it locks to the reference.

Question 3

Which of the following best describes the function of a diplexer at an antenna connection?

Accepted Answer

It separates two frequency bands so they can share one antenna

Answer

A diplexer uses filters to route two different frequency bands to and from a shared antenna while isolating each port from the other.

Question 4

What is the main advantage of a push-pull amplifier configuration over a single-ended amplifier?

Accepted Answer

Cancellation of even-order harmonic distortion

Answer

In push-pull circuits, the two transistors handle opposite half-cycles and their even-order distortion products cancel in the output transformer.

Question 5

What happens to the Q factor of an LC resonant circuit when resistance is added in series with the inductor?

Accepted Answer

Q decreases because losses increase

Answer

Q = ωL/R, so increasing series resistance reduces Q, which broadens the resonance bandwidth and reduces selectivity.

HAM - Radio Extra Class Test Practice Test

HAM - Radio Extra Class Test Practice Test

HAM Practical Electronics Circuits 4