HAM Radio Extra Class Test Practical Electronics Circuits Questions and Answers

Question 1

What is the key difference in the feedback mechanism between a Colpitts oscillator and a Hartley oscillator?

Accepted Answer

A Colpitts uses a tapped capacitive divider, while a Hartley uses a tapped inductor.

Answer

A Colpitts uses a tapped inductor, while a Hartley uses a tapped capacitive divider.

Answer

A Colpitts uses piezoelectric crystal feedback, while a Hartley uses a tank circuit.

Answer

A Colpitts requires positive feedback, while a Hartley requires negative feedback.

Question 2

In a radio receiver front-end, a JFET is often preferred over a MOSFET for the initial RF amplifier stage. What is the primary reason for this design choice?

Accepted Answer

JFETs typically have a significantly lower noise figure.

Answer

JFETs have a much higher power handling capability.

Answer

JFETs are less susceptible to damage from electrostatic discharge (ESD).

Answer

JFETs operate in enhancement mode, simplifying biasing.

Question 3

Which of the following circuits is specifically designed to convert a noisy or slowly changing analog signal into a clean digital signal with distinct high and low levels by using hysteresis?

Accepted Answer

A Schmitt trigger

Answer

A passive LC low-pass filter

Answer

A differential amplifier

Answer

An astable multivibrator

Question 4

A technician is building an audio filter for a CW (Morse code) receiver to create a very narrow passband around 700 Hz. Which of the following would be the most significant advantage of using an active filter with operational amplifiers (op-amps) over a passive LC filter for this application?

Accepted Answer

Active filters can provide signal gain and are easily cascaded for higher Q.

Answer

Active filters do not require a power source.

Answer

Passive filters are much smaller and lighter for audio frequencies.

Answer

Active filters have superior performance at microwave frequencies.

Question 5

What is the primary function of a double-balanced mixer in a superheterodyne receiver?

Accepted Answer

To combine the RF and local oscillator signals, producing sum and difference frequencies while suppressing the original input signals.

Answer

To amplify the incoming RF signal while rejecting the image frequency.

Answer

To provide a stable reference frequency for the local oscillator.

Answer

To filter the intermediate frequency (IF) signal, providing narrow selectivity.

Question 6

In an operational amplifier configured as a non-inverting amplifier, what primarily determines the circuit's voltage gain?

Accepted Answer

The values of the input resistor and the feedback resistor.

Answer

The op-amp's open-loop gain and the input signal frequency.

Answer

The power supply voltage.

Answer

The input offset voltage of the op-amp.