HAM Practical Circuits and Components 2

Question 1

What is the primary advantage of using a toroidal core inductor over an air-core inductor in an RF circuit?

Accepted Answer

Magnetic flux is contained within the core, reducing radiation

Answer

Toroidal cores confine the magnetic field within the ferrite or powdered-iron material, minimizing stray coupling and EMI radiation.

Question 2

A MOSFET used as an RF amplifier exhibits a gate-to-drain capacitance (Cgd). What circuit effect does this primarily cause?

Accepted Answer

Miller effect multiplying the effective input capacitance

Answer

The Miller effect multiplies Cgd by (1 + voltage gain), dramatically increasing the apparent input capacitance and affecting amplifier bandwidth.

Question 3

Which type of diode is specifically designed to operate in the reverse-breakdown region for voltage regulation?

Accepted Answer

Zener diode

Answer

Zener diodes are doped to have a precise, stable reverse breakdown voltage used for voltage regulation.

Question 4

In a crystal-controlled oscillator, what determines the fundamental resonant frequency of the quartz crystal?

Accepted Answer

The physical dimensions and cut angle of the crystal

Answer

The resonant frequency of a quartz crystal is determined by its physical thickness and the crystallographic cut angle used during manufacturing.

Question 5

What is the function of a bypass capacitor placed at the power supply pin of an RF amplifier IC?

Accepted Answer

To provide a low-impedance path for RF currents to prevent feedback through the supply rail

Answer

Bypass capacitors shunt RF currents to ground at the supply pin, preventing them from coupling back through the power supply and causing instability.

HAM - Radio Extra Class Test Practice Test