HAM Practical Circuits and Components 3

Question 1

In a superheterodyne receiver, what is the purpose of the IF (intermediate frequency) filter?

Accepted Answer

To provide selectivity by passing only a narrow band of frequencies centered on the IF

Answer

The IF filter provides the receiver's primary selectivity, rejecting adjacent channels while passing the desired signal at the fixed intermediate frequency.

Question 2

What type of transistor configuration provides voltage gain greater than unity, current gain approximately equal to unity, and low output impedance?

Accepted Answer

Common collector (emitter follower)

Answer

The common-collector (emitter follower) configuration has near-unity current gain, voltage gain slightly less than one, high input impedance, and low output impedance.

Question 3

Which component characteristic is most important when selecting a capacitor for use in a high-Q resonant circuit?

Accepted Answer

Low ESR and low dielectric loss (high Q)

Answer

Low ESR and low dielectric loss ensure minimal energy dissipation, maintaining the high Q of the resonant circuit.

Question 4

A PIN diode is used as an RF switch. What controls its RF resistance?

Accepted Answer

The DC bias current through it

Answer

The RF resistance of a PIN diode is controlled by the DC bias current — higher forward current reduces resistance, making it conductive at RF.

Question 5

What is the function of an automatic level control (ALC) circuit in an SSB transmitter?

Accepted Answer

To limit the RF output power to prevent overdrive and distortion

Answer

The ALC circuit senses the RF output level and reduces the drive to the final amplifier to prevent flat-topping and intermodulation distortion on peaks.

HAM - Radio Extra Class Test Practice Test

HAM - Radio Extra Class Test Practice Test

HAM Practical Circuits and Components 3