HAM FREE HAM Radio Extra Class Test Practical Circuits and Components Questions and Answers 2 — Questions and Answers
Question 1: What is the primary advantage of a Chebyshev low-pass filter design compared to a Butterworth design of the same order?
- Steeper rolloff in the stopband (Correct answer)
- Flatter passband response
- Lower component count
- Higher power handling
Correct answer: Steeper rolloff in the stopband
Chebyshev filters achieve a steeper transition from passband to stopband than Butterworth filters of the same order, at the cost of passband ripple.
Question 2: In a Class AB push-pull amplifier, what is the purpose of the slight forward bias applied to both transistors?
- To reduce crossover distortion (Correct answer)
- To increase power output
- To improve frequency response
- To lower the input impedance
Correct answer: To reduce crossover distortion
The slight forward bias in Class AB operation keeps both transistors conducting near the zero-crossing point, eliminating the crossover distortion seen in pure Class B designs.
Question 3: What type of circuit is typically used to generate a stable reference frequency from a crystal oscillator for a PLL synthesizer?
- Temperature-compensated crystal oscillator (TCXO) (Correct answer)
- Hartley oscillator
- Phase-shift oscillator
- Wien bridge oscillator
Correct answer: Temperature-compensated crystal oscillator (TCXO)
A TCXO provides the highly stable reference frequency needed by PLL synthesizers to maintain accurate output frequencies across temperature variations.
Question 4: What is the function of a diplexer in an amateur radio station?
- To allow simultaneous operation on two different bands using one antenna (Correct answer)
- To split an audio signal into two channels
- To combine two power amplifiers into one output
- To match impedance between a transceiver and a dummy load
Correct answer: To allow simultaneous operation on two different bands using one antenna
A diplexer uses frequency-selective filters to route signals of different frequency bands to or from a single antenna without mutual interference.
Question 5: Which component in a superheterodyne receiver is responsible for rejecting the image frequency?
- The preselector or front-end bandpass filter (Correct answer)
- The IF amplifier
- The AGC circuit
- The beat frequency oscillator
Correct answer: The preselector or front-end bandpass filter
The preselector filter ahead of the mixer attenuates the image frequency, which is separated from the desired signal by twice the IF.
Question 6: What is the primary purpose of neutralization in a vacuum tube or transistor RF amplifier?
- To cancel internal feedback that causes self-oscillation (Correct answer)
- To balance the push-pull output stages
- To equalize gain across the operating bandwidth
- To reduce harmonic distortion in the output
Correct answer: To cancel internal feedback that causes self-oscillation
Neutralization introduces a signal equal in amplitude but opposite in phase to the internal feedback path, preventing the amplifier from breaking into unwanted oscillation.
HAM FREE HAM Radio Extra Class Test Practical Circuits and Components Questions and Answers 2
What is the primary advantage of a Chebyshev low-pass filter design compared to a Butterworth design of the same order?