Practical Circuits and Components Flashcards
7 cards from real HAM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Practical Circuits and Components flashcards as text
In a superheterodyne receiver, what is the purpose of the IF (intermediate frequency) filter?
Answer: To provide selectivity by passing only a narrow band of frequencies centered on the IF
The IF filter provides the receiver's primary selectivity, rejecting adjacent channels while passing the desired signal at the fixed intermediate frequency.
What type of transistor configuration provides voltage gain greater than unity, current gain approximately equal to unity, and low output impedance?
Answer: Common collector (emitter follower)
The common-collector (emitter follower) configuration has near-unity current gain, voltage gain slightly less than one, high input impedance, and low output impedance.
Which component characteristic is most important when selecting a capacitor for use in a high-Q resonant circuit?
Answer: Low ESR and low dielectric loss (high Q)
Low ESR and low dielectric loss ensure minimal energy dissipation, maintaining the high Q of the resonant circuit.
A PIN diode is used as an RF switch. What controls its RF resistance?
Answer: The DC bias current through it
The RF resistance of a PIN diode is controlled by the DC bias current — higher forward current reduces resistance, making it conductive at RF.
What is the function of an automatic level control (ALC) circuit in an SSB transmitter?
Answer: To limit the RF output power to prevent overdrive and distortion
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.
What is the primary disadvantage of using a switching (switch-mode) power supply in a ham radio station compared to a linear supply?
Answer: Generation of broadband RF interference across many frequencies
Switching power supplies generate harmonic noise across a wide frequency range due to their high-frequency switching action, potentially causing interference in receivers.
In a phase-locked loop (PLL) synthesizer, what component compares the VCO output frequency to the reference and generates an error signal?
Answer: The phase-frequency detector
The phase-frequency detector (PFD) compares the phase and frequency of the divided VCO output to the reference oscillator and produces a correction voltage.