General exam: practical circuits
Power supplies, schematics, amplifiers, oscillators, filters and digital signal processing. 33 questions, 10 at a time, starting with ones you haven't seen.
Rules to remember10 key practical circuits rulesShow the rules
- A power supply filter smooths the rectified DC using capacitors and inductors to remove ripple. (p. 59)
- A full-wave center-tap rectifier uses two diodes, each conducting on alternate halves of the cycle from the two ends of a center-tapped transformer. (p. 59)
- A half-wave rectifier passes only one half of each AC cycle, which is 180 degrees. (p. 60)
- A full-wave rectifier uses both halves of the AC cycle, so it converts the full 360 degrees. (p. 60)
- A full-wave rectifier flips each negative half-cycle to positive, so its unfiltered output is DC pulses at twice the AC input frequency. (p. 60)
- A two-input AND gate outputs high only when both inputs are high; any low input gives a low output. (p. 62)
- A Class A amplifier is biased so the device conducts through the entire cycle, 100% of the time. (p. 62)
- A linear amplifier's output is a faithful, larger copy of its input waveform, which is required for modes like SSB. (p. 63)
- I (in-phase) and Q (quadrature) signals are 90 degrees apart, which lets an SDR represent any amplitude and phase. (p. 65)
- In a software-defined radio, filtering, detection and modulation are all done in software rather than with dedicated circuits. (p. 65)
Taken from the explanations to checked practice questions; page numbers link to the official handbook.
Sample practical circuits questions
1.Which of the following components are used in a power supply filter network?
- ACapacitors and inductors
- BDiodes
- CTransformers and transducers
- DAll these choices are correct
Show the answer
✓ A. Capacitors and inductors
A power supply filter smooths the rectified DC using capacitors and inductors to remove ripple.
2.In a Class A amplifier, what percentage of the time does the amplifying device conduct?
- A50%
- B100%
- CLess than 50%
- DMore than 50% but less than 100%
Show the answer
✓ B. 100%
A Class A amplifier is biased so the device conducts through the entire cycle, 100% of the time.
3.Which of the following is characteristic of a direct digital synthesizer (DDS)?
- ARelatively high-power output
- BPure sine wave output
- CVariable output frequency with the stability of a crystal oscillator
- DExtremely narrow tuning range
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✓ C. Variable output frequency with the stability of a crystal oscillator
A DDS builds its output digitally from a crystal-controlled clock, so it can tune across frequencies while keeping crystal stability.
4.Which of the following describes a linear amplifier?
- AAn amplifier in which the output preserves the input waveform
- BAny RF power amplifier used in conjunction with an amateur transceiver
- CA Class C high efficiency amplifier
- DAn amplifier used as a frequency multiplier
Show the answer
✓ A. An amplifier in which the output preserves the input waveform
A linear amplifier's output is a faithful, larger copy of its input waveform, which is required for modes like SSB.