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Subelement 2

Advanced Components and Circuits

Section 2-09

mixers, frequency multipliers

What is the mixing process?

  • The elimination of noise in a wideband receiver by phase differentiation
  • The recovery of intelligence from a modulated signal
  • Correct Answer
    The combination of two signals to produce sum and difference frequencies
  • The elimination of noise in a wideband receiver by phase comparison
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What are the principal frequencies that appear at the output of a mixer circuit?

  • Correct Answer
    The original frequencies and the sum and difference frequencies
  • 1.414 and 0.707 times the input frequencies
  • The sum, difference and square root of the input frequencies
  • Two and four times the original frequency
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What occurs when an excessive amount of signal energy reaches the mixer circuit?

  • Automatic limiting occurs
  • Correct Answer
    Spurious signals are generated
  • A beat frequency is generated
  • Mixer blanking occurs
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In a frequency multiplier circuit, the input signal is coupled to the base of a transistor through a capacitor. A radio frequency choke is connected between the base of the transistor and ground. The capacitor is:

  • Correct Answer
    a DC blocking capacitor
  • part of the input tuned circuit
  • a by-pass for the circuit
  • part of the output tank circuit
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A frequency multiplier circuit must be operated in:

  • class AB
  • class B
  • class A
  • Correct Answer
    class C
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In a frequency multiplier circuit, an inductance (L1) and a variable capacitor (C2) are connected in series between VCC+ and ground. The collector of a transistor is connected to a tap on L1. The purpose of the variable capacitor is to:

  • Correct Answer
    tune L1 to the desired harmonic
  • by-pass RF
  • tune L1 to the frequency applied to the base
  • provide positive feedback
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In a frequency multiplier circuit, an inductance (L1) and a variable capacitor (C2) are connected in series between VCC+ and ground. The collector of a transistor is connected to a tap on L1. A fixed capacitor (C3) is connected between the VCC+ side of L1 and ground. The purpose of C3 is to:

  • form a pi filter with L1 and C2
  • resonate with L1
  • Correct Answer
    keep RF out of the power supply
  • by-pass any audio components
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In a frequency multiplier circuit, an inductance (L1) and a variable capacitor (C2) are connected in series between VCC+ and ground. The collector of a transistor is connected to a tap on L1. C2 in conjunction with L1 operate as a:

  • frequency divider
  • Correct Answer
    frequency multiplier
  • voltage divider
  • voltage doubler
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In a circuit where the components are tuned to resonate at a higher frequency than applied, the circuit is most likely a:

  • Correct Answer
    a frequency multiplier
  • a VHF/UHF amplifier
  • a linear amplifier
  • a frequency divider
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In a frequency multiplier circuit, an inductance (L1) and a variable capacitor (C2) are connected in series between VCC+ and ground. The collector of a transistor is connected to a tap on L1. A fixed capacitor (C3) is connected between the VCC+ side of L1 and ground. C3 is a:

  • DC blocking capacitor
  • tuning capacitor
  • Correct Answer
    RF by-pass capacitor
  • coupling capacitor
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What stage in a transmitter would change a 5.3-MHz input signal to 14.3 MHz?

  • A linear translator
  • A frequency multiplier
  • Correct Answer
    A mixer
  • A beat frequency oscillator
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