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26 Cards in this Set
- Front
- Back
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What are the four basic transmitter types?
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Am, fm, cw, ssb
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What is the function of the oscillator in a cw transmitter?
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It generates an rf carrier at a given frequency within required limits
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What is the final stage of a transmitter?
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Power amplifier
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What purpose does a microphone perform in an AM transmitter?
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It converts audio (sound) into electrical energy
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In an fm transmitter, when does an oscillator generate only a steady frequency?
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When no modulation is present.
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What is a harmonic?
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It is an exact multiple of the basic or fundamental frequency
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If the fundamental frequency is 200 megahertz, what is the third harmonic?
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600 megahertz.
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Why are frequency multipliers used?
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To obtain higher carrier frequencies
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What are two advantages of ssb transmission?
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It saves power and frequency bandwidth.
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What is the purpose of an order-wire circuit?
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For operator-to-operator service messages and frequency changes
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What four basic functions must a receiver perform?
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Reception, selection, detection, and reproduction.
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What are the four basic receiver characteristics?
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Sensitivity, noise, selectivity, and fidelity
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What frequency conversion principle is used to develop the IF?
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Heterodyning.
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What is the function of the detector?
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To extract the modulating audio signal.
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What is the major disadvantage of an fm signal as compared to an AM signal?
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Wide bandpass.
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What two components give a ssb receiver its advantages over an AM superheterodyne receiver?
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A special type of detector and a carrier reinsertion oscillator.
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What does manual gain control do to strong and weak signals, respectively?
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Attenuates the strong and amplifies the weak.
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What is the purpose of agc/avc in a receiver?
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To limit unwanted variations in the output.
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What is a disadvantage of agc?
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Weak signals produce bias, which could result in no usable receiver output.
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What is the main difference between agc and dagc?
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Dagc does not attenuate weak signals
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What is the function of the bfo?
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It is heterodyned with the rf to produce an audio frequency.
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What is the purpose of a squelch circuit?
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It eliminates noise when no signal is being received.
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What does a tone control circuit in a receiver do to the audio signal?
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It controls the amount of bass and treble response.
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What is the function of a crystal filter in a receiver?
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It is used to achieve maximum selectivity.
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What is the primary function of an afc circuit?
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It is used to accurately control the frequency of the oscillator.
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What is frequency synthesis?
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The process of selecting and/or heterodyning frequencies to produce a signal frequency.
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