Extra Class Exam Question Pool

effective 7/01/2008 thru 6/30/2012

 Show: Unseen questions Weak questions Review questions Learned questions Incorrect answer choices

E7F: Frequency markers and counters: frequency divider circuits; frequency marker generators; frequency counters

E7F01: What is the purpose of a prescaler circuit?

It divides a higher frequency signal so a low-frequency counter can display the operating frequency

It converts the output of a JK flip-flop to that of an RS flip-flop

It multiplies a higher frequency signal so a low-frequency counter can display the operating frequency

It prevents oscillation in a low-frequency counter circuit

E7F02: Which of the following would be used to reduce a signal’s frequency by a factor of ten?

A prescaler

A preamp

A marker generator

A flip-flop

E7F03: What is the function of a decade counter digital IC?

It produces one output pulse for every ten input pulses

It decodes a decimal number for display on a seven-segment LED display

It produces ten output pulses for every input pulse

It adds two decimal numbers together

E7F04: What additional circuitry must be added to a 100-kHz crystal-controlled marker generator so as to provide markers at 50 and 25 kHz?

Two flip-flops

An emitter-follower

Two frequency multipliers

A voltage divider

E7F05: Which of the following circuits can be combined to produce a 100 kHz fundamental signal with harmonics at 100 kHz intervals?

A 1 MHz oscillator and a decade counter

A 10 MHz oscillator and a flip-flop

A 1 MHz oscillator and a flip-flop

A 100 kHz oscillator and a phase detector

E7F06: Which of these choices best describes a crystal marker generator?

A crystal-controlled oscillator that generates a series of reference signals at known frequency intervals

A low-stability oscillator that sweeps through a band of frequencies

An oscillator often used in aircraft to determine the craft's location relative to the inner and outer markers at airports

A crystal-controlled oscillator with an output frequency and amplitude that can be varied over a wide range

E7F07: Which type of circuit would be a good choice for generating a series of harmonically related receiver calibration signals?

A crystal oscillator followed by a frequency divider

A Wein-bridge oscillator followed by a class-A amplifier

A Foster-Seeley discriminator

A phase-shift oscillator

E7F08: What is one purpose of a marker generator?

To provide a means of calibrating a receiver's frequency settings

To add audio markers to an oscilloscope

To provide a frequency reference for a phase locked loop

To add time signals to a transmitted signal

E7F09: What determines the accuracy of a frequency counter?

The accuracy of the time base

The speed of the logic devices used

Accuracy of the AC input frequency to the power supply

Proper balancing of the mixer diodes

E7F10: How does a conventional frequency counter determine the frequency of a signal?

It counts the number of input pulses occurring within a specific period of time

It counts the total number of pulses in a circuit

It monitors a WWV reference signal for comparison with the measured signal

It converts the phase of the measured signal to a voltage which is proportional to the frequency

E7F11: What is the purpose of a frequency counter?

To provide a digital representation of the frequency of a signal

To generate a series of reference signals at known frequency intervals

To display all frequency components of a transmitted signal

To provide a signal source at a very accurate frequency

E7F12: What alternate method of determining frequency, other than by directly counting input pulses, is used by some frequency counters?

Period measurement

GPS averaging

Prescaling

D/A conversion

E7F13: What is an advantage of a period-measuring frequency counter over a direct-count type?

It provides improved resolution of signals within a comparable time period

It can run on battery power for remote measurements

It does not require an expensive high-precision time base

It can directly measure the modulation index of an FM transmitter

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