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Subelement L
Installation, Maintenance & Repair
Section 75
Test Equipment
How is a frequency counter used?
  • To provide reference points on an analog receiver dial thereby aiding in the alignment of the receiver.
  • To heterodyne the frequency being measured with a known variable frequency oscillator until zero beat is achieved, thereby indicating the unknown frequency.
  • To measure the deviation in an FM transmitter in order to determine the percentage of modulation.
  • Correct Answer
    To measure the time between events, or the frequency, which is the reciprocal of the time.

How is a frequency counter used?

To measure the time between events, or the frequency, which is the reciprocal of the time.

It counts the number of cycles of oscillation, called pulses per second in a signal. To do so, it counts the number of times a signal hits a set trigger voltage setting in a period of time, generally zero, as the wave goes up and down.

See Fluke site for the article What is Frequency?

For more information, please see Wikipedia's article on Frequency counter

Also, see Electronics Notes for the article What is a Frequency Counter

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What is a frequency standard?
  • A well-known (standard) frequency used for transmitting certain messages.
  • Correct Answer
    A device used to produce a highly accurate reference frequency.
  • A device for accurately measuring frequency to within 1 Hz.
  • A device used to generate wide-band random frequencies.

What is a frequency standard?

A device used to produce a highly accurate reference frequency.

See Fluke site for the article What is Frequency?

For more information, please see Wikipedia's article on Frequency counter and Frequency standard

Also, see Electronics Notes for the article What is a Frequency Counter

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What equipment may be useful to track down EMI aboard a ship or aircraft?
  • Fluke multimeter.
  • An oscilloscope.
  • Correct Answer
    Portable AM receiver.
  • A logic probe.

What equipment may be useful to track down EMI aboard a ship or aircraft?

Portable AM receiver.

YouTube Video: View Using an AM Radio to Detect EMI

Also, see Tektronix site for the article A 3-Step Process to Identify Electromagnetic Interference (EMI)

And Compliance Engineering for the article The Definitive Guide For Detecting Electromagnetic Interference

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On an analog wattmeter, what part of the scale is most accurate and how much does that accuracy extend to the rest of the reading scale?
  • Correct Answer
    The accuracy is only at full scale, and that absolute number reading is carried through to the rest of the range. The upper 1/3 of the meter is the only truly calibrated part.
  • The accuracy is constant throughout the entire range of the meter.
  • The accuracy is only there at the upper 5% of the meter, and is not carried through at any other reading.
  • The accuracy cannot be determined at any reading.

On an analog wattmeter, what part of the scale is most accurate and how much does that accuracy extend to the rest of the reading scale?

The accuracy is only at full scale, and that absolute number reading is carried through to the rest of the range. The upper 1/3 of the meter is the only truly calibrated part.

See Wikipedia's article on Wattmeter.

For more information, please RF Cafe site for the article on How to Interpret Standard Ratings for Meter Accuracy

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Which of the following frequency standards is used as a time base standard by field technicians?
  • Quartz Crystal.
  • Correct Answer
    Rubidium Standard.
  • Cesium Beam Standard.
  • LC Tank Oscillator.

Which of the following frequency standards is used as a time base standard by field technicians?

Rubidium Standard.

This is the rubidium atomic clock, using rubidium-87 electron transition, to generate frequency which is used as the frequency standard.

See Wikipedia's article on Rubidium standard

Also see Stanford Research Systems site for the article entitled Rubidium Oscillator PRS10 — Low phase noise Rb oscillator

YouTube: View EEVblog channel for the Rubidium Frequency Standard

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Which of the following contains a multirange AF voltmeter calibrated in dB and a sharp, internal 1000 Hz bandstop filter, both used in conjunction with each other to perform quieting tests?
  • Correct Answer
    SINAD meter.
  • Reflectometer.
  • Dip meter.
  • Vector-impedance meter.

Which of the following contains

  • a multirange AF voltmeter calibrated in dB and
  • a sharp, internal 1000 Hz band stop filter,
  • both used in conjunction with each other

to perform quieting tests?

SINAD meter.

From badwolf.j.: SINAD: Signal-to-Noise and Distortion


The SINAD meter measure imperfection of the radio wave signal due to other other frequencies accompanying the signal, commonly called "noise."

By measuring the clear signal to noise one, it can be used to determine the ability of a radio receiver to distinguish between a clear signal and one with noise, called sensitivity of the receiver.

See Wikipedia's article on SINAD and also article on Signal-to-noise ratio

For more information, please see Electronics Notes article on What is SINAD: SINAD measurements

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