(D). The oscilloscope is the item of test equipment which contains horizontal and vertical channel amplifiers. This allows the equipment to evaluate wave forms of RF signals, and observe changes to the signal with varying signal voltages by plotting values on the X (horizontal) and Y (vertical) axes over time.

For more info see Wikipedia: Oscilloscope

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Both the digital voltmeter and oscilloscope can display different values of signal voltage, but complex waveforms can be hard to measure with a digital voltmeter—it's all just numbers. With a complex waveform often all you really want is to find a particular feature (like a peak), and that can be much easier by eyeballing it.

HINT: Oscilloscope is a complex word

"Oscilloscopes" show "Complex waves"

For more info see Wikipedia: Digital voltmeters, Oscilloscope

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An Oscilloscope is used to measure oscillations in an electrical signal -- in other words, it shows you the waveform of the signal. The keying waveform of a CW transmitter is the visual representation of the tone transmitted by the transmitter when you press the key, which can be seen on the oscilloscope screen.

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The attenuated RF output of the transmitter is connected to the vertical input of an oscilloscope when checking the RF envelope pattern of a transmitted signal. This allows you to check for signal distortions.

For more info see Wikipedia: Oscilloscope

**Memory tip: Output in the answer corresponds to Input in the question. ** KC3TGS

HINT: RF INPUT is in the question, RF OUTPUT is in the correct answer. KF4TYA

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Impedance is the measure of opposition to the flow of current. High input impedance is desired for a voltmeter because it limits, or decreases that loading on circuits being measured. Because of this the voltmeter only has to draw a very small amount of current from the circuit to be tested, and doesn't interfere with the normal flow and operation.

For more info see Wikipedia: Electrical impedance, Voltmeter

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(C). A digital voltmeter has an advantage over an analog meter because it has better precision for most uses. Digital voltmeters are easy to read if you are looking for a specific number level rather than trying to interpret the needle position on an analog scale. The analog meter may be more useful, however if you are looking for general up/down trends with being able to see the needle move in either direction, rather than focusing in on a specific value.

For more info see Wikipedia: Voltmeter

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(A). Close-in radio direction-finding is one use for a field strength meter. This device measures the strength of the electrical field given off by a transmitter. Higher values in one region over another indicate the direction of a source of RF energy. This meter along with a calibrated antenna is used for safety testing of RF energy outputs to make sure they are within maximum permissible exposure (MPE) limits.

For more info see Wikipedia: Field-strength meter

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A field-strength meter is used to monitor relative RF output when making antenna and transmitter adjustments. Using this meter along with a calibrated antenna let you test RF field put out by your transmitting equipment and antenna, to address both directional field issues, and levels of RF field exposure.

For more info see Wikipedia: Field-strength meter

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The field strength meter is useful for evaluating the radiation pattern of an antenna. If you see that the field strength is high in one specific direction, you know you have a good uni-directional / beam antenna and know to orient that point of field strength in the direction of your desired contact. If your signal strength is uniform in all directions around your antenna, it means that your antenna is omnidirectional.

For more info see Wikipedia: field-strength meter, Radiation pattern

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A directional wattmeter is used to determine the standing wave ratio, which is the relationship between the forward and reflected power.

Its easy to determine the "Direction" of a wave if you are "Standing in the wave"

For more info see Wikipedia: Standing wave ratio, wattmeter

Oversimplification: Most SWR meters will tell you your forward watts and your reverse/reflected watts, in both directions.

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(C). Both the antenna and feed line must be connected to an antenna analyzer when it is being used for SWR (standing wave ratio) measurements. This device helps to measure the effeciency of your antenna setup.

For more info see Wikipedia: Standing Wave Ratio, Antenna analyzer

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(B). When making measurements to evaluate an antenna system with an antenna analyzer, strong signals from nearby transmitters can affect the accuracy of the measurements. These extra signals can distort the ratio of forward to reflected power (SWR) being generated within your own system. You might get values much higher or lower than you expected, depending on the direction and strength of the competing signal.

For more info see Wikipedia: Antenna analyzer, Standing Wave Ratio

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The antenna analyzer is a device that measures the input impedance of an antenna system.

The Standing Wave Ratio (SWR) is a measure of impedance mismatch, which is why an antenna analyzer is used to figure it out.

If you have an antenna with a known impedance, then you can use the antenna analyzer to figure out the impedance of an unknown or unmarked coaxial cable.

Notice that none of the distractors have anything to do with impedance.

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When you are performing operations such as adjusting tuned circuits, an instrument with analog readout may be preferred over an instrument with a numerical digital readout.

This is because if you are looking for up or down trends, it can be much easier to compare the tuning adjustments with a greater up/down movement of the needle (going to a maximum/minimum or approaching a center line) rather than trying to interpret how the numerical values correspond to the tuning operation.

Hint: Instrument <-> Tuned

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A two-tone test measures the linearity of an SSB signal.

A perfectly linear transmitter would produce those two tones—and only those two tones.

The more non-linear the transmitter, the more harmonics are generated, producing additional signal content at frequencies other than the two input tones.

The test itself consists of sending two tones that are not harmonically related into the transmitter. The tones are produced with equal power levels, so the only variable is frequency. The output can then be examined using an oscilloscope or spectroscope to see what other signals are being produced at other frequencies.

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A two-tone test uses two non-harmonically related audio signals to test the linearity of signal amplitude in an SSB transmission. The two tones of equal power are put into the microphone input and the waveforms are examined for linearity using an oscilloscope.

Hint: The two [tones] are "related".

Two-tone test

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