(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

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

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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 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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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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When adjusting a circuit connected to an analog meter, you can see the indicator moving to a higher or lower reading - it's moving up or down.

When you're adjusting for a maximum or minimum value, you only have to look at whether it's moving up or down - you don't have to interpret a digital display of a number to get a sense of whether it's increasing or decreasing.

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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.

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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Antenna analyzers transmit a very weak signal and measures the SWR of that signal.

A strong signal from a nearby transmitter can enter the antenna under test and be reflected to the analyzer, confusing the SWR reading.

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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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