(D). The term "NVIS" means as related to antennas - Near Vertical Incidence Sky wave

This refers to using antenna polarization to radiate signals at high vertical angles. Such signals allow for close distance communications using the "skip zone" but may be effective for avoiding local horizontal interferences.

For more info see Wikipedia: NVIS, or Near Vertical Incidence Skywave

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(B). An advantage of an NVIS antenna is high vertical angle radiation for working stations within a radius of a few hundred kilometers.

The radio signals are reflected in the "skip zone" of the atmosphere and allow for close distance communications where there may be interferences in the horizontal direction.

For more info see Wikipedia: NVIS, or Near Vertical Incidence Skywave

Quick mnemonic: NEAR Vertical reaches NEAR stations.

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NVIS is an acronym for Near Vertical Incidence Skywave. With this sort of antenna you want to be very close to the ground so that the signal bounces almost straight up.

proximity to the ground forces the majority of the radiation to go straight up —wikipedia

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The primary purpose of antenna traps is to permit multiband operation.

Resonant LC circuits are used in parallel to isolate sections of the antenna effectively changing the antenna's "electrical length". This allows the antenna to be used for several bands rather than one static wavelength.

SILLY HINT: (Plural) Antenna traps and multiple bands

For more info see Wikipedia: Antenna (radio)_Bandwidth

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The advantage of vertical stacking of horizontally polarized Yagi antennas is that it narrows the main lobe in elevation.

The resulting narrowing of the vertical width of the main lobe results in an increase in gain, with stronger received signals and less noise.

Suggest: 'vertical stacking', vertical - phrase for elevation

For more information see Wikipedia: Yagi antenna

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An advantage of a log periodic antenna is wide bandwidth.

In this type of multi-element directional antenna, the lengths of the elements and the spacing among them are both arranged in a log-periodic manner. This allows the antenna to be operated consistently over a large range of frequencies.

Hint: A log is wide.

For more info see Wikipedia: Log periodic antenna

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A log periodic antenna is described as one in which the length and spacing of the elements increases logarithmically from one end of the boom to the other.

The advantage of this type of antenna arrangement is that it allows operation over a wide range of frequencies, rather than one static frequency band.

Memorization aid: "log" in the question = "logarithmically" in the correct answer

The word "logarithmically" appears in 2 answers; For me better to remember "log" in the question = "log - boom" in the correct answer

For more info see Wikipedia: Log periodic antenna

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(B). The Beverage antenna is not used for transmitting because it has high losses compared to other types of antennas.

The Beverage antenna DOES make for a very effective and relatively inexpensive receiving antenna, however. It is highly directional, and so does not pick up a lot of noise or signals from unwanted directions.

For more info see Wikipedia: Beverage antenna

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An application for a Beverage antenna is directional receiving for low HF bands.

The Beverage antenna is not effective for transmitting but is a highly effective and relatively inexpensive antenna for the directional reception of radio signals. Its effectiveness is greatest for the lower frequency HF bands (7 MHz and lower).

It's not very portable due to its size.

Wikipedia: Beverage antenna QSL: Beverage antenna

Think Dr. Pepper is a beverage. "D"irectional "R"eceiving Helpful Hint: You Receive a Beverage

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(D). A Beverage antenna can be described as a very long and low directional receiving antenna.

The Beverage antenna is typically made of a wire from one-half to two wavelengths long. For some of the low HF band where this type of antenna is most effective this can be several hundred feet or longer! This unidirectional wire creates a very effective directional receiving antenna, greatly reducing unwanted noise from other signal directions. It is not effective for transmission due to high signal losses.

For more info see Wikipedia: Beverage antenna

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Since multiband antennas are designed to be resonant at many different frequencies, they are much less resistant to signals that come in on harmonics of the frequencies for which they are tuned. This can result in interference from harmonics that may not affect a single band antenna.

Silly hint: The battle of the bands had a poor harmonica player.

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