# Extra Class Exam Question Pool

effective 7/01/2016 thru 6/29/2020

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

2016-E9D: Directional antennas: gain; Yagi Antennas; losses; SWR bandwidth; antenna efficiency; shortened and mobile antennas; RF Grounding

2016-E9D01: How does the gain of an ideal parabolic dish antenna change when the operating frequency is doubled?

Gain increases by 6 dB

Gain does not change

Gain is multiplied by 0.707

Gain increases by 3 dB

2016-E9D02: How can linearly polarized Yagi antennas be used to produce circular polarization?

Arrange two Yagis perpendicular to each other with the driven elements at the same point on the boom fed 90 degrees out of phase

Stack two Yagis fed 90 degrees out of phase to form an array with the respective elements in parallel planes

Stack two Yagis fed in phase to form an array with the respective elements in parallel planes

Arrange two Yagis collinear to each other with the driven elements fed 180 degrees out of phase

2016-E9D03: Where should a high Q loading coil be placed to minimize losses in a shortened vertical antenna?

Near the center of the vertical radiator

As low as possible on the vertical radiator

As close to the transmitter as possible

At a voltage node

2016-E9D04: Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance?

To minimize losses

To swamp out harmonics

To maximize losses

To minimize the Q

2016-E9D05: What is a disadvantage of using a multiband trapped antenna?

It radiates the harmonics and fundamental equally well

It is too sharply directional at lower frequencies

It must be neutralized

2016-E9D06: What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?

It is decreased

It is increased

No change occurs

It becomes flat

Lower Q

Greater structural strength

Higher losses

2016-E9D08: What happens as the Q of an antenna increases?

SWR bandwidth decreases

SWR bandwidth increases

Gain is reduced

More common-mode current is present on the feed line

2016-E9D09: What is the function of a loading coil used as part of an HF mobile antenna?

To cancel capacitive reactance

To increase the SWR bandwidth

To lower the losses

To lower the Q

2016-E9D10: What happens to feed point impedance at the base of a fixed length HF mobile antenna as the frequency of operation is lowered?

The radiation resistance decreases and the capacitive reactance increases

The radiation resistance decreases and the capacitive reactance decreases

The radiation resistance increases and the capacitive reactance decreases

The radiation resistance increases and the capacitive reactance increases

2016-E9D11: Which of the following types of conductors would be best for minimizing losses in a station's RF ground system?

A wide flat copper strap

A resistive wire, such as spark plug wire

A cable with six or seven 18 gauge conductors in parallel

A single 12 gauge or 10 gauge stainless steel wire

2016-E9D12: Which of the following would provide the best RF ground for your station?

An electrically short connection to 3 or 4 interconnected ground rods driven into the Earth

A 50 ohm resistor connected to ground

An electrically short connection to a metal water pipe

An electrically short connection to 3 or 4 interconnected ground rods via a series RF choke

2016-E9D13: What usually occurs if a Yagi antenna is designed solely for maximum forward gain?

The front-to-back ratio decreases

The front-to-back ratio increases

The frequency response is widened over the whole frequency band

The SWR is reduced

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