A "capacitance hat" is a device on the end of a mobile antenna which acts to electrically lengthen a physically short antenna. The device, usually made up of a ring, or an arrangement of rods, is used on the top of the antenna. The device increases the capacitance of the antenna, which causes it to act electrically "longer."

SILLY HINT: A "top hat" makes a short person look taller/longer.

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(D). A "corona ball" on a HF mobile antenna is used to reduce high voltage discharge from the tip of the antenna. The sharp tipped mobile antenna can discharge extra voltage that builds up as an electrical arc or coronal discharge. The corona ball device reduces the chance of forming such arcs.

Study Tip: Corona (virus) is a *transmitting" pandemic. Associate Corona with the word transmitting which appears in the correct answer.

Reduce corona voltage/hysteria by putting a ball/cap on it.

Definitely want to REDUCE covid.

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The best direct, fused power connection for a 100-watt HF mobile installation is a connection directly to the battery using heavy-gauge wire. This ensures the radio can handle the high current needed without causing voltage drops. Avoid using the auxiliary outlet, as it cannot handle the required power.

For setups with multiple power connections, it’s also a good idea to use a bus bar, preferably a radio/avionics bus bar, to safely distribute power to additional devices. This helps keep wiring organized and prevents overloading the battery terminals.

When connecting directly to the battery, take precautions to avoid corrosion by using a protective sealant on the terminals, and ensure the wiring is safely routed through grommets or protective sheaths to avoid damage. Also, fuses should be installed as close to the battery as possible on both the positive and negative leads.

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(B). It is best NOT to draw the DC power for a 100-watt HF transceiver from an automobile's auxiliary power socket because the socket's wiring may be inadequate for the current being drawn by the transceiver. Instead, the unit should be powered by connecting heavy gauge wire leads to the battery terminals, with fuses on the leads located as close to the battery as possible.

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(C). The antenna system is the factor which most limits the effectiveness of an HF mobile transceiver operating in the 75 meter band.

The main reason for this is the length limitation of mobile mounted antennas. A 1/4 wave antenna would be over 50 feet long, and you can't drive down the road with THAT on top of your car!

Because smaller fractional wavelength antennas must be used, usually with some type of inductive loading required, these antennas are not very efficient for HF operation in the 75 meter band.

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One disadvantage of using a shortened mobile antenna as opposed to a full size antenna is that operating bandwidth may be very limited. The fractional wave electrically short antennas have low impedances at the feed point and very narrow frequency ranges. Unfortunately, it just is not practical or safe to attach the length of antenna required for efficient transmitting, especially at HF frequencies.

Key: "limited antenna" a.k.a mobile, limited bandwith

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All of these choices are correct

Yes, the alternator ( battery charging system) can give off a whine. Yes, the fuel pump ( fuel delivering system) can give off a similar whine. Yes, the control computer can give off stray rf interference. So all of these choices are, indeed correct. All I can say is, modern vehicles were not designed for the average ham.

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(A). Photovoltaic conversion is the name of the process by which sunlight is changed directly into electricity. The "photo" refers to the light of the sun, and "voltaic" refers to power. This is how solar cells convert sunlight into electric current.

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The current standard modern, well-illuminated (full sun exposure) photovoltaic cell has an approximate open-circuit voltage of 0.5 Volts DC. These cells may also be known as solar or photoelectric cells. The maximum current that a photovoltaic cell can provide is dependent on the total surface area of the cell. Individual standard cells may be arranged together to form solar panels for larger power requirements.

For more info see Wikipedia: Solar cell

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A diode only lets current flow in one direction. The direction you want if you're collecting solar energy is from the solar panel to the battery. The diode will prevent the energy from going in the other direction when the battery has more energy than the solar panel (during the night or other periods of low light).

Silly Hint: A Diode is Directional, preventing a change of direction of current, and therefore preventing Discharge, all words beginning with D-I-.

Note: When a Zener diode is used to control voltage it does so with reverse polarity compared to a diode that would prevent energy from going to the panel. A Zener diode limits the voltage, but not the current nor the power.

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It's not that you can't use wind as a power source, it's that the wind doesn't always blow, so you'd need to be able to store huge amounts of power in case emergency strikes when it's not blowing.

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