Login or Register for FREE!
Subelement G4
Amateur Radio Practices
Section G4E
HF mobile radio installations; alternative energy source operation
What is the purpose of a capacitance hat on a mobile antenna?
  • To increase the power handling capacity of a whip antenna
  • To allow automatic band changing
  • Correct Answer
    To electrically lengthen a physically short antenna
  • To allow remote tuning

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."

Last edited by gconklin. Register to edit

Tags: arrl chapter 7 arrl module 28

What is the purpose of a corona ball on an HF mobile antenna?
  • To narrow the operating bandwidth of the antenna
  • To increase the "Q" of the antenna
  • To reduce the chance of damage if the antenna should strike an object
  • Correct Answer
    To reduce RF voltage discharge from the tip of the antenna while transmitting

(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.

Last edited by sinbad909. Register to edit

Tags: arrl chapter 7 arrl module 28

Which of the following direct, fused power connections would be the best for a 100 watt HF mobile installation?
  • Correct Answer
    To the battery using heavy-gauge wire
  • To the alternator or generator using heavy-gauge wire
  • To the battery using resistor wire
  • To the alternator or generator using resistor wire

(A). The best direct, fused power connection for a 100-watt HF mobile installation is a connection to the battery using heavy gauge wire. The auxiliary outlet should not be used for a 100-watt mobile radio. It cannot handle the current required. Power connections should be made directly to battery terminals, with fuses installed on the leads as close to the battery as feasible.

Last edited by N8GCU. Register to edit

Tags: arrl chapter 5 arrl module 21

Why is it best NOT to draw the DC power for a 100 watt HF transceiver from a vehicle's auxiliary power socket?
  • The socket is not wired with an RF-shielded power cable
  • Correct Answer
    The socket's wiring may be inadequate for the current drawn by the transceiver
  • The DC polarity of the socket is reversed from the polarity of modern HF transceivers
  • Drawing more than 50 watts from this socket could cause the engine to overheat

(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.

Last edited by N8GCU. Register to edit

Tags: arrl chapter 5 arrl module 21

Which of the following most limits an HF mobile installation?
  • "Picket fencing"
  • The wire gauge of the DC power line to the transceiver
  • Correct Answer
    Efficiency of the electrically short antenna
  • FCC rules limiting mobile output power on the 75-meter band

Keyword: most

Picket fencing relates generally to weak FM signals. While there are FM operations on the 10-meter band, this would not impact any other HF band.

The wire gauge of the transceiver's power line could impact maximum power output, but this is a variable highly in the control of the radio owner.

There isn't a FCC rule limiting mobile output power.

HF antennas are often electrically short, and are highly inefficient. This is an impact on all HF bands.

Last edited by abartlett. Register to edit

Tags: arrl chapter 5 arrl module 21

What is one disadvantage of using a shortened mobile antenna as opposed to a full-size antenna?
  • Short antennas are more likely to cause distortion of transmitted signals
  • Short antennas can only receive circularly polarized signals
  • Correct Answer
    Operating bandwidth may be very limited
  • Harmonic radiation may increase

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.

Last edited by chicagoway. Register to edit

Tags: arrl chapter 7 arrl module 28

Which of the following may cause receive interference in a radio installed in a vehicle?
  • The battery charging system
  • The fuel delivery system
  • The vehicle control computer
  • Correct Answer
    All these choices are correct

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.

Last edited by kd2owc. Register to edit

Tags: arrl chapter 5 arrl module 21

What is the name of the process by which sunlight is changed directly into electricity?
  • Correct Answer
    Photovoltaic conversion
  • Photon emission
  • Photosynthesis
  • Photon decomposition

(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.

Last edited by N8GCU. Register to edit

Tags: arrl chapter 4 arrl module 15

What is the approximate open-circuit voltage from a fully illuminated silicon photovoltaic cell?
  • 0.02 VDC
  • Correct Answer
    0.5 VDC
  • 0.2 VDC
  • 1.38 VDC

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

Last edited by marvsherman419. Register to edit

Tags: arrl chapter 4 arrl module 15

What is the reason that a series diode is connected between a solar panel and a storage battery that is being charged by the panel?
  • The diode serves to regulate the charging voltage to prevent overcharge
  • Correct Answer
    The diode prevents self-discharge of the battery through the panel during times of low or no illumination
  • The diode limits the current flowing from the panel to a safe value
  • The diode greatly increases the efficiency during times of high illumination

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-.

Last edited by maurah29. Register to edit

Tags: arrl chapter 4 arrl module 15

Which of the following is a disadvantage of using wind as the primary source of power for an emergency station?
  • The conversion efficiency from mechanical energy to electrical energy is less than 2 percent
  • The voltage and current ratings of such systems are not compatible with amateur equipment
  • Correct Answer
    A large energy storage system is needed to supply power when the wind is not blowing
  • All these choices are correct

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.

Last edited by glitteribbon. Register to edit

Tags: arrl chapter 4 arrl module 15

Go to G4D Go to G5A