Antenna Theory and Design

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What is the effect of constructing a similar antenna on the other side of the conducting sheet?

It will reduce the antenna's performance

It will improve the antenna's performance

It will change the polarity of the antenna

It will not affect the antenna's performance in any way (correct)

What is the effect of removing the conducting sheet in the arrangement equivalent to the Hertz antenna?

It will reduce the antenna's performance

It will not have any effect (correct)

It will improve the antenna's performance

It will change the polarity of the antenna

How does the drive point impedance of the Hertz antenna compare to the Marconi antennas?

It is half as great

It is the same

It is four times as great

It is twice as great (correct)

How does the power absorbed by the Hertz antenna compare to the Marconi antennas?

It is twice as much Signup and view all the answers

What is the relationship between the currents in the Marconi antennas and the Hertz antenna?

The currents are the same Signup and view all the answers

What is the purpose of the conducting sheet in the Marconi antenna arrangement?

The conducting sheet has no purpose and can be removed without effect Signup and view all the answers

How is radiation achieved in the antenna setup?

By opening out the conductors and having currents in the same direction Signup and view all the answers

What is a half-wave dipole?

Two arms with a total length slightly less than half a wavelength Signup and view all the answers

Which of the following statements about the half-wave dipole is true?

It serves as a useful reference standard against which other antennas can be compared Signup and view all the answers

What does the voltage and current detector measure?

The electric and magnetic fields around the conductors Signup and view all the answers

What is the relationship between the magnetic field and the current in the conductor?

The magnetic field is directly proportional to the current Signup and view all the answers

What does the demonstration with the two conductors show?

It shows the production of expanded fields stretching away from the conductors Signup and view all the answers

What is the primary function of a transmission line in a radio system?

To convey power from the transmitter to the antenna Signup and view all the answers

Why is it important that the voltage and current on a transmission line be 'suitably balanced'?

To prevent the transmission line from radiating power Signup and view all the answers

What is the purpose of the 'feeders' mentioned in the text?

To connect the transmitter or receiver to the antenna Signup and view all the answers

Why does the voltage and current vary at different points along a transmission line?

Due to the inductance and capacitance of the line Signup and view all the answers

What is the purpose of properly designing a transmission line?

To minimize radiation from the line Signup and view all the answers

What is the simplest case of connecting a transmitter or receiver to an antenna?

Directly connecting the terminals Signup and view all the answers

What is the purpose of using half-wave and quarter-wave rods with lamps inserted at intervals?

To demonstrate the effects of capacitance and inductance on current distribution Signup and view all the answers

What is the primary difference between the T antenna and the inverted-L antenna demonstrated?

The T antenna produces more vertically polarized radiation, while the inverted-L produces more horizontally polarized radiation Signup and view all the answers

What is the primary benefit of using loading techniques when the antenna height is limited in relation to the wavelength?

It increases the radiation resistance, reducing power losses Signup and view all the answers

What happens to the drive point impedance and radiation resistance when the electrical length of an antenna is changed?

The drive point impedance and radiation resistance change, but the effects can be beneficial Signup and view all the answers

What is the primary cause of power losses in short antennas?

High currents due to low radiation resistance Signup and view all the answers

Which of the following statements is true about the demonstrations described in the text?

They focus on the effects of capacitance and inductance on antenna performance Signup and view all the answers

What is the purpose of the impedance transformation over a /4 feeder in an antenna?

To determine the impedance ratio and the rate of change of reactance with frequency in the antenna Signup and view all the answers

What is the 'characteristic impedance' of an antenna defined as?

$Z_o = \sqrt{(maximum R_d)(radiation resistance)}$ Signup and view all the answers

How can the characteristic impedance $Z_o$ of an antenna be altered?

Both (b) and (c) Signup and view all the answers

What is the expression that can be used to calculate the characteristic impedance $Z_o$ for a vertical round wire just above a perfectly conducting ground?

$Z_o = \left(\ln\left(\frac{h}{r}\right) - 1\right)$ Signup and view all the answers

What is the distinction between radiation resistance and the drive point impedance of an antenna?

Radiation resistance is defined at the point of maximum current, while drive point impedance is defined at the feed point Signup and view all the answers

What is the typical range of values for the characteristic impedance $Z_o$ of a vertical round wire antenna just above a perfectly conducting ground?

Between 230 and 650 ohms Signup and view all the answers