24 Questions
What is the main advantage of the two-hole directional coupler?
Low directional coupling
What is the best device to couple a coaxial line to a parallel-wire line?
Balun
What is the name of the method used to determine antenna impedance?
Smith chart
What type of antenna has a unity gain?
Isotropic
What is the velocity factor of a transmission line?
The velocity of the wave on the transmission line divided by the velocity of light in a vacuum
What type of transmission line consists of two conductors that have equal resistance per unit length?
Balanced line
What does EIRP stand for?
Effective isotropic radiated power
Which of the following is not a common transmission line impedance?
120 Ω
What is the smallest beam of a satellite antenna's radiation pattern?
Spot beam
What is the region in front of a parabolic antenna?
All of these
What is the relationship between the characteristic impedance of the line (Zo) and the load impedance (Zl) for maximum absorption of power at the antenna?
Zo = ZL
What type of antenna can only receive a television signal?
TVRO
What determines the characteristics of a transmission line?
Physical dimensions
What is the standing-wave ratio (SWR) when a 50 Ω coax is connected to a 73 Ω load?
1.46
What is the radiation pattern of a discone?
Omnidirectional
What is the product of the power supplied to an antenna and its gain relative to a half-wave dipole?
ERP
What is the measure of superiority of a material over a vacuum as a path of magnetic lines of force?
Permeability
What is the name of the transmission line that uses ground return?
Grounded line
What is the characteristic impedance of a transmission line independent of?
Length
What is the most commonly used transmission line?
Coax
What happens when the terminating impedance is exactly equal to the characteristic impedance of the transmission line?
The return loss is zero
What is the permeability of free space equal to?
1.257 x 10-6 henry/meter
What is the impedance of a balance 4-wire with a diameter of 0.25cm and spaced 2.5 cm apart using an insulator with a dielectric constant of 2.56?
75 ohms
What is the impedance of the matching section when matching a 73-ohm antenna to a 600 ohm polyethylene coaxial feeder line?
209.28 ohms
Study Notes
Antennas and Transmission Lines
- Circular polarization is a type of antenna polarization.
Antenna Impedance and Radiation Pattern
- Unity gain antenna is a half-wave dipole.
- EIRP stands for Effective Isotropic Radiated Power.
- Spot beam is the smallest beam of a satellite antenna's radiation pattern.
- A region in front of a parabolic antenna is known as the Fresnel zone.
- A TVRO is a type of antenna that can only receive a television signal.
- Radiation pattern of a discone is omnidirectional.
- Major lobe radiation refers to the concentration of radio waves in the direction of the signal emitted by a directional antenna.
Antenna Arrays and Components
- Reflector and director of an antenna array are considered parasitic elements.
- The product of the power supplied to the antenna and its gain relative to a half-wave dipole in a given direction is known as ERP.
Antenna Design and Characteristics
- Adding C in series or top loading can make an antenna physically long electronically short.
- The capture area of an antenna is directly proportional to the wavelength squared.
- Velocity factor of a transmission line is the ratio of the velocity of the wave on the transmission line to the velocity of light in a vacuum.
Transmission Lines
- A balun is used to couple a coaxial line to a parallel-wire line.
- The velocity factor of a transmission line is the ratio of the velocity of the wave on the transmission line to the velocity of light in a vacuum.
- A balanced line consists of two conductors with equal resistance per unit length.
- Common transmission line impedances include 50 Ω, 75 Ω, and 120 Ω.
- For maximum absorption of power at the antenna, the characteristic impedance of the line (Zo) should be equal to the load impedance (Zl).
Transmission Line Characteristics
- Twin lead is also referred to as an open pair.
- The standing-wave ratio is a ratio expressing the percentage of incident voltage reflected on a transmission line.
- Termination refers to the load connected to the output end of a transmission line.
Electrical Properties of Materials
- Permeability is a measure of a material's superiority over a vacuum as a path for magnetic lines of force.
- The permeability of free space is 1.257 x 10-6 henry/meter.
Common Transmission Lines
- Coaxial cable is the most commonly used transmission line.
- The characteristic impedance of a transmission line does not depend on its length.
Test your knowledge of antenna and propagation concepts, including impedance, polarization, and gain. Covers topics like EIRP and isotropic radiated power.
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