NAVEDTRA 14182A Module 10 Chapter 3 Flashcards
What connecting link is used to transfer energy from a radio transmitter to its
antenna located on the mast of a ship?
Transmission line
What term is used for the end of the transmission line that is connected to a
transmitter?
Input end, generator end, transmitter end, sending end, and source
What term is used for the end of the transmission line that is connected to an
antenna?
Output end, receiving end, load end and sink
List the five types of transmission lines in use today
Parallel two-wire, twisted pair, shielded pair, coaxial line and waveguide.
Name two of the three described uses of a two-wire open line
Power lines, rural telephone lines, and telegraph lines.
What are the two primary disadvantages of a two-wire open line?
High radiation losses and noise pickup.
What type of transmission line is often used to connect a television set to its antenna?
Twin lead
What is the primary advantage of the shielded pair?
The conductors are balanced to ground.
What are the two types of coaxial lines in use today?
Air coaxial (rigid) and solid coaxial (flexible).
What is the chief advantage of the air coaxial line?
The ability to minimize radiation losses
List the three disadvantages of the air coaxial line.
Expensive to construct, must be kept dry, and high frequency losses limit the
practical length of the line.
List the two common types of waveguides in use today
Cylindrical and rectangular.
What are the three types of line losses associated with transmission lines?
Copper, dielectric, and radiation
Losses caused by skin effect and the I 2
R (power) loss are classified as what type of
loss?
Copper losses
What types of losses cause the dielectric material between the conductors to be
heated?
Dielectric losses.
What are two of the three physical factors that determine the values of capacitance
and inductance of a transmission line?
(1) Type of line used, (2) dielectric in the line, and (3) length of line
A transmission line is said to have distributed constants of inductance, capacitance,
and resistance along the line. What units of measurement are used to express these
constants?
Inductance is expressed in microhenrys per unit length, capacitance is expressed
in picofarads per unit length, and resistance is expressed in ohms per unit length
Describe the leakage current in a transmission line and in what unit it is expressed
The small amount of current that flows through the dielectric between two wires
of a transmission line and is expressed in micromhos per unit length
ll the power sent down a transmission line from a transmitter can be transferred to
an antenna under what optimum conditions?
When the characteristic impedance of the transmission line and the load
impedance are equal.
What symbol is used to designate the characteristic impedance of a line, and what
two variables does it compare?
Z0 and it is the ratio of E to I at every point along the line.
What is the range of the characteristic impedance of lines used in actual practice?
Between 50 and 600 ohms
Two types of waves are formed on a transmission line. What names are given to
these waves?
Incident waves from generator to load. Reflected waves from load back to
generator
On an open-ended transmission line, the voltage is always zero at what distance
from each end of the line?
One-fourth the distance from each end of the line
A nonresonant line is a line that has no standing waves of current and voltage on it
and is considered to be flat. Why is this true?
The load impedance of such a line is equal to Z0.
On an open line, the voltage and impedance are maximum at what points on the
line?
Even quarter-wave points (1/2
At what point on an open-circuited rf line do voltage peaks occur?
At 1/2 wavelength from the end and at every 1/2 wavelength along the line
What is the square of the voltage standing-wave ratio called?
Power standing-wave ratio (pswr)
What does vswr measure?
The existence of voltage variations on a line.
