Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
27 Cards in this Set
- Front
- Back
|
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. |
|
|
All 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.
|
|
|
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
|
|
|
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.
|
