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38 Cards in this Set

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The ratio of voltage to current(Ein/Iin) at the input end is known as the?
INPUT IMPEDANCE (Zin).
The ratio of voltage to current at the output (Eout/Iout) end is known as the?
OUTPUT IMPEDANCE (Zout).
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
source
What term is used for the end of the transmission line that is connected to an antenna?
Output end
receiving end
load end
sink
This line consists
of two wires that are generally spaced from 2 to 6 inches apart by insulating spacers. This type of line is
most often used for power lines, rural telephone lines, and telegraph lines
TWO-WIRE OPEN LINE
2 wire line advantages
simple construction
2 wire line disadvantages
high radiation losses electrical noise pickup because of the lack of shielding
essentially the same as the two-wire open line except that uniform spacing is
assured by embedding the two wires in a low-loss dielectric
TWO-WIRE RIBBON (TWIN LEAD)
consists of two insulated wires twisted together to form a flexible line without the use of spacers
TWISTED PAIR
It is not used for transmitting high frequency because of the?
high dielectric losses that occur in the rubber
insulation
consists of parallel conductors separated from each
other and surrounded by a solid dielectric. The conductors are contained within a braided copper tubing
that acts as an electrical shield
SHIELDED PAIR,
SHIELDED PAIR advantage
conductors are balanced to ground
consists of a central, insulated wire (inner conductor) mounted inside a tubular
outer conductor
rigid coaxial line
advantage of the rigid line is its
ability to minimize radiation losses
rigid line has the following disadvantages:
(1) it is expensive to construct
(2) it must be kept dry
to prevent excessive leakage between the two conductors
(3) high-frequency losses
List the two common types of waveguides in use today.
Cylindrical and rectangular
I2R LOSS
copper loss
Whenever current flows through one of these conductors, some energy is dissipated in the form of
heat. This heat loss is a
POWER LOSS
Copper losses can be minimized and conductivity increased in an rf line by plating the line with?
silver
result from the heating effect on the dielectric material between the conductors
DIELECTRIC LOSSES
occur when the electromagnetic field about a conductor cuts through any nearby metallic object and a current is induced in that object
Induction losses
transmission line is transmission line is considered to be electrically short when its physical length is
short compared to a quarter wave length
A transmission line is electrically long when its physical length is
long compared to a quarter wavelength of the energy it is to carry
inductance which is expressed in
microhenrys per unit length
capacitance between the wires is usually expressed in
picofarads per unit length
Velocity of RF in free space?
300 X 10 6 meters per second
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.
Waveguide formula
velocity/frequency
CONDUCTANCE is the opposite of
resistance
The field associated with voltage is called the
ELECTRIC (E) FIELD
The field associated with current is called a
MAGNETIC (H) FIELD
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.
The characteristic impedance
of lines in actual use normally lies between?
50 and 600 ohms
At what points on an open endded transmission line does it act as a series-resonant circuit?
odd quarter wave points 1/4, 3/4 etc. E and Z min, I max
At what points on an open endded transmission line does it act as a Parallel-resonant circuit?
even quarter points. 1/2, 1, 3/2, ect. E and Z max, I min.