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NAVEDTRA 14182

WAVE PROPOGATION, TRANSMISSION LINES, AND ANTENNAS

QuestionAnswer
Which two basic fields are associated with every antenna? induction and radiation
Which field is associated with the energy stored in the antenna? induction
Which type of antenna has an electrical length equal to half the wavelength of the signal being transmitted? half-wave
What is an energy wave called that is generated by a transmitter? radio wave
What is the basic shape of the wave generated by a transmitter? sine wave
The frequencies falling between 3kHz and what are called radio frequencies since they are commonly used in radio communications? 300GHz
The usable radio frequency range is roughly 10kHz to what? 100GHz
What is the VLF frequency range? 3 to 30kHz
What is the LF frequency range? 30 to 300kHz
What is the MF frequency range? 300 to 3000kHz
What is the HF frequency range? 3 to 30 MHz
What is the VHF frequency range? 30 to 300MHz
What is the UHF frequency range? 300 to 3000MHz
What is the SHF frequency range? 3 to 30GHz
What is the EHF frequency range? 30 to 300GHz
Any frequency that is a whole number multiple of a smaller basic frequency is known as what property of that basic frequency? Harmonic
What is the property of a radio wave which is simply the amount of time required for the completion of one full cycle? period
What is the space called occupied by one full cycle of a radio wave at any given time? wavelength
Where must the receiving antenna be located for maximum absorption of energy from the electromagnetic fields? plane of polarization
Troposphere, stratosphere, along with what else are the three separate regions or layers that the Earth's atmosphere is divided into? ionosphere
Which atmosphere layer has relatively little effect on radio waves because it is a relatively calm region with little or no temperature changes? stratosphere
What is the most important region of the atmosphere for long distance point-to-point communications? ionosphere
What are the two principle ways in which electromagnetic (radio) energy travels from a transmitting antenna to a receiving antenna? ground and sky waves
Which frequency band is used for sky wave propagation? high frequency (HF)
What is the process known as of upsetting electrical neutrality? ionization
What occurs when the free electrons and positive ions collide with each other? recombination
How many layers is the ionosphere composed of? 3
Each ionospheric layer has a maximum frequency at which radio waves can be transmitted vertically and refracted back to earth which is known as what? absorption
In what practice are two transmitters and two receivers used, each pair tuned to a different frequency, with the same information being transmitted simultaneously over both frequencies? frequency diversity
There is little natural interference above what frequency? 30MHz
What are responsible for variations in the ionization level of the ionosphere? sunspots
Long distance propagation of HF radio waves is almost totally "blanked out" when what occurs? sudden ionospheric disturbance (SID)
For a given angle of incidence and time of day, there is maximum frequency that can be used for communications between two given locations. What is this frequency called? maximum usable frequency (MUF)
Fog can cause serious attenuation by absorption at frequencies above what? 2 GHz
What is the condition when layers of warm air are formed above layers of cool air known as? temperature inversion
As the lowest region of the earth's atmosphere, the troposphere extends from the earth's surface to a height of slightly over how many miles? 7 mi
What region does virtually all weather phenomena occur in? troposphere
The usable frequency range for tropospheric scattering is from about 100MHz to what? 10GHz
A correctly designed tropospheric scatter circuit will provide highly reliable service for distances ranging from 50 miles to how many miles? 500 mi
Which device is designed to guide electrical energy from one point to another? transmission line
Which type of line is most often used for power lines, rural telephone lines, and telegraph lines? two-wire open
Which type of line consists of two insulated wires twisted together to form a flexible line without the use of spacers? twisted pair
Leakage caused by the condensation of moisture is prevented in some rigid line applications by the use of what? inert gas
The radius of bends in the waveguide must measure greater than how many wavelengths at the operating frequency of the equipment to avoid excess attenuation? two
Line losses may be any of three types- radiation/induction, dielectric, and what else? copper loss
Copper losses can be minimized and conductivity increased in an RF line by plating the line with what? silver
Which type of losses occur because some magnetic lines of force about a conductor do not return to the conductor when the cycle alternates? radiation loss
What determines the amount of current that can flow when a given voltage is applied to an infinitely long line? characteristic impedance
The characteristic impedance of lines in actual use normally lies between 50 and how many ohms? 600 ohms
When a transmission line is "short" compared to the length of the radio frequency waves it carries, the opposition presented to the input terminals is determined primarily by what? load impedance
If a line is not terminated in characteristic impedance, what is it said to be? finite
What are voltages called that are moving toward the receiving end of the line? incident voltages
Which type of line has no standing waves of current and voltage? nonresonant
What is the ratio of maximum voltage to minimum voltage on a line called? VSWR
What are hollow metal tubes used to transfer energy from one point to another? waveguides
Which two basic classifications are most practical transmitting antennas divided into? Hertz and Marconi
Which type of antennas operate with one end grounded and are mounted perpendicular to the earth or to a surface acting as a ground? Marconi
Hertz antennas are generally used for frequencies above what? 2 MHz
Which three parts does a complete antenna system consist of? coupling device, feeder, and antenna
What is defined as a conductor or group of conductors used either for radiating electromagnetic energy into space or for collecting it from space? antenna
What it the interchangeability of the same antenna for transmitting and receiving known as? reciprocity
Which frequencies is sky-wave transmission used? high frequency
Which type of polarization is used by VHF and UHF transmissions? horizontal
What is the useful part of the transmitter's signal? radiated energy
What it a plot of the radiated energy from an antenna? radiation pattern
What is it known as when antenna sources radiate energy equally in all directions? isotropic radiation
Which type of radiators emit stronger radiation in one direction than in another? anisotropic
What is used to indicate directions of minimum radiation? null
The electrical length of any antenna wire can be increased or decreased by what way? loading
What is the basic unit from which many complex antennas are constructed? half-wave antenna
What term is used to indicate an antenna that is very short compared with the wavelength of the operating frequency? doublet
What is the simplest form of a practical antenna? doublet
What type of antenna is the shortest antenna that can be used in free space? 1/2 wavelength
What is an ordinary half-wave antenna that has one or more additional conductors connected across its ends? folded dipole
What is a parasitic element referred to as when it operates to reinforce energy coming from the driver toward itself? director
What is a parasitic element referred to as if it is placed so it causes maximum energy radiation in a direction away from itself and toward the driven element? reflector
What designates an array in which the direction of maximum radiation is perpendicular to the plane containing these elements? broadside array
What type of array is it when all the elements lie in a straight line with no radiation at the ends of the array? collinear
What type of array is it when the principle direction of radiation is along the plane of the array and perpendicular to the elements? end-fire
What is an antenna that is a wavelength or longer at the operating frequency? long-wire
What is a horizontal, long-wire antenna designed especially for the reception ad transmission of low frequency, vertically polarized ground waves? beverage antenna
What is a half-wave radiator with a reflector? corner-reflector antenna
What is one of the most popular fixed-station antennas because it is very useful in point-to-point communications? rhombic
What is the heating of an insulating material by placing it in a high frequency electric field? dielectric heating
What parts of the human body are highly susceptible to dielectric heating? eyes
What is the area of radiation pattern that is covered by radiation? lobe
Created by: nng7294