NAVEDTRA 14182A Ch2 Flashcards
Which 2 basic fields are associated with every antenna
Induction
Radiation
In an antenna, which field is associated with energy stored
Induction
Which type of antenna has an electrical length equal to HALF the WAVE of the signal being transmitted?
Half wave antenna
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
(Radio wave)
Sine wave
What is the NUMBER OF CYCLES of a sine wave that are completed in 1 second known as
Frequency
Between 3KHz and _____ are commonly used for radio communications
300GHz
Useable radio frequencies range roughly through 10KHz to _____.
100GHz
Frequency ranges: VLF- LF- MF- HF- VHF- UHF- SHF- EHF-
Very Loud Music Has Very Unusual Side Effect
VLF- 3 - 30 KHZ LF- 30- 300KHz MF- 300KHz - 3 MHz HF- 3MHz - 30MHz VHF-30 - 300MHz UHF- 300MHz - 3GHz SHF- 3 - 30GHz EHF- 30-300GHz
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 1 full cycle of a radio wave at any given instant
Wavelength
What is the speed of light
186,000 miles per second
Where must the receiving antenna be located for maximum absorption of energy from the electromagnetic fields
Plane of polarization
The TROPOSPHERE extends from the surface of the earth to a height of ________ miles at the equator
11.3 miles
The TROPOSPHERE extends from the surface of the earth to a height of ________ miles at the north and South Pole
3.7 miles
Which atmosphere layer has relatively NO EFFECT on radio waves because it is a calm region with little to no temp change
Stratosphere
The ionosphere extends upward from about 31.1 miles to a height of about how many miles above the earths surface
250 miles
Which frequency band is used for sky wave propagation
HF
What is the process know as upsetting electrical neutrality
Ionization
What occurs when free electrons and positive ions COLLIDE with each other
Recombination
How many layers is the ionosphere composed of
3
1) D
2) E
3) F.
a) f1
b) f2
What is the DISTANCE from the transmitter to the point where the sky wave first returns to the earth
Skip distance
What results in the loss of energy of a radio wave and has a pronounced effect on both the strength of the signal received and the ability to communicate over a long distance
Absorption
Fading on ionospheric circuits is mainly a result of what?
Multi path propagation
There is little natural interference above what frequency
Above HF
Above 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
“SID”
Sudden ionospheric disturbance
Rain drops cause greater attenuation by scattering then by absorption at frequencies above what
100 MHz
Fog can cause serious attenuation by absorption at frequencies above what
2GHZ
What is the condition when layers of warm air are formed above layers of cool air is known as
Temperature inversion
What region does virtually all weather phenomena occur in
Troposphere
