radio wave characteristics Flashcards
(24 cards)
type of wave that ccarries radio signals between transmitting and receiving stations
electromagnetic
unit of frequency
hertz, one cycle per second
how fast does a radio wave travel
speed of light
wavelength
distance a radio wave travels during one coplete cycle
relationship between frequency and wavelength
as frequency increases, wavelength decreases
the approximate wavelength
used to identify frequency bands
what is RF
radio frequency signals
HF vs VHF vs UHF
hf high frequency, 3-30 MHz
vhf very high frequency 30-300
uhf ultrahigh frequency 300-3000
why cant you hear uhf signals outside your coverage area
they arent reflected by the ionosphere
radio horizon
distance at which radio signals between two points are effectively blocked by the curvature of the earth
multi path istortion
random reflections can cause frequencies to become out of phase
whats most effective form inside buildings and why
UHF bands, shorter wavelength allows them to penetrate structure of buildings
knife edge propagation
signals are partially refracted around solid objects exhibitng shar edges
polarization
orientation of electric field
vertical vs horizontal antenna polarizationn
horizontal is used for long distance weaek signals
picket fencing
rapid fluttering sound sometimes heard form mobile stations that are moving while transmitting
how are nhf signals received over long distances
they are refracted from a sporadic e layer
what happens to vhf signals bounced off aurora
rapid fluctuations in strength, distortion
best band for meteor propagation
6 meters
tropospheric scater
responsible for over the horizon vhf uhf ranges, caused by temperature inversionsn
HF propagation
enables propagation of radio signnals around the world
what meters are best dudring peak of sunspot cycle
6 to 10
fading phenomena
random combining of signals arriving via different path lengths, from hf
is it important to polarize with hf
no because signas become elliptically polarized from the atmosphere
