wireless commumiction - radio waves Flashcards
why are radio and microwaves used for cmonucachion over long distances
they do not get absorbed by the earth atosmthear unlike the ones in the middle of the em wave spectrum and hight frequency would be to dangerous to use.
why are short wave radio signals rasped at long dispense
they reflect of the ionosphere
why do you need to be in line of sight of tv and FM radio
they don’t bent round hills or go far through billings
why do longer wavs go ferver
they go longer distend because they can difraked around billings and hills so the receivers don’t hath to be in line of sight
why do shorter waves go lees ditensed
they carnet diffracted around hills so the receivers had to be in line of sight.
how dose refraction help waves travel therether
when a wave hits the ionosphere it can refracted back on to the earth.
what are ionised atoms
atoms that have gained of losted electrons.
what is multi multiplexing
where lots os signals are comprest into a single wave
ups and downs of DAB
ups - more stations multiplexing
downs - not as clear limited transmitter
