In the process of modulation,the audio waves are called ...........

The frequency range for commercial $FM$ radio broadcasting is .......

$A$ $TV$ transmission antenna is $40 \ m$ tall. How much service area can it cover if the receiving antenna is at the ground level? (Radius of the Earth $= 6400 \ km$)

$A$ $500\, Hz$ modulating voltage fed into an $FM$ generator produces a frequency deviation of $2.25\, kHz$. If the amplitude of the voltage is kept constant but the frequency is raised to $6\, kHz$,then the new frequency deviation will be.......$kHz$.

An amplitude modulated wave is represented by $c_m(t)= 10[1+0.6 \sin (1250 t)] \sin (10^8 t)$. Then the modulation index is

The characteristic impedance of a coaxial cable is typically ...... .