Ultra high frequency $(UHF)$ band stands for

The $T.V.$ transmission tower in Delhi has a height of $245 \ m$. The distance up to which the broadcast can be received (taking the radius of the earth to be $6.4 \times 10^6 \ m$) is .......... $km$.

If $E_c$ and $E_m$ are peak values of carrier and modulating signals,respectively,then for $100 \%$ modulation,

$A$ signal of frequency $10 kHz$ and peak voltage $10 V$ is used to amplitude modulate a carrier of frequency $1 MHz$ and peak voltage $20 V$. The side-band frequencies in $kHz$ are

$A$ carrier wave $v_{c}(t) = 160 \sin(2 \pi \times 10^{6} t) \text{ V}$ is made to vary between $V_{\max} = 200 \text{ V}$ and $V_{\min} = 120 \text{ V}$ by a message signal $v_{m}(t) = A_{m} \sin(2 \pi \times 10^{3} t) \text{ V}$. The peak voltage $A_{m}$ of the modulating signal is ..... .

The characteristic impedance of a coaxial cable is typically in the range of ..........