$A$ $100\,m$ long antenna is mounted on a $500\,m$ tall building. The complex can become a transmission tower for waves with $\lambda$ (approx) ........ $m$.

If a message signal of frequency $10 kHz$ and peak voltage $12 V$ is used to modulate a carrier wave of frequency $1 MHz$, the modulation index is $0.6$. To make the modulation index $0.75$, the carrier peak voltage should be

The range of frequency bands used for standard $AM$ broadcast is

$A$ baseband signal of $3.5\, MHz$ frequency is modulated with a carrier signal of $3.5\, GHz$ frequency using amplitude modulation. What should be the minimum size of antenna required to transmit the modulated signal?

The maximum frequency of transmitted radio waves above which the radio waves are no longer reflected back by the ionosphere is . . . . . . ($N=$ maximum electron density of the ionosphere, $g=$ acceleration due to gravity).

The frequency range suitable for beyond-the-horizon communication using sky waves is: