The bandwidth of a coaxial cable system is approximately........ $MHz$.

To radiate a wave of frequency $1 \text{ kHz}$ efficiently,what should be the minimum length of the antenna in $km$?

The amplitude of the upper and lower sidebands of an $A.M.$ wave,where a carrier signal with frequency $11.21 \, MHz$ and peak voltage $15 \, V$ is amplitude modulated by a $7.7 \, kHz$ sine wave of $5 \, V$ amplitude,are $\frac{a}{10} \, V$ and $\frac{b}{10} \, V$ respectively. Then the value of $\frac{a}{b}$ is $....$

For sky wave propagation,the radio waves must have a frequency range in between

The process of superimposing a message signal on a high-frequency carrier wave is called:

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