Explanation
Frequency modulation requires much wider channel (7 to 15 times) as compared to AM.
Following are the problems which are faced while transmitting audio signals directly,
(i) These signals axe relatively of short range.
(ii) If every body started transmitted these low frequency signals directly, mutual interference will render all of them ineffective.
(ill)Size of antenna required for their efficient radiation would be larger, i. e., about 75 km.
Remote sensing is the technique to collect information about an object in respect of its size, colour, nature, location, temperature etc. without physically touching
it. There arc some areas or locations which are inaccessible. So to explore these areas or locations, a technique known as remote sensing is used. Remote sensing is done through a satellite.
For satisfactory working of He-Ne laser, the ratio of helium to neon is 7 : 1.
The sky waves are the radiowaves of frequency between 2 MHz to 30 MHz. These waves can propagate through atmosphere and are reflected back the ionosphere of earth’s atmosphere.
Modulation is a process of superposing a low frequency audio signals (called modulating signal) on a high frequency radio wave called carrier wave.
In PWM (Pulse Width Modulation), which is also called PDM (Pulse Duration Modulation), width of pulses vary with modulating signal.
Modem performs the functions of both the modulator and the demodulator. Modem acts as a modulator in the transmitting mode and it acts as a demodulator in the receiving mode.
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