Question

Give three reasons why modulation of a message signal is necessary for long distance transmission ?

Answer 1

heya!!!

i) To separate signal from different transmitters :-

Audio frequencies are within the range of 20 Hz to 20 kHz. Without modulation all signals at same frequencies from different transmitters would be mixed up. There by giving impossible situation to tune to any one of them. In order to separate the various signals, radio stations must broadcast at different frequencies.

Each radio station must be given its own frequency band. This is achieved by frequency translation as a result of modulation process.

ii) Size of the antenna : –

For efficient transmission the transmitting antennas should have length at least equal to a quarter of the wavelength of the signal to be transmitted. For an electromagnetic wave of frequency 15 kHz, the wavelength λ is 20 km and one-quarter of this will be equal to 5 km. Obviously, a vertical antenna of this size is impractible. On the other hand, for a frequency of 1 MHz, this height is reduced to 75 m.

Also, the power radiated by an antenna of length l is proportional to (l/λ). This shows that for the same antenna length, power radiated is large for shorter wavelength. Thus, our signal which is of low frequency must be translated to the high frequency spectrum of the electromagnetic wave. This is achieved by the process of modulation.

iii)To Reduce  Antenna Height.
(practicability of antennas height).

iv)Transmit The Information To long Distance Without  interference.

v) Reduce band width.

hope it may help you :-)

plzz mark brainleist