Question: Q. 1. What is sky wave propagation ? Which frequency range is suitable for sky wave propagation and why ? Over which range of frequencies can communication through free space using radio waves take place?
U] [2017, Foreign Set-1I]
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Solution:
Ans. In sky wave propagation, long distance communication is achieved by ionospheric reflection of radio waves back towards the earth. 1 The frequency range is from afew-Mega hertz to 30/40 Mega hertz. The ionospheric layers can act as a reflector over thiş frequency range $(3 \mathrm{MHz}$ to $30 / 40 \mathrm{MHz}$ ). Higher frequencies penetrate through it.
The frequency range of radio frequencies is a few hundred $\mathrm{kHz}$ to a few $\mathrm{GHz}$.
(waves having frequency beyond $40 \mathrm{MHz}$ ) 1
[CBSE Marking Scheme, 2017]
Commonly Made Error
- Many students confused ‘sky wave propogation’ with’ space wave propagation.’
