written 7.7 years ago by | • modified 2.7 years ago |
Mumbai University > Electronics Engineering > Sem 5 > Electromagnetic Engineering
Marks: 5 Marks
Year: Dec 2014
written 7.7 years ago by | • modified 2.7 years ago |
Mumbai University > Electronics Engineering > Sem 5 > Electromagnetic Engineering
Marks: 5 Marks
Year: Dec 2014
written 7.7 years ago by |
a) Critical frequency:
It is that highest frequency radio wave, which sent normally towards layer of ionosphere gets reflected back & returns to the earth.
$f α \sqrt{N} \\ f= g \sqrt{N} \\ f= g(N_{\max} )^{\frac{1}{2}}$
where, N → free electron density
b) Maximum usable frequency (MUF):
It is that highest frequency of radio waves which when sent at some angle towards ionosphere, gets reflected and returns to the surface of the earth.
$MUF=\dfrac{f_c}{\cos i} \\ MUF=f_c.\sec(i) \\ Also, MUF=f_c \sqrt{1-\dfrac{D^2}{4h^2}}$
Where , $\text{D → skip distance} \\ \text{i → Angle between normal and direction of incident wave.}$
c) Optimum working frequency (OWF):
The frequency normally used for ionosphere transmission is known as optimum working frequency. Usually, it is taken as 15% of MVF.