Unlike A.M.radio transmitters, TV transmitters can cover a distance of 60km to 65km only. You might have noted that this limitation in the range of a TV transmitter is due to the fact that the carrier used for TV transmission is in the V.H.F and U.H.F. range. They are not reflected by the ionosphere and the curvature of the earth places the above mentioned limit in the range of terrestrial TV transmitters.
You might be remembering the expression for the range ‘d’ of a TV transmitter:
d = √(2Rh) where R is the radius of the earth and h is the height of the TV transmitter tower.
The above expression is the approximation of the expression, d = √(2Rh+h^2), obtained by ignoring h^2 which is small compared to 2Rh.
Now consider the following M.C.Q.:
To cover a population of 3 million, what should be the height of a TV transmitter tower? (Population per square km = 1000)
(a) 25m (b) 45m (c) 55m (d) 65m (e) 75m
If ‘d’ is the required range of the TV transmitter, the coverage area = πd^2 = π×2Rh so that we have, 1000 π×2Rh = 3×10^6.
The radius of the earth is 6400km which you are expected to remember. You may substitute for R in km itself in the above equation to obtain h to be approximately 0.075km = 75m. The correct option therefore is (e).
You might be remembering the expression for the range ‘d’ of a TV transmitter:
d = √(2Rh) where R is the radius of the earth and h is the height of the TV transmitter tower.
The above expression is the approximation of the expression, d = √(2Rh+h^2), obtained by ignoring h^2 which is small compared to 2Rh.
Now consider the following M.C.Q.:
To cover a population of 3 million, what should be the height of a TV transmitter tower? (Population per square km = 1000)
(a) 25m (b) 45m (c) 55m (d) 65m (e) 75m
If ‘d’ is the required range of the TV transmitter, the coverage area = πd^2 = π×2Rh so that we have, 1000 π×2Rh = 3×10^6.
The radius of the earth is 6400km which you are expected to remember. You may substitute for R in km itself in the above equation to obtain h to be approximately 0.075km = 75m. The correct option therefore is (e).
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