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Question
The maximum frequency for reflection of sky waves from a certain layer of the ionosphere is found to be fmax = 9(Nmax)1/2, where Nmax is the maximum electron density at that layer of the ionosphere. On a certain day, it is observed that signals of frequencies higher than 5 MHz are not received by reflection from the F1 layer of the ionosphere while signals of frequencies higher than 8 MHz are not received by reflection from the F2 layer of the ionosphere. Estimate the maximum electron densities of the F1 and F2 layers on that day.
Solution
`d_m^2 = 2(R + h_T)^2`
`8Rh_T = 2(R + h_T)^2` ......(∵ `dm = 2sqrt(2Rh_T))`
`4Rh_T = R^2 + h_T^2 + 2Rh_T`
`(R - h_T)^2` = 0
`R = h_T`
Since space wave frequency is used, λ << hT, hence only tower height is taken into consideration. In three dimensions, 6 antenna towers of hT = R would do.
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