Case Study 5
Using the antenna and LNC cost data in sections 2 and 5 specify the least cost dish size/LNC noise figure combination needed to achieve a clear sky G/T of 24 dBK. (Perform the calculations for a Ku band system).
Solution 5
In this case the G/T equation can be rewritten as
If we consider an extract from the tabulation of antenna performance we see several potential dishes.
Dish type size gain cost Tsys no (dBi) ($A retail) requirement (deg K) D1100 90 x 101 cm 40 140 40 D1200 120 x 132 cm 42.5 245 71 D1300 1.6 m 44 320 100 D1400 1.8 m 45 490 126 D1490 2.3 m 46.5 750 178
Now if we assume:
Similar calculations lead to :
Dish size gain cost TLNC LNC Noise Suggested Cost type (dBi) ($A requirement Figure LNC type ($A no retail) (deg K) Requirement number retail) (dB) D1100 90 x 101 40 140 - - n/a n/a cm D1200 120 x 42.5 245 14 0.2 n/a n/a 132 cm D1300 1.6 m 44 320 42 0.59 n/a n/a D1400 1.8 m 45 490 68 0.91 L1100 200 D1490 2.3 m 47.5 750 118 1.48 L1100 200
Least cost solution is D1400 dish with L1100 LNC.
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