# Electronics and Communication Engineering - Microwave Communication - Discussion

### Discussion :: Microwave Communication - Section 1 (Q.No.22)

22.

The width of a radio beam from a 1 m diameter parabolic antenna at 10 GHz is about

 [A]. 100° [B]. 50° [C]. 5° [D]. 1°

Explanation:

.

 Jagriti said: (Dec 23, 2014) What is 140?

 Lavanya said: (Jan 16, 2015) 140 is for antenna factor.

 Goldy said: (Jul 14, 2015) Please explain in detail.

 Aravind said: (Aug 1, 2015) 140c/wavelength.

 Rose said: (Sep 30, 2015) Kc/wavelength. Where k is a factor which varies slightly depending on the shape of the reflector and the feed illumination pattern. For an ideal uniformly illuminated parabolic reflector and θ in degrees, k would be 57.3 (the number of degrees in a radian). For a "typical" parabolic antenna k is approximately 70. How 140?

 Dhruv said: (Jun 8, 2016) @All. Beam width b/w half power points in a parabolic reflector = 70 * (lambda/diameter). Therefore, beam width b/w first nulls = 2 * half power bw. Then, we get 140.

 Sankar said: (Oct 14, 2017) I think 140 (λ) /diameter then we get above equation.

 Ayush Kumar said: (Nov 3, 2017) Yes beam width = 140(lambda)/diameter.

 Sreeram said: (Feb 15, 2018) (140 (wavelength))/diameter.

 Asus said: (Jun 24, 2018) Why 140?

 Zecru said: (Dec 19, 2018) We use 70 for the Half Power Beam Width only.