Electronics and Communication Engineering - Satellite Communication - Discussion

Discussion :: Satellite Communication - Section 1 (Q.No.5)

5. 

A 20 m antenna gives a certain uplink gain at frequencies of 4/6 GHz. For getting same gain in the 20/30 GHz band, antenna size required is metre.

[A]. 100
[B]. 4
[C]. 1
[D]. 10

Answer: Option B

Explanation:

No answer description available for this question.

Prakhar said: (Apr 1, 2014)  
Antenna diameter is inversely proportional to the operating frequency.

Nisha said: (May 29, 2014)  
Lambda = c/f.
If f' = 5f.
Then lambda' = lemda/5 = height of antenna = 4m.

Nirav Solanki said: (Jan 19, 2015)  
Here frequency is multiplied by 5 means the wavelength is divided by 5.

Now length of antenna is directly proportional to the half of the wavelength. So the ultimate length of antenna is divided by 5.

Shreya said: (Feb 24, 2015)  
20m antenna-----4/6GHZ-----multiply by 5.

?---------------20/30GHZ.

4*5/6*5-----20/5=4m.

Anurag Nande said: (Apr 6, 2015)  
Antenna diameter (d) is inversely proportional to the operating frequency (f).

So d = k*(1/f).

Note :- Here k is constant.

For up link f = 4GHz for down link f = 6GHz.

d = k*1/4 d = k*1/6.

d/5 = k*1/(4*5).

d/5 = k*1/(6*5).

d/5 = k/20 ---(1)

d/5 = k/30----(2).

So the resultant size of antenna from equation (1) and (2):

Size = d/5 = 20/5 = 4m.

Size = 4m.

Shivanirajput said: (Jun 18, 2015)  
Antenna diameter is inversely proportional to frequency. So f*5 = d/5 = 4m.

Zarana said: (Sep 17, 2015)  
How put 5?

We need height of 20/30 frequency. So do 4*5/6*5 & dived by 5 to 20 meter height?

So answer is 4?

Suresh said: (Nov 26, 2015)  
Thanks to explaining all of these.

Indu said: (Mar 17, 2016)  
How put 5?

Amul said: (Aug 13, 2016)  
Thanks for the explanation. It's very easy to understand.

Thanam Siva said: (Jan 2, 2018)  
Thanks for explaining it.

Vaishu said: (Jan 23, 2020)  
How 5?

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