# Electronics and Communication Engineering - Satellite Communication - Discussion

Discussion Forum : 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.
100
4
1
10
Explanation:
No answer description is available. Let's discuss.
Discussion:
12 comments Page 1 of 2.

Anurag Nande said:   9 years ago
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.
(1)

Nirav Solanki said:   10 years ago
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.

Zarana said:   9 years ago
How put 5?

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

(1)

Shreya said:   9 years ago
20m antenna-----4/6GHZ-----multiply by 5.

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

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

Shivanirajput said:   9 years ago
Antenna diameter is inversely proportional to frequency. So f*5 = d/5 = 4m.

Lambda = c/f.
If f' = 5f.
Then lambda' = lemda/5 = height of antenna = 4m.

Antenna diameter is inversely proportional to the operating frequency.

Amul said:   8 years ago
Thanks for the explanation. It's very easy to understand.

Suresh said:   9 years ago
Thanks to explaining all of these.

THANAM SIVA said:   7 years ago
Thanks for explaining it.
(2)