Electronics and Communication Engineering - Radio Receivers - Discussion

Discussion :: Radio Receivers - Section 1 (Q.No.29)

29. 

In a broadcast superheterodynes receiver having no RF amplifier, the loaded Q of the antenna coupling circuit is 100. If the intermediate frequency is 455 kHz. The rejection ratio at 25 MHz will be

[A]. 1.116
[B]. 1.386
[C]. 2.116
[D]. 2.386

Answer: Option A

Explanation:

No answer description available for this question.

Manu said: (Nov 6, 2015)  
Explain please!

Moon said: (Jul 29, 2016)  
Please explain how.

Jam said: (Dec 8, 2016)  
Kindly explain it.

Venkat said: (Dec 28, 2016)  
Please explain it.

Ram Charan said: (Jan 3, 2017)  
F (i.f.) =455khz,
f = 25Mhz, Q = 10 here
f(s.i) means imaginary frequence.

Rejection ratio = sqrt (1+Q^2P^2).
Here P = (f(s.i)/f - f(s)/f(s.i)).
F(s.i) = f + 2f(i.f).
= 25000+2 * 455.
F(s.i) = 25910.

P= {(25910/25000) - (25000/25910)}.
= .0716.

Rejection ratio = sqrt(1+Q^2P^2).

Total solve R.r.=1.116 approx.

Rishi Ram Sharma said: (May 4, 2017)  
No,

If Q=100 than Rejection Ratio at 25 MHZ should be near 7.22.
Because of R. R = Sqrt(1+Q^2*P^2).
Where P is same as Ram Charan Calculated.

If Q=10 than Rejection Ratio at 25 MHZ should be near 1.226.
Because of R. R=Sqrt(1+Q^2*P^2).
Where P is same as Ram Charan Calculated.

Jay said: (Aug 11, 2018)  
Yes, I agree with you @Rishi Ram.

Ebenezer said: (Sep 20, 2018)  
It should be 7.22.

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