Radio Receivers

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: A

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In a superheterodyne receiver with an IF of 450 kHz is tuned to a signal at 1200 kHz. The image frequency is

A:

750 kHz

B:

990 kHz

C:

1650 kHz

D:

2100 kHz

Answer: D

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The selectivity of most receivers is determined largely by

A:

sensitivity

B:

characteristics of IF section

C:

antenna direction

D:

all of the above

Answer: B

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In a superheterodyne receiver, the IF is 455 kHz. If it is tuned to 1200 kHz, the image frequency will be

A:

1655 kHz

B:

2110 kHz

C:

745 kHz

D:

910 kHz

Answer: B

A signal (image) can interfere with a superheterodyne receiver if fits the following equation.

Image = Signal +/- 2 x I.F.

Which says that a signal has the capacity to interfere with a superhet receiver if its frequency is equal to the signal frequency (1200 kHz in our question) plus or minus twice the IF (455 kHz in our question).

So one possible image is: 1200 + ( 2 x 455 ) = 2110 kHz (possible).

And the other: 1200 - ( 2 x 455 ) = 290 kHz (not likely).

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In a radio receiver, if the intermediate frequency is too high

A:

Selectivity will be poor

B:

Tracking difficulties will be least

C:

Adjacent channel rejection will improve

D:

All of the above will occur

Answer: A

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Questions for: Radio Receivers