With an IF of 455 kHz, what is the local oscillator frequency when a radio receiver is tuned to 855 kHz_______________?
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Answer: B. 1310 kHz
Explanation
The local oscillator frequency in a superheterodyne receiver is typically tuned above the incoming signal by the intermediate frequency. Adding the incoming signal frequency of 855 kHz to the intermediate frequency of 455 kHz gives the local oscillator frequency. The resulting calculation of 855 kHz plus 455 kHz yields a local oscillator frequency of 1310 kHz. Superheterodyne receivers use the heterodyning principle where the local oscillator tracks above the radio frequency. The intermediate frequency remains constant at 455 kHz for standard AM broadcast band radio receivers. Gang capacitors simultaneously tune both the RF input circuit and the local oscillator to maintain this frequency difference.
455 kHz represents only the intermediate frequency value rather than the local oscillator operating frequency. 1500 kHz and 1520 kHz are incorrect calculation results that do not match the specified signal and IF sum. None of the other numerical options correctly sum the incoming radio frequency and intermediate frequency values.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
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