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Write a short note on Double spotting
written 5.5 years ago by | • modified 5.5 years ago |
Subject: Principles of Communication Engineering
Difficulty : Medium
Marks : 05
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written 5.5 years ago by | • modified 5.5 years ago |
Subject: Principles of Communication Engineering
Difficulty : Medium
Marks : 05
written 5.5 years ago by |
Double spotting
Consider an incoming strong signal of 1000 kHz and local oscillator tuned at 1455 kHz. Thus a signal of 455 kHz is produced at the output of the mixer which is the IF frequency.
Now consider the same signal but with 545kHz tuned local oscillator. Again we get 455 kHz signal at the output.
Therefore the same 1000 kHz signal will appear at 1455 kHz as well as 545 kHz on the receiver dial and the image will not get rejected. This is known as Double spotting phenomenon.
It is also known as Adjacent channel selectivity.