In a typical AM receiver circuit, the oscillator frequency is

This question was previously asked in
ESE Electrical 2014 Paper 2: Official Paper
View all UPSC IES Papers >
  1. Same as the signal frequency
  2. Always equal to 455 Hz
  3. Lower than the signal frequency by 455 kHz
  4. Higher than the signal frequency by 455 kHz

Answer (Detailed Solution Below)

Option 4 : Higher than the signal frequency by 455 kHz
Free
ST 1: UPSC ESE (IES) Civil - Building Materials
6.5 K Users
20 Questions 40 Marks 24 Mins

Detailed Solution

Download Solution PDF

The most typical AM receiver circuit is the superheterodyne (SHD) receiver.

In the receiver circuit, the local oscillator frequency is:

fLO = fRF + fIF

Where,

fRF = radio-frequency or signal frequency.

fIF = Intermediate frequency.

Since, for AM broadcast, the typical intermediate frequency is 455 kHz.

So, fLO = fRF + 455

This is showing that fLO must be higher than the signal frequency by 455 kHz.

26 June 1

Important Parameters for AM and FM signals are:

Parameters

AM

FM

Carrier frequency

540 – 1700 kHz

88.1 – 107.9 MHZ

Carrier spacing

10 KHZ

200 kHz

Intermediate frequency

455 kHz

10.7 kHz

IF Bandwidth

6 – 10 kHz

200 – 250 kHz

Audio Bandwidth

3 – 5 kHz

15 KHZ

Latest UPSC IES Updates

Last updated on Jul 2, 2025

-> ESE Mains 2025 exam date has been released. As per the schedule, UPSC IES Mains exam 2025 will be conducted on August 10. 

-> UPSC ESE result 2025 has been released. Candidates can download the ESE prelims result PDF from here.

->  UPSC ESE admit card 2025 for the prelims exam has been released. 

-> The UPSC IES Prelims 2025 will be held on 8th June 2025.

-> The selection process includes a Prelims and a Mains Examination, followed by a Personality Test/Interview.

-> Candidates should attempt the UPSC IES mock tests to increase their efficiency. The UPSC IES previous year papers can be downloaded here.

Get Free Access Now
Hot Links: online teen patti yono teen patti teen patti game online