---
title: "AM superheterodyne radio receiver diagram"
subject: "Basic Electronics Engineering"
chapter: 5
key: "semester_2/basic_electronics_engineering:am-superheterodyne-receiver"
source: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/am-superheterodyne-receiver
site: BCT Engineering
---

# AM superheterodyne radio receiver diagram

Basic Electronics Engineering · Chapter 5: Communication System

- Asked in: 2067 Chaitra, 2 marks
- Video: [Superhetrodyne Receiver - Modern Electronic Communications - Application of Electronics](https://www.youtube.com/watch?v=rJ1MWlh9_ao) — Ekeeda
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/am-superheterodyne-receiver
- Whole chapter: https://www.bctengineer.com/md/semester_2/basic_electronics_engineering/chapter-5

## Question

Draw a block diagram of AM super heterodyne radio receiver.

## Short answer

The AM superheterodyne receiver converts the incoming RF signal to a fixed 455 kHz IF using a mixer and local oscillator. It consists of RF amplifier, mixer, local oscillator, IF amplifier, detector, AGC, audio amplifier, and speaker.

## Answer

In a superheterodyne receiver, the incoming RF signal is converted to a fixed intermediate frequency (IF, 455 kHz for AM) before amplification and detection.

```text
 Ant -> [RF amp] --> [Mixer] --> [IF amp] --+
                        ^                   |
                        |                   v
               [Local oscillator]      [Detector] --> AGC (to RF and IF amps)
               (fLO = fRF + 455 kHz)        |
                                            v
                                        [AF amp]
                                            |
                                            v
                                        [Speaker]
```

- **RF amplifier:** selects and amplifies the wanted station and rejects the image frequency.
- **Mixer + local oscillator:** produce fIF = fLO − fRF (a constant 455 kHz).
- **IF amplifier:** gives most of the gain and selectivity.
- **Detector:** recovers the audio from the AM envelope; it also gives the AGC voltage that controls the gain of the RF and IF stages.
- **Audio amplifier and speaker:** amplify the audio and reproduce the sound.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the IF for AM and why fixed?
   A. 10.7 MHz; for AM
   B. 455 kHz; to give constant gain and selectivity
   C. 455 MHz; for FM
   D. It varies with station
   Answer: B. Converting every station to the same IF simplifies the IF amplifier. (Key point: Fixed IF)

2. How is the IF produced?
   A. fIF = fLO + fm
   B. fIF = fRF × fLO
   C. fIF = fRF − 455 kHz
   D. fIF = fLO − fRF
   Answer: D. The local oscillator runs at fRF + 455 kHz. (Key point: Mixer output)

3. What does the IF amplifier provide?
   A. Audio recovery
   B. Most of the gain and selectivity
   C. Station tuning only
   D. Loudspeaker driving
   Answer: B. Detector recovers audio; IF amp gives gain. (Key point: IF amplifier)

4. What does AGC do?
   A. Generates the local oscillator
   B. Rejects audio
   C. Converts IF to RF
   D. Controls gain of RF/IF stages using detector voltage
   Answer: D. AGC keeps output level steady. (Key point: AGC)

## Related in Basic Electronics Engineering

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## Related in other subjects

- [Superheterodyne AM receiver; why standard AM in broadcasting](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Asuperhet-am-receiver-standard-am) — Communication Systems, chapter 2, asked 2×
- [FM superheterodyne radio receiver](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Afm-superheterodyne-receiver) — Communication Systems, chapter 3, asked 2×
- [Requirements of a good radio receiver; superheterodyne](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Agood-receiver-superheterodyne) — Communication Systems, chapter 2
- [AM vs FM superheterodyne receiver; AGC](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aam-fm-superhet-agc) — Communication Systems, chapter 3