Organize and Share your Electronics the way you want. Sign-Up for a free account now. It takes only 30 seconds!

How a radio receiver work

How a radio receiver work

On this page the author will explain for you how a radio receiver works. Almost every receiver works in the same way. One of the circuit he used in his projects is the MC13135/MC13136. It is the second generation of single chip, dual conversion FM communication receivers developed by Motorola. Major improvment in signal handling, RSSI and first oscillator operation have been made.
At pin 22 you will find the RF-input this is the antenna input connection. This receiver will receive at 49.7 MHz. The RF signal will mix with the crystal oscillator (39MHz) pin 1 and 2. The product frequency 49.7-39 =10.7MHz will come out at pin 20. A ceramic filter removes all other frequences except the 10.7MHz wich will enter at pin 18. Here you will find a new mixer wich will mix the 10.7MHz with another crystall oscillator (10.245MHz) pin 5 and 6. The product frequence 10.7-10.245 =455kHz will come out at pin 7. A ceramic filter removes all other frequences except the 455kHz wich will enter pin 9.

Now, you have tiny signal at 455kHz wich will vary a little around 455kHz depending on the FM-modulation (+/- some kiloherts). This tiny signal must be amplified to a level where the audiosignal can be demodulated from the RF-signal. The tiny RF-signal will also vary in strength depending how close you are to the transmitter. What you want is a constant level wich is not depending on the distance to the transmitter.

So, there is a amplifying-limiting stage at pin 9,10,11, and 12. This stage amplify the tiny RF-singal to a constant safe level where the demodulator can demodulate the audio-signal. This stage could be called a voltage controlled gain-stage. As you might understand, the closer you are to a transmitter the strong the RF-signal will be, and in such case the limiter will not have to gain the signal so much. The amplifier has a very wide amplifying area, from 100 to some milion times. The voltage to control the gain is called (Received Signal Strength Indicator) RSSI and can be found at pin 12 and 15. Here you will find a voltage from 0.4 – 1.2 volt

Visit Here for more.







 

More Articles to Read

Peeqo is a desktop bot that communicates through GIFs
Peeqo is a desktop bot that communicates through GIFs
Using a Programmable Input Multiplier to Minimize Integer Boundary Spurs
Using a Programmable Input Multiplier to Minimize Integer Boundary Spurs
Serial seven segment LED display shield
Serial seven segment LED display shield
G-code controlled drawing plotter
G-code controlled drawing plotter
An Arduino round word clock
An Arduino round word clock
The Sandwich-o-Matic will make your lunch automatically
The Sandwich-o-Matic will make your lunch automatically
Scalar Network Analyser Jr
Scalar Network Analyser Jr
An Arduino-controlled automated whiskey distillery
An Arduino-controlled automated whiskey distillery
The Rex800 looks like a dinosaur Terminator
The Rex800 looks like a dinosaur Terminator
Home Environment Monitor
Home Environment Monitor
Understanding the Operation of the Frequency Synthesizer in Maxim’s RF Transceivers
Understanding the Operation of the Frequency Synthesizer in Maxim’s RF Transceivers
App note: EPIC: Electro-Pyrotechnic Initiator Chip Resistor
App note: EPIC: Electro-Pyrotechnic Initiator Chip Resistor
Noisy ESP8266
Noisy ESP8266
App note: Noise analysis for high-speed op amps
App note: Noise analysis for high-speed op amps
Skill Sunday: Arrays
Skill Sunday: Arrays
App note: Infrared remote control implementation with MSP430FR4xx
App note: Infrared remote control implementation with MSP430FR4xx
Gesture Controlled Smart Home
Gesture Controlled Smart Home
Design for a Wideband, Differential Transimpedance DAC Output
Design for a Wideband, Differential Transimpedance DAC Output
Wrist thrusters let you fly through the water effortlessly
Wrist thrusters let you fly through the water effortlessly
Bertan/Spellman 225-20R HV power supply teardown
Bertan/Spellman 225-20R HV power supply teardown

Top


Shares