Superhetrodyne Radio Receiver

INTRODUCTION:

Today in this instructables I shall teach you about a Superhetrodyne Radio Receiver.

SUPERHETRODYNE RADIO RECEIVER
Superhetrodyne radio receiver uses the principle of Superhetrodyne, so this is why this receiver is known as superhetrodyne radio receiver.

PRINCIPLE OF SUPERHETRODYNE

Principle of Superhetrodyne Radio receiver was invented by an American Electrical engineer named Sir. Edwin Howard Armstrong in 1918. All radio receivers (MW, SW, LW, FM) that we use at our home, use the principle of superhetrodyne.

According to the principle of superhetrodyne-" Rf signal received by the antenna is amplified by a tuned amplifier. This tuned amplifier is called Radio frequency Amplifier or RF Amplifier for short. After amplifying the received RF signal, Output of RF Amplifier is given to mixer. Mixer mixes the frequency of RF signal with the frequency of Local oscillator's signal and produces an output signal which has frequency of the RF signal, Local oscillator signal, Frequency of Local oscillator signal + frequency of RF signal or Frequency of Local oscillator signal - Frequency of RF signal. Thus output of mixer is four different frequency signals. These four frequencies are following-

1. f (RF) - Frequency of RF signal
2. f (LO) - Frequency of Local oscillator signal
3. f (RF) + f (LO) - sum of the frequencies of local oscillator signal and RF signal
4. f (LO) - f (RF) - difference of the frequencies of local oscillator signal and RF signal "
   

The output signal of the mixer which has frequency of the difference of local oscillator signal frequency and RF signal frequency is known as Intermediate Frequency or IF. International community of Radio has fixed this IF or intermediate frequency for different radios for Examples - intermediate frequency (IF) of Amplitude Modulation (AM) radio is 455 KHz and intermediate frequency (IF) of Frequency Modulation receiver is10.7 MHz

Local oscillator is basically an RF (Radio Frequency) LC oscillator that generates a sine wave and the frequency of this sine wave is always kept higher than frequency of received RF. The frequency of local oscillator can be easily calculated by the given formula -

• f (LO) = f (RF) + f (IF)
• f (IF) = f (LO) - f (RF)
• f (RF) = f (LO) - f (IF)

Parameters:

f (LO) = frequency of local oscillator signal.

f (RF) = frequency of received RF signal.

f (IF) = intermediate frequency of the radio receiver.

ANTENNA
Antenna is a transducer that converts the radio frequency signals into an electrical signal. A metallic conductor or wire of any metal is also an example of Antenna. Size, shape and type of antenna depends on the frequency of RF signal that is to be received by the antenna