The presentation focuses on the components/concepts that build up any basic radio receiver. The presentation focuses on the concepts and characteristics of Receiving Antenna, LC or oscillatory circuits, rectifiers and Audio Amplifiers.

1. Radio Receiver
Group-1 ADC, SEM-IV
Kavi Pandya - 131020
Maninder Sambhi - 131024
Prarthana Padia - 131035
Prem Shah - 131036

2. Antenna and Ground
Antenna
● made of copper wire(open or isolated)
● length - 6m or more
● follows TLTB Law (the Longer, the Better)
● not to be placed near electronic devices
● act as voltage generator because of resistance & capacitance(C1)
● C1 ∝ length of antenna
Ground
● used for better reception
● receiver ground connected to ground via copper wire
● copper wire connected to plumbing pipe of length 80cm
● connection made with ring and a screw with bolt

3. Oscillatory Circuit
(This parallel LC Circuit acts as oscillator circuit as charging of capacitor reduces magnetic field of inductor
and vice-versa which results in an infinite sinusoids. It consists of variable capacitor and fixed inductor.)
It has two functions to perform in Radio Receiver :
i)Band-Pass Filter/Separate the signal of required Station from Others – Antenna receives various signals both
required and unrequired. To separate out the required signal we tune the capacitor to the same
frequency(resonant) as that of the required signal.●
ii)Amplify the signal and proceed to rectifier – The gain of Band-Pass filter is multiplied with the tuned signal thus
amplifying the input signal.
Input of Oscillator Circuit :
α(V1 + m1(t))Cos(w1t) + α(V2 + m2(t))Cos(w2t) + ….. + α(Vi + mi(t))Cos(wit)
Output of Oscillator Circuit :
If we need the signal with frequency at w4, so we tune the capacitor accordingly and get:
kα(V4 + m4(t))Cos(w4t)
α – attenuation and k – band-pass gain. Thus Oscillator acts as band-pass filter(allowing only signal at frequency
w4 to pass) and amplifier(as the output signal is multiplied by the gain of band-pass filter)

4. Rectifier
AM Signal Detector:
The rectifier performs the function of eliminating and obtaining the original signal from the amplified
one received from the transmitter
The AM signal detector (rectifier) comprises of a diode capacitor and the headphone resistance. The
output obtained is an envelope of the AM signal containing only original signal: Gain*(mit)cos(wit)
Here, the product of the capacitance and the headphone resistance should be approximately equal to
50 microseconds
The headphones are used here to convert the electrical signal into sound that can be heard. The
original signal obtained after passing through the rectifier can be heard through the headphones which
are of 3 kU resistance.
Here the original output is obtained when the AM signal of the station to which the receiver is tuned is
brought on its input.

5. LF Audio Amplifier
Need: To enhance the sound reproduction on the receiver’s end.
Components significance:
C4: Used because it obtains the voltage negative feedback
R2: Adjusts the transistor optimal reproduction
R3: Used because it obtains the current negative feedback
C5: Prevents the AM signal carrier
Use of R3, C4 increases Stability, reduces Distortion and widens the reception band. But for this, the
trade-off is reduction in amplification.
This Audio (LF) amplifier adjusts the gain.
Let output voltage= Vo,
Vo=KifKKmKbαVm(t)
If α increases, Kb needs to be reduced. This could be managed by the Audio amplifier.

6. Reference
1.http://www.mikroe.com/old/books/rrbook/rr
book.htm