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Submitted By,

Group-5Devanshi Piprottar (131011)Rajvi Trivedi (131039)Shailaja Sampat (131046)Preksha Chavda (121036)

OVERVIEW OF RADIO RECEIVER SYSTEM…

Radio Receiver

Antenna

V

f A

Electric Field

AM station

FUNCTIONS OF RADIO RECEIVER AT A GLANCE…

Separation of signal of required frequency i.e. tuned in the radio

Minimizing effect of all other signals present around (dependent on power of the signal and geographic distance)

Amplification of the extrapolated* signals, obtaining information from them and reproduction of that information into original form

* Extrapolation: When incoming signal is sampled periodically, using the current data values for approximation of the next data point values is called extrapolation.

COMPONENTS OF DETECTOR RADIO RECEIVER: Oscillatory Input Circuit (Inductor + Capacitors (variable & coupling)):

Uses: 1. Signal Separation

2. Voltage Amplification

Characteristics of Oscillatory Circuit:

- Resonance Frequency 1/C*, 1/F

- Impedance(Z) f

Extras:

- Voltage between two ends of oscillator (V)= Current (A)* Impedance ( )

- Resonance frequency is set to be equal to the carrier frequency of AM wave

* Resonant Frequency value varies in inverse proportion as variable capacitance changes its value

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COMPONENTS OF DETECTOR RADIO RECEIVER:

Lower boundary Upper boundary

carrier frequencies of different radio transmitters

Currently tuned frequency

COMPONENTS OF DETECTOR RADIO RECEIVER:

Serial Diode Detector (Diode + Capacitor + Resistance of headphones):

Uses: 1. Extraction of Information

Extras: - Diode should be of low-power germanium type

Output device (Headphones):

Uses: 1. Information Restoring

Extras: - Receiver will work better as resistance in parallel to headphone is bigger

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C

COMPONENTS OF DETECTOR RADIO RECEIVER:

Antenna:

Extra:

- Antenna is made of copper wire (more convenient is Litz wire*) which is thick enough to get protection against weather conditions

- The Longer is antenna, Better its functionality (> 6m)- Antenna is the best HF (High Frequency) amplifier

CAUTION: Put antenna such that it remains isolated from network cables / walls / metal parts in surrounding

*Litz wire: which has huge number of thin threaded copper wires

COMPONENTS OF DETECTOR RADIO RECEIVER: Inductor (Coil):

Extras: -

- Coil is generally made up of cylindrically shaped isolation material (here aluminium with diameter 0.3mm) and #turns also matters (provided the length of wire)

- Lesser the diameter, more #turns

- Parasite capacitance = Trimmer capacitor* + Variable capacitor in parallel

- Cx is assumed to be some specific value (here Cx=15pF) and L is calculated

* Trimmer Capacitor: The electronic parts whose capacitance can be changed freely. Trimmer capacitors are variable capacitors they need not be adjusted continuously which is used in tuning of radio.

COMPONENTS OF DETECTOR RADIO RECEIVER: Ground:

Extras:

- Connecting receiver to the ground (for better reception)

- Water plumbing, Electrical ground, Soil beneath are possible ground methods

Others:

Extras:

- Hubs with isolated plates

- Coupled capacitor which is responsible for transferring signals from antenna to oscillatory circuit and its value depends on length of antenna

COMPONENTS OF DETECTOR RADIO RECEIVER:

Variable Capacitor:

Extras:

- 2 variable capacitance + 2 trimmer capacitor

(with minimal capacitance) in parallel

(4 + 4 capacitors in parallel in commercial radios)

WORKING METHODOLOGY:

Reception antenna behaves as a voltage generator, having internal resistance and capacitance. Resistance damps the oscillatory circuit and reduces its selectivity (prevents mixing of stations) and sensitivity (signal strength reduction). Antenna's Capacitance reduces the reception bandwidth. These both factors are undesirable. Capacitance at which signals from antenna will not be much weakened while simultaneously considering appropriate selectivity and bandwidth. Hence choose largest Capacitance value (>30pF) at which all the stations of interest are included and the strongest of them does not jam the reception of other stations. Output of Reception antenna is provided to oscillatory circuit. Then inductance value is calculated as described previously.

ADVANTAGES OF RADIO RECEIVER… Simplicity Very less power consumption (from antenna itself) No need of external power sources Good ground facility added to it provides better distant transmission

Normal reception won’t be possible due to geographic distance dependency of transmitter

Cover only signals of the local and powerful radio transmitters Antenna has to be long enough and voltages induced should also be high enough Amplifier should be strong enough to give the end result better and nullify the

effect of noise

LIMITATIONS OF RADIO RECEIVER…

THE SIMPLEST AMPLIFIED RADIO RECEIVER

To overcome the limitation of previous radio receiver that is it can perform sound reproduction loud enough only in case of signals from very powerful radio transmitter is being received, this receiver with Low Frequency amplifier (NPN) is invented. It also helps to achieve limitation of length of antenna.

THE SIMPLEST AMPLIFIED RADIO RECEIVER:

Differences w.r.t Simplest Radio Receiver:- The electrical load in the detection stage is resistor R1 instead of headphones- Voltage negative feedback using capacitor C4 - Current negative feedback using resistor R3

Printed circuit can be achieved using vitroplast plate*

*Vitroplast: vitro means derived from vitrinite (a type of natural source) and plast is derived from plasty.

Thank You…

Reference: http://www.mikroe.com/old/books/rrbook/chapter3/chapter3a.htm#3.1. The Simplest Radio Receiver