Pre-Emphasis & De-Emphasis Networks

-

Aim:- 

To draw the frequency response of Pre-emphasis & De-emphasis networks.

Introduction:-

Educational trainer a useful kit for the demonstration of Pre-emphasis & De-emphasis at different time constants & plot the graph of the frequency response of Pre-emphasis and De-emphasis networks. The kit consists of 200 Hz-20 kHz audio oscillator 70µ sec & 50µ sec De-emphasis networks.

 Pre-Emphasis Circuit Diagram:-



DE-Emphasis Circuit Diagram:-



Theory:-

Pre-emphasis refers to boosting the relative amplitudes of the modulating voltage for higher audio frequencies from 2 to approximately 15 kHz .De-emphasis means attenuating those frequencies by the amount by which they are boosted. However, Pre-emphasis is done at the transmitter and De-emphasis is done in the receiver. The purpose is to improve the signal-to-noise ratio for FM reception. A time constant of 75µ sec is specified in the RC or L/Z network for Pre-emphasis and De-emphasis.

Tabular column:-

Pre-Emphasis and De-Emphasis (Tabular column is the same for both)

Sl. Number

Frequency in Hz

i/p voltage Vin

volts

o/p voltage Vo in volts

Gain=Vo/Vin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 








Procedure:-

1) Check the apparatus properly.

2) Connections are made as shown from the circuit diagram for Pe-emphasis.

3) Switch on the power supply.

4) Set the i/p voltage for frequency 1 kHz & o/p for 4 volts.

5) Take the i/p & o/p voltage simultaneously for varying audio range frequency i.e. (20 Hz- 20 kHz).

6) First, take for the Pre-emphasis.

7)  Then calculate again & plot a grad of frequency vs. gain of a pre-emphasis.

8) For De-emphasis repeat the steps up to 5 using de-emphasis trainer kit.

9) Then calculate the gain.

10) Plot the graph of frequency vs. gain.

Pre- Emphasis Nature of graph:-

De-Emphasis nature of  Graph:-


Result: -  

We have studied the Pre-emphasis & De-emphasis circuit & plotted the frequency response of Pre-emphasis & De-emphasis network.


 


 

Comments

Post a Comment

Its not necessary everyone should know everything feel free to ask or tell :)

Popular posts from this blog

Estimation of total chlorophyll by Aron's method

-
Purpose:- Estimation of total chlorophyll by Arnon's method. Requirement:- Spectrophotometer Buchner's funnel, filter paper test tube, Fresh leaves. measuring cylinder pestle & mortar 80% Acetone  Formula:- 20.2 (A645) +802 A663) / 1000 x W Principle:- Chlorophyll is extracted in 80% acetone & the absorption at 660 nm& 645 nm are read in s spectrophotometer using the absorption co-efficient, the amount of chlorophyll is calculated Procedure:- 1) Weigh 1 gm of finely cut & well mixed representative sample of a leaf or fruit tissue into a clean mortar 2) Grind the tissue to a fine pulp with the addition of 20mil of 80% acetone   3) Centrifuge (5000 rpm for 5 min) & transfer the supernatant to a 100 ml volumetric flask  4) Repeat this procedure until the residue is colorless wash the mortar and pestle  thoroughly with 80% acetone and collect the clear washing in the volumetric flask 5) Make up the volume to 100 ml with 80% acetone  6) ...
Read more

Determination of Stefan's constant

-
Image
Aim:-  To determine the value of Stefan's constant. Apparatus:-  Black body radiation unit, Ammeter, Voltmeter, connecting wires, DC source. Theory:-  Stefan's constant: A physical constant denoted by  σ , is the constant of proportionality in the Stefan's-Boltzmann law- the total intensity radiated over all wavelength increases as the temperature increases Procedure:- 1) The electrical connections are made as shown in the circuit diagram. 2) Copper black body radiator is preheated to  30 0 C   by setting maximum voltage in the power supply 3)after the temperature indicator indicates a temperature of about    30 0 C , the voltage is reduced to some value  4) increase the voltage in steps of 0.2 V and note down the current, hence calculate power l. 5) Determine the value of Stefan's constan t. Observations:-  Room temperature t o =t+273=......of 2) surface area of the black body  A=4π r 2  = .........m square Calculati...
Read more