COMMUNICATION ENGINEERING ASSIGNMENT(INSTITUTE ELECTIVE-1) SEM-4 SVMIT

DEPARTMENT OF ELECTRONICS AND
TELECOMMUNICATION ENGINEERING
SVMIT, BHARUCH

Communication Engineering
Elective-
Institute Elective-I
Subject Code: 141102

B.E. II (4th Sem.) (………………………)
(………………………

CERTIFICATE

This is to certify that Mr./Ms………………….

………………………………………………….Of B.E.…

Semester……Enrollment No …………….……………. Branch

……………………….has been found satisfactory in the continuous

internal evaluation of the laboratory, practical and term work in the subject

…………………… for the academic year 20… – 20…

Date: Sign. of teacher:

INDEX
Sr. No. Title Date Sign Marks/
Grade

EXPERIMENT 1 Date ___________

DSB-AM TRANSMITTER AND MEASUREMENT OF MODULATION
INDEX USING TRAPEZOIDAL METHOD

AIM : To study the working of Double Side Band Amplitude Modulation
(DSB-AM) Transmitter.

APPARATUS : (1) DSB AM Trainer Kit
Model No. ST 2201, Transmitter
(2) Connecting probes.
(3) Power cord.
(4) C.R.O.
(5) C.R.O. Probes.

PROCEDURE : (1) Connect the probes at the indicated points from figure in the
given trainer kit.
(2) Adjust frequencies and gain at different points and observe
the transmitted signal.
(3) Observe the waveforms at different points using C.R.O.
(4) Draw the observed waveforms.
(5) Observe the effect of change in amplitude of information
signal on modulated signal.
(6) Use trapezoidal method to measure the modulation index
(7) Connect X channel of CRO to output of audio amplifier and
Y channel of CRO to output of output amplifier.
(8) Place CRO in X-Y mode.
(9) Using Lissajous pattern find Emax and Emin.
(10) Find modulation index % ma = [(Emax-Emin)/(Emax+Emin)] x
100%.

GRAPHS : (1) Audio Signal (2) Carrier Signal
(3) BM – BPF Output (4) Output Amplifier
(5) Lissajous patterns for modulation index measurement

CONCLUSION :

CIRCUIT BLOCK DIAGRAM :

Balanced Antenna
(1) Modulator with (3)
Audio Oscillator carrier Output Amplifier (4)
Freq Amp reinsertion and Gain
BPF

(2)

Audio Amplifier 1 MHz crystal
Gain oscillator (carrier)

Speaker

Marks/Grade Teacher’s Signature


DSB-AM RECEIVER

AIM : To study the working of Double Side Band Amplitude Modulation
(DSB-AM) Receiver.

Model No. ST2201 for transmitter, ST 2202 for Receiver
(3) Power Cord.
(4) C.R.O.
(5) C.R.O. Probes.

PROCEDURE : (1) Connect the transmitter output to receiver input.
(3) At the receiver side observe the waveforms at different points
using C.R.O.
(4) Adjust gain & freq. properly at different points and try to get
the recovered audio signal same as input.

GRAPH : (1) RF Amplifier Output (2) Local Oscillator Output
(3) Mixer Output (4) IF Amplifier-2 Output
(5) Diode Detected Output (6) Audio Amplifier Output.

CONCLUSION :


Antenna

Rf If If Diode
(1) (3) Amplifier- (4) (5)
Amplifier Mixer Amplifier - Detector
Gain 1 2

(2)

Audio (6)
Tuning Local Amplifier Speaker
Oscillator Gain (variable)



DSB – AM WITH AGC CIRCUITS

AIM : To study working of Double Side Band Amplitude Modulation
(DSB-AM) with AGC (Automatic Gain Control) Circuits

(2) Model No. ST2201 for transmitter, ST 2202 for Receiver
(4) Power Cord.
(5) C.R.O.
(6) C.R.O. Probes.
(7) Digital Multimeter

PROCEDURE : (1) Connect the transmitter output to receiver input.
using C.R.O.
(4) Adjust gain & freq. properly at different points and try to get
the recovered audio signal same as input.
(5) Connect the DMM at the input of AGC circuits and note the
AGC voltage

OBSERVATION TABLE :

Output Amplifier P- P Voltage AGC Voltage (V)
Sine Wave (V)

CONCLUSION :

CIRCUIT BLOCK DIAGRAM

AGC
Circuit
Antenna

RF Amplifier IF IF Diode
Mixer
Gain Amplifier-1 Amplifier-2 Detector

Local Audio
Tuning Speaker
Oscillator Amplifier

RECEIVER



SSB-AM TRANSMITTER

AIM : To study the working of Single Side Band Amplitude Modulation
(SSB-AM) Transmitter.

APPARATUS : (1) SSB AM Trainer Kit
Model No. ST 2201, for transmitter.
(3) Power Cords
(4) C.R.O.
(5) C.R.O. Probes

PROCEDURE : (1) Connect the probes at the indicated point from figure in the
given trainer kit.
(3) Observe the waveforms at different points using C.R.O.
(4) Draw the observed waveforms.

(3) BM – BPF Output (4) Output Amplifier.

CONCLUSION :

CIRCUIT DIAGRAM :

Audio 1 MHz
Oscillator 455 KHz
Crystal
Amplifier Oscillator
Oscillator
Frequency

(1) (2) Antenna

(3) Output (4)
Audio Balance BM BPF
Amplifier Ceramic BPF Amplifier
Modulator Balance
Gain

Speaker



SSB - AM RECEIVER

AIM : To study the working of Single Side Band Amplitude Modulation
(SSB-AM) Receiver.

APPARATUS : (1) SSB AM Trainer Kit
(2) Model No. ST2201 for transmitter, ST 2202 for
Receiver
(4) Power Cord.
(5) C.R.O.
(6) C.R.O. Probes.

PROCEDURE : (1) Connect the probes at the indicated point from figure in the
given trainer kit.
on C.R.O.
(4) Adjust gain and frequecy properly at different points. And try
to get the recovered audio signal same as input.

(5) Product Detector Output (6) Audio Amplifier Output.

CONCLUSION :

CIRCUIT DIAGRAM :

Antenna

RF Amp Product Audio Amp
Mixer IF Ampr-1 IF Ampr-2
Gain Detector Gain

Beat Freqn Speaker
Tuning Local Osc
Osc



FM TRANSMITTER
AIM : To study Frequency Modulation (FM) Transmitter.

APPARATUS : (1) Trainer kit: Model ST 2203.
(2) Connecting Probes
(3) CRO
(4) CRO Probes.
(5) Power Cord.
PROCEDURE : (1) Connect the links in the circuit as shown in the circuit
diagram.
(2) Switch ‘ON’ the supply.
(3) Now observe the FM transmitted wave on CRO.
(4) Draw the waveforms.
CONCLUSION :

(3) FM Modulated Output (4) Output Amplifier.

Information Signal

Audio
Oscillator FM output

FM Modulator
Varactor/ Output
Reactance Amplifier

Carrier
Generator


.
FM RECEIVER

AIM : To study Frequency Modulation (FM) Receiver.

APPARATUS : (1) Trainer kit: Model ST 2203.
(2) Connecting Probes
(3) CRO
(4) CRO Probes.
(5) Power Cords.

PROCEDURE : (1) Connect the transmitter output to receiver input
(3) Now observe the FM transmitted wave on CRO.
(4) Now observe the received waveform on CRO.

(5) Demodulated Output (6) Audio Amplifier Output.

CONCLUSION :


FM input FM Detector
Foster Seeley/ Audio
Amplitude LPF +
Ratio/ output
Limiter Amplifier
PLL/
Detuned Resonant Circuit



SAMPLING & RECONSTRUCTION CIRCUIT

AIM : To study the sampling and reconstruction circuits.

APPARATUS : (1) Trainer Kit (Model ST 2101)
(3) Power Cords.
(4) CRO
(5) CRO Probes.

PROCEDURE : (1) Connect the probes at the indicated points from figure in the
given trainer kit.
the sampled signal.
on CRO and note working of the circuits.
(4) Watch the reconstruction of the signal at the output and
observe the signal on CRO.

GRAPH : (1) Analog Signal (2) Sampling Pulses
(3) Sample Output (4) Sample and Hold Output
(5) Second order LPF Output (6) Forth Order LPF Output.
For Different Sampling Frequencies.

CONCLUSION :


Sampling Circuit
Sampling Sample
Frequency Duty Cycle (2) Output
+1 Second Order (5)
Selection Control Circuit LPF
Circuit (3)
(2K,4K,8K, Buffer
16K, 32K) Hz

Buffer
(4)
4th Order LPF
Signal Buffer (6) output
Generator 1KHz (1)

Analog
Signal Sample and
Hold Output



TDM-PCM TRANSMITTER AND RECEIVER

AIM : To study the working of TDM-PCM (Time Division Multiplexing-
Pulse Code Modulation) Transmitter and Receiver

APPARATUS : (1) TDM-PCM Trainer Kit. ST-2103 and 2104
(2) Connecting Probe
(3) Power Cords
(4) C.R.O.
(5) CRO Probes.

PROCEDURE : (1) Connect the probes properly in the circuits according to the
diagram of TDM-PCM as shown.
(3) From function generator, apply DC as well as different
frequency AC signals one by one,
(4) Select a data to be transmitted.
(5) Observe the received data at the receiver side and observe the
waveforms on the CRO also.
(6) Now select parity odd and observe the error detection at
receiver side.
(7) Now select parity even and observe error detection at
receiver side.

GRAPH : (1) Transmitted Data (2) Received Data without Parity
(3) Received Data With Even Parity (4) Received Data With
Odd Parity

CONCLUSION :

CIRCUIT DIAGRAM:



SETTING UP FIBER OPTIC ANALOG AND DIGITAL LINK
AIM : To study a 650 mm fiber optic analog and digital link- the
relationship between the input signal and received signal.

APPARATUS : (1) Trainer Kit. ST-2501
(2) Connecting Probe
(3) Power Cords
(4) C. R. O.
(5) Optical Fiber.

PROCEDURE
(1) Connect the power supply to the board.
(2) Ensure that all switched faults are off.
(3) Make the following connections. (As shown in diagram 1).
(a) Connect the function generator 1 KHz sine wave
output to emitters’ input.
(b) Connect the fiber optic cable between emitter output
and detectors’ input.
(c) Detector output to AC Amplifier input.
(4) On the board, switch emitter driver to Analog mode.
(5) Switch ON the power.
(6) Observe the input to emitter (t.p. 5) with the output from AC
Amplifier (t.p. 19) and note that the two signals are same.
(7) Connect the function generator 1 KHz square wave output to
emitters’ input.
(8) Repeat the procedure by switching emitter driver to Digital
mode and follow the diagram 2 for connections.

GRAPH : (1) Transmitted Signal (2) Received Signal for both cases

CONCLUSION :

CIRCUIT DIAGRAM:

Fig. 1

Fig. 2



TELEVISION SIGNAL PATTERN GENERATOR
AIM : To study television signal pattern generator and to obtain different
patterns on color TV receiver.

APPARATUS : (1) Color TV receiver
(2) Pattern generator
(3) Connecting cables
(4) C. R. O.

THEORY :
Front panel of pattern generator:-

Control sockets and their functions of pattern generator.
1. Pattern Selector:-
This is a 12 way switch used for selecting the requisite patterns. (The indicated
patterns will be available from the RF and Video outputs only when the push button switch
4 is in the out position.)
2. CH 4 / IF-RF:-
This push button is used in conjunction with switch 2a below and is used to select
the IF or CH4 output, available at connector 8.
2a. CH selector:-
This comprises of a two way rotary switch and a multiturn potentiometer. When
switch is set to CH5-CH12 the potentiometer can be adjusted to any desired channels
between CH5 and CH12. For making this adjustment connects a TV to a known
transmission channel or CATV channel. Then connect the RF output and fine tune the

potentiometer for a stable pattern display. This adjustment may have to be verified from
time to time.
3. 5.5 MHz ON/OFF sound:-
The 5.5 MHz sound carrier which is FM modulated by 1 KHz sine wave can be put
ON/OFF by this switch.
4. 1 KHz / EXT (DECODER) sound:-
This has dual function one in sound and other in chroma. If external sound
modulation is required then set the Pattern selector switch to any position of the three black
and white (B/W) patterns and press button 4. By releasing the button, internal 1 KHz
will modulate the RF signal. If the Pattern selector is set to any of the colour pattern and
the above procedure is followed, then the colour will disappear.
5. ON / OFF Burst:-
This push button will enable/disable the burst in the video signal. This feature is used
in troubleshooting the colour killer circuitry of the TV receiver.
6. ON / OFF Rhombus:-
This pattern is very useful for adjustment of the aspect ratio of the picture and also the
linearity. This pattern can be superimposed on any of the patterns selected by the Pattern
Selector. The linearity is best adjusted when this pattern is superimposed on the crosshatch
pattern.
7. ON / OFF Mains:-
This switch connects/disconnects power to the generator. An LED indicates when
power is on.
8. Output RF:-
This is a co-axial output for the RF signal. This output should be connected to the TV
by 75 cable.
9. Attenuator RF:-
This is a switched attenuator with a total attenuation of 75 dB approx. in steps of -
10 dB, -5 dB and 3× -20 dB. These switches can be used in any combination to provide the
most suitable signal output required. It is possible to compare the sensitivity of various TV
sets from point of view of gain, colour loss threshold, sync loss threshold, presence or
absence of oscillations etc. by judicious use of the attenuator. The attenuator is optimized
for IF and CH4 with inaccuracy being about 3 dB in 75 dB attenuation. The attenuator is
also very useful in isolating faults specially related to gain in the IF section of the TV
receiver.

10. Earth:-
The instrument earth connection is used along with sockets 11, 12, 13 as the earth
return path for the signal.
11. EXT Audio IN:-
2mm socket for connecting the external audio input, the switch 4 should be set to
EXT (refer 4 above). The usable range is 200 Hz to 7 KHz approximately. This feature is
very useful for checking out the loud speaker rattling and also for loose hardware or
component inside the cabinet.
12. Line Trig / Frame Trig :-
Line and frame sync signals are available separately at these sockets. These outputs
can be used to externally synchronies the oscilloscope which will ease triggering;
especially when the sweep rates are varied.
13. Video Output:-
Fixed video output of 1 V (p-p) is available at this socket when the output is
terminated in 75 . Care should be taken to ensure that no voltage is fed into this socket as
this may damage the equipment.
14. Sound Output:-
5.5 MHz carrier along with the 1 KHz modulation is available at this co-axial socket.
The effect of all combinations of the various switches affecting the sound will be reflected
on this output. This output can be used for adjusting the 5.5 MHz coils/traps in the TV
receiver.

Applications of various test patterns.
1. Dot pattern:-
It is used mainly for checking static convergence in a CTV. The dots should be pure
whit on black background. Presence of more than one colour implies that one or more
electron beam is passing the wrong hole in the shadow mask.
2. Cross Hatch Pattern:-
This is mainly used for checking and aligning the dynamic and corner convergence of
the picture tube. i.e. Pincushion Correction
3. Checkerboard Pattern:-
It is a visual quick check for centering, focus and vertical & horizontal linearity. The
transition from black to white and white to black gives an indication of the bandwidth.
These transitions should be sharp. Vertical lines at the transitions are an indication of

ringing, gray zone is an indication of poor bandwidth. Hum interference on
synchronization is also visible on this pattern as waviness at the transitions.
4. Colour Bar Pattern:-
It is a standard colour bar. The vertical bars are white, yellow, cyan, magenta, red,
blue & black. This pattern provides sufficient check for a good overall check on a CTV
performance; such as burst keying, subscriber regeneration, RGB amplifiers, delay versus
B/W signal and saturation check.
5. White Pattern:-
It can be used for white setting and check of colour purity. This pattern can also be
used for making the maximum beam current adjustment.
6. Purity Patterns:-
These patterns can be used for checking colour purity as well as to ensure that there is
no interference between sound and chroma carrier. The red pattern is generally used for
colour purity checks. In a properly adjusted TV sets the electron beam will strike only one
set of colour dots or stripes on the TV screen. With red pattern only red colour should be
visible, if any other colour is present than colour purity needs adjustment.
7. Black Pattern:-
Black pattern indicates no video information. No video information can be used to
check the front and back porches the sync pulses.
8. Linearity pattern:-
It is generally used to adjust height and width so that the TV delivers a picture with
the correct aspect ratio of 4:3. It can be superimposed on any pattern. The pattern consists
of a rhombus with two diagonal lines. For correct adjustment the corners of the rhombus
should just touch the sides and the diagonal lines should pass through the corners of the
picture tube.
Normally the linearity pattern is superimposed on the crosshatch pattern for the
adjustment.
With the linearity pattern on keep changing the patterns from colour bar red, blue…
so on. The size of the rhombus may change slightly with different colours. If the change is
pronounced it implies that the EHT regulation is poor thereby the picture quality will be
affected depending on the colour content.

PROCEDURE:

1. Connect the output of the pattern generator using RF cable to the TV set.
2. Observe the different video pattern generated by pattern generator on the TV set.
3. Connect the Video output of the pattern generator using probe to the CRO input.
4. Observe the different waveforms of the video signal on the CRO.
5. Draw the different waveforms of composite video signal.

GRAPH : Composite video Signal for monochrome and color signal pattern

CONCLUSION :


COMMUNICATION ENGINEERING ASSIGNMENT(INSTITUTE ELECTIVE-1) SEM-4 SVMIT

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