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Magnitude comparator trainer is intended to study the comparison between two binary number systems. It is used to determine the weight-age of two binary numbers and decide which number is (a) equal = (b) less than < or (c) greater than > the other number. This is an important concept that is used extensively in digital communications systems. This comparison is analogues to

determine which car is running faster than the other or which is cheaper than the other etc. Of-course one has to decide this after due consideration of comparing other operating parameters also. The application of magnitude comparison is very wide in nature and the limit is only imagination and innovation.

For example, the result of such a comparison is used to set the duty cycle of a clock signal that is used to generate synchronization signal. Therefore it is necessary to understand what this magnitude comparator is all about. The scope of this trainer restricts itself in experimenting to find out upto the comparisons only.

This trainer uses 8-bit magnitude comparator as basic building block. The necessary signal generation is accomplished by using switches as inputs and LEDs as output indicators. This trainer uses two sets of BCD thumbwheel switches as inputs. One set of two (the first switch in units position, the other in tens position) switches-A, act as a comparing input while the other set of two switches-B, as compared number. There by allowing you to set numbers in the range of 0 to 9910, as inputs to the comparator. There are two numbers of 4 bit magnitude comparators, with a provision to cascade the outputs of first block with the inputs of next block, thus allowing you to make an 8bit comparator system. This trainer has other associated electronics also as part of the experimental setup.

Antenna System Laboratory is a very useful acquisition for any modern Electronics & Communications Laboratory. It can be used to practically demonstrate the basic principles of EM Theory.

Introduction:

What is an Antenna?
An antenna is a wire or a group of wires. It converts RF signals, generated by the transmitter, into electromagnetic waves for propagation through space. The receiving antenna receives these EM waves and reconverts them back into the original RF signals for further processing.
The antennas act like interfacing devices between a transmitter and space, and also between space and a receiver.
Thus, both transmitting and receiving antennas have entirely different functions to perform. But they also behave identically (i, e), their behavior is reciprocal.
Any communication system is as good as the antenna it uses. It is completely self-contained for conducting all experiments.
Using ASL-1, the student can understand the basic principles of polarization, directivity, gain and impedance of various types of antennas, in a laboratory environment. In reality, an antenna is a very complex device, with distributed components like inductance, capacitance and resistance spreading all over its length and breath.
They also vary continuously all over its surface and their spread determines the polarization, gain and radiation pattern etc., of an antenna.
Thus, an antenna is an LCR network.
The student can verify them in the laboratory.
Each antenna has its own special features and applications. There is no one best antenna design for all purposes.
Only about 70 types of antenna seem to have been developed so far in the world. Today, 90% of all antennas are vertical, 5% horizontal and 5% other types.

Objectives of Experiments:

Description:
Antenna System Laboratory consists of thirty varieties of antennas fabricated in several shapes and sizes, depending upon the operating frequencies and applications.
a) Eight Stands,
b) One Adjustable TRIPOD,
c) A VHF transmitter (1.5 watts power) with a frequency of about 135-175MHz is supplied for exciting these antennas.
d) One tuned VHF field strength meter. (FSM)
e) One untuned VHF field strength meter. (FSM)
f) VHF Amplifier
g) DIP Meter
h) Voltage Standing Wave Ratio (VSWR) meter.
i) 10meters of coaxial cable, having 50-ohms impedance.
j) A set of ten cables.
k) A detailed instruction manual, for conducting experiments.
Compact Disc (CD):
Compact disc is supplied to understand the details of all thirty antennae. This is simulation software. This is optional requirement. A compact disc (CD), to understand details of all thirty antennas.

Description of the system:
The following antennas are supplied with the ASL-1. Using these antennas, it is possible to study the behavior of each of them for a given transmission and reception medium. The antenna is mounted on a revolving stand. This stand can be manually revolved on a horizontal axis in 3600 with reference to ground plane. It is possible to record and observe the response on a field strength meter (FSM). Using these readings it is possible to draw the POLAR diagram for various angular positions of antenna. Each antenna is a dynamic demonstrator by itself.

Types of antennae supplied are:
1. Vertically Polarized Antenna.
2. Horizontally Polarized Antenna.
3. Circularly Polarized Antenna.
4. Quarter Wave Antenna.
5. Grounded Vertical Antenna.
6. Vertical Half-Wave Dipole Antenna.
7. Horizontal Half-Wave Dipole Antenna.
8. Full Wave Dipole Antenna.
9. Yagi Antenna
A) Folded dipole
B) Folded dipole, with a reflector
C) Folded dipole, with reflector and three directors
10. A loop (frame) Antenna.
11. Quad Loop Antenna.
12. Circular Loop Antenna.
13. AD Cock Antenna.
14. Ferrite Rod Antenna.
15. Helical Antenna.
16. Rhombic Antenna.
17. Endfire Antenna.
18. Broadside Antenna.
19. Collinear Antenna.
20. Log-Periodic Antenna.
21. Top-loaded Antenna.
22. Spiral Antenna.
23. Biconical Antenna.
24. Dipole Antenna, with corner reflector.
25. Turnstile Antenna,
26. Super turnstile Antenna,
27. Batwing Antenna,
28. Discone Antenna,
29. Slot Antenna,
30. Flush Disc Antenna,
31. Cellular Antenna,
32. Pager Antenna,
33. FM Antenna,
34. Horn Antenna,
35. V-Antenna,
36. Active Antenna,
37. Transmission Lines and a probe.

VHF Transmitter: This is a hand-held, variable frequency (135MHz to 175MHz) with 1.5 Watts of VHF output. It can be used both in the field and laboratory environments. It uses a re-chargeable battery. Any ?LOW? battery status is indicated, for recharging.
This PLL synthesized digital transmitter has a 4-digit frequency counter, with a 100 KHz resolution.
Its frequency can be varied by both SLOW/FAST controls. It can be modulated externally using a condenser microphone.

Tuned VHF Field Strength meter: This measures RF level of each received signal in mV, (between 1dB to 100dB) in steps of 1dB. This is also battery operated. Convenient for field/laboratory uses.

Tripod: This is used to mount transmitter antenna. This is fixed on a stand, whose height can be varied upto 2 Meters.

Software: This is an optional requirement. Using this simulated software, it is possible to plot radiation patterns on the computer.

What can a student learn? Using this trainer: The following are the objectives. After performing the following listed experiments the student learns
a. The evolution of antenna
b. Understand the current and voltage distributions along its entire length of transmission line and find its characteristic impedance.
c. Measure voltage and current distributions along the length and breadth of antenna.
d. Prepare a perfect earthing system, (an earth mat) or a simulated ground.
e. Understand types of polarization (vertical, horizontal and circular)
f. Understanding the field strength, radiation pattern, power gain and impedance of antennas.
g. Design a half wave dipole for a given frequency.
h. Understand the effect of perfect ground as a reflector.
i. Understand the principle of reciprocity.
j. Understand the principle of directional antennas, for navigational purposes.
k. Understand the effect of reflector and each director in a Yagi Antenna, in terms of gain and radiation pattern.
l. Determine the right type of BALUN.
m. Design at least ten types of antennas and construct them.

List of Experiments:

1) Determination of plane of polarization
2) Measurement of gain
3) Drawing of radiation pattern
4) Calculation of impedance.

Delta modulation is the process of converting the message signal x(t) in 1-bit (two level) quantizer form, ie; ? ?. The correlation between the adjacent signals is increased purposely. In this way the prediction, there by the quantization error can me small.

Using this trainer it is possible to study modulated step size ? at the integrator output and compare with the calculated value. It is possible to compare the message signal and integrator output and analysis can be made on this observation. It is possible to observe the occurrence of granular noise, and slope overload noise as a function of variable parameter.

The following responses can be observed for the above functions, by varying the Message amplitude. By varying the sampling frequency. By using a total harmonic distortion (TDH) analyzer it is possible to measure the % of harmonic distortion. It is also possible to plot the THD by measuring the message signal frequency fc, Amplitude fa, ? step size, and the sampling frequency fs.

This instrument requires an external function generator in the rang eof 100 to 10KHz with PtoP amplitude of 8V, a dual beam Oscilloscope, an true RMS voltmeter.

Digital Satellite Receiver Communications Trainer Model SAT-1 is a dynamic demonstrator. It is intended to study the various blocks in a typical Satellite receiver. Wherever possible test signal points are provided. This trainer receives QPSK satellite broadcasting RF signal and decodes the digitally encoded signal. This has digital tuner with Loop-throughput. SCPC/MCPC receivable from C / Ku band Satellite. This has the following controls on the trainer. They are Power button, Menu select button, Channel scroll function, a remote handheld unit, 6 feet dish antenna (bigger size antenna can be provide at optional cost), Low Noise Block converter (LNB), This trainer has an RS232C serial port facility to connect PC to your home TV receiver.

Specifications:
1. Tuner & Channel

• Type : 1x F-type, IEC 169-24 Female
  
• Frequency Range : 950MHz to 2150Mhz
  
• Input Impedance : 75 ohm unbalanced
  
• Signal Level : -25 to ?65dBM
  
• LNB Power : 1305/18.5V DC?5%, 0.5Amax, Overload protected
  
• 22Khz Tone : Frequency: 22KHz?2KHz Amplitude: 0.6V?0.2V
  
• DisEqc Control : Version1.2 Compatible
  
• Demodulation : QPSK
  
• Input Symbol Rate : 2-45Ms/s
  
• FEC Decoder : Convolution Code Rate 1/2, 2/3, ?, 5/6 and 7/8 with
  constranit Length K=7

2. MPEG Transport Stream & A/V Decoding

• Transport Stream : MPEG-2 ISO/IEC 13818 Transport Stream
  
• Profile Level : MPEG-2 MP@ML
  
• Input Rate : Max 60Mbit/s
  
• Aspect Ratio : 4:3, 16:9
  
• Frame Rate : 25Hz for PAL, 30Hz for NTSC
  
• Video Resolution : 720 x 576(PAL), 720 x 480(NTSC)
  
• Teletext : Through VBI & OSD
  
• Audio Decoding : MPEG/MusiCam Layer I & II, MP3 AC3
  
• Audio Mode : Single channel / Dual channel Joint Stereo / Stereo
  
• Frequency Response : 20Hz?20KHZ, ?2dB
  60Hz ? 18KHZ, ?0.5dB
  
• Sampling Rate : 32, 44.1, 48KHz

3. A/V & Data In/Out

• RCA Output : CVBS (Yellow), L, ROutput (White, Red) with Volume Control
  
• Data Interface : RS-232, Bit Rate: 115200baud
  
• Connector : 9-Pin D-Sub Male type

4. Power Supply

• Input Voltage : AC 90 ? 260V, 50Hz ? 60Hz
  
• Power Consumption : Max. 40W
  
• Stand-by Power : ?=7W
  
• Protection : Separate Internal Fuse
  
• The input shall have the lightning protection

5. Environmental Condition

• Operating Temperature : 0 ? 400C
  
• Storage Temperature : -100C ? 500C
  
• Operating Humidity Range : 10 ? 85%RH, Non-condensing
  
• Storage Humidity Range : 5 ? 90%RH, Non-condensing

Cable: 25 Meter suitable cable required to connect your Antenna dish to the trainer is supplied.

OPTIONAL: Optional, remote servo motor controller for dish positioning with necessary Digital satellite equipment controller. It is necessary to AIM, exact position of the dish to correct Longitude, Azimuth and center point of the transmitting satellite for proper viewing.

NOTE1: Scope of supply does not include the supply of Television receiver. Normal home TV is adequate to view the satellite channel programs.

NOTE2: Several commercial satellite channels are pay channels. Therefore the reception of these channels cannot be viewed unless paid for to the operators.

Frequency modulation is by far the most important communication means. This finds an application in transmitting systems. This is preferred, because of its ability to eliminate associated noise, there by providing high fidelity in the audio at the receiving end.

This trainer is to understand the concept of

generating a FM signal for further analysis. This trainer requires a modulating signal, often called as message signal. This can be a SINE wave generated by an external audio generator as one input. The carrier wave is generated by the internal electronics in the trainer itself. By using an external Oscilloscope the FM wave can be observed at its output terminals. This has a built-in demodulation setup, which reconstructs the message signal and is available for observation. You can use this trainer to measure the modulation index.

Frequency shift keying (FSK) is a form of FM that, with minor exceptions. The modulating signal is a digital voltage (code 1?s and 0?s) that will key the carrier to shift between only two distinct, fixed frequencies. In this case, the low frequency represents a digital 1(mark), and the higher carrier frequency is a 0 (space). The second variation from standard is that the carrier is not much higher in frequency than the frequency of a encoded message signal.

This trainer is a demonstration unit. In this trainer, the signal to be modulated namely Sine, Square or any other signal in the range of 100Hz to 2KHz with 1-2 V Peak to Peak is applied as input to the modulating input terminal. The built-in clock generator provides the required sampling rate. It is possible to change this clock frequency by patch cording necessary RC combinations. Thus the signal to be modulated is sampled now. The FSK modem converts this into series of pulses as output after locking takes place. This signal is further processed and a Frequency Shift Keyed output is available at the demodulating output terminal.

This FSK signal is further processed through a signal reconstructor circuit and the actual signal is available at the output terminals for observation.

Thus various waveforms namely modulating signal, sampling clock, FSK modulated signal, Demodulated signal, reconstructed signal can be viewed on an external Oscilloscope for measurements.

This trainer is assembled in an ergonomically designed cabinet, with necessary power supplies, test points for observations. This require an external function generator and an 20MHz oscilloscope for measurements.

Line coding demonstrator is intended to demonstrate the principles of LINE CODING. In digital transmission of data, over wire or optical fiber systems, the digital data is transmitted in binary form after proper signal conditioning. The data so transmitted must be securely received, at the intended receiving station. In order to accomplish this function, several schemes are designed and adopted. One such a scheme is called as LINE CODING. There are many methods in line-coding formats. Each one of the methods offers one or more of the following advantages over the other. For example, (a) the line coding is used in telephone line applications for spectrum shaping. (b) This is also used to recover bit clock for synchronization with the received signals. (c) To eliminate DC component, that is likely to accompany with the received signal, which otherwise introduce base line wandering. (d) To increase the bandwidth, of transmitted data, compared to other schemes.

Using this trainer the student can observe waveform of a selected scheme as described below, using an oscilloscope.

The schemes available on this trainer are:
a. Unipolar Non Return Zero (NRZ)
b. Unipolar Return Zero (RZ)
c. Polar Non Return Zero
d. Polar Return Zero
e. Bi-Polar Non Return Zero and
f. Bi-Polar Return Zero.

In order to accomplish this the trainer has a built in sequence generator, and necessary building blocks for conducting one of the above schemes. It is necessary to connect an external square wave generator as input to the sequence generator with at-least 100KHz at TTL levels. This instrument has built-in power supply.

Microwaves today affect everyone. You may not realize it, but each day your life is made better by man's ability to utilize microwaves. When you make a telephone call across the country or watch television from your armchair, microwaves help you. Satellites circling the earth are exchanging information millions of times every day through microwave transmission. Communications, health care, national security, alarm systems, the police officer clocking the speed of your car - all require microwave technology. This phenomenon has created many new jobs and extensive need for technicians and engineers. You will learn some of the important principles and techniques of microwaves.

Some of the typical experiments that can be conducted using this trainer are:

1) Measurement of Microwave power.
2) Measurement of VSWR.
3) Measurement of Frequency and wavelength.
4) Measurement of Impedance.
5) Waveguide Attenuators.
6) Klystron Characteristics.
7) Microwave tuners.
8) Directional couplers.
9) Series Tees and Shunt Tees.
10) Microwave Detectors and Mixers.
11) Reflection Loss within a Waveguide.
12) Propagation of Microwaves.
13) Primary Microwave Antennas.

Specifications:

• Microwave RF source.
  
• Waveguide attenuators.
  
• Slotted line with probe and detectors.
  
• DC microammeter
  
• Short circuit terminator
  
• Waveguide stands.
  
• Thermistor mount.
  
• RF attenuates.
  
• 1000 (1% metal film, 1/2 watt resistors.
  
• 0 - 30V DC power supply
  
• Volt-Ohm meter.

Phase Shift Key (PSK) Modulation is a form of Binary Digital Modulation. The modulation process corresponds to a scheme of switching or keying the amplitude, frequency or phase of the carrier wave between Ones and Zeros. The result of this yields three different methods of modulation, they are FSK, ASK and PSK. In Phase shift key technique, a message signal of fixed amplitude and fixed carrier wave is used to denote Ones and Zeros. The phase of carrier and the message differs by 1800

It is represented in the form of
S(t) = Ac . cos(2?fct) to represent Logic 1 and
S(t) = Ac . cos(2?fct + ?) to represent Logic 1

In this trainer, necessary blocks with components are available to accomplish the above task. This unit requires an additional function generator and pulse generator in the range of 100Hz to 100KHz. An external dual beam Oscilloscope is required to observe the input output waveforms. The entire instrument is assembled in an ergonomically designed FRP cabinet.

Pseudo Random Bit Sequence is used to scramble data in a communication system for security reasons. Some of the applications are in Cryptography, computer data security and integrity, prevent unauthorized usage of cable TV line by scrambling data, generating elaborate tonal structures unlike any known instrument, instrument voicing etc.

These sequencers have several nice features. First they can be of maximal length, that is they can be as long as a register sequence can possibly be. This turns out to be one less than 2n, so that the circuit is essentially as efficient as a binary counter. Second, the number appears in an apparently random order, although, of course they repeat every time the sequence is clocked completely through 2n-1 counts. The same noise pattern repeats every n-1 clock cycles. This is used for testing audio systems. In fact pseudo noise turnout to be better than real noise. The randomness is complete over one total cycle, where real noise requires a very long (ideally infinite) time average to get true randomness.

This PRBS generator makes use of 63-state count using 6 registers. The binary outputs of this sequencer are processed to obtain random analog levels. As a result of this a series of uniformly timed steps of random analog values can be generated. This can be used to test a musical system. It is possible to change the bit sequence by changing the count sequence using patch chords.

This trainer is same as Fiber Optic Pulse code modulation trainer Model FOT-7. The only difference in PCM-1 is that a connecting patch cord is used instead of Fiber Optic cable. Otherwise it is the same as FOT-7.

The purpose of this trainer Model PCM-1 is to introduce you to the Pulse Code Modulation (PCM) and demodulation technique. A multimode Fiber Optic cable is used for data transmission and reception. In this trainer, you will understand and investigate the following processes. All the major blocks of this trainer are designed from fundamental building blocks instead of using a dedicated CODEC. As a result, all the blocks of CODEC are dissected and are available as separate building blocks for study. This facilitates the student to understand the quantization process and view the quantified and encoded data using 8 bit LED displays at the transmission side. Observe the serial transmission and reception of this quantified decoded data at a test point, observe the decoded 8 bit received data on LED display etc. This data is further reconstructed and the original signal is available at an output terminal for analysis. As a result of this design, the student can see various stages of the PCM transmission and reception processes for himself.

Features of PCM blocks are

• Digitization of an analog signal,
  
• Observe the quantization (encoding) of incoming signal,
  
• Measurement of quantization noise,
  
• Serialization of quantized signal for onward transmission,
  
• Serial data capture,
  
• Decoding of quantified signal,
  
• Observation of received signal,
  
• Reconstruction of received signal, and
  
• Study of aliasing.

In order to achieve the above, the trainer has necessary built in input signal sources.
a) Continuously variable analog input in the range of 0 to 5 VDC,
b) Function generator with Sine, and Square wave inputs in the range of 200Hz to 20KHz
c) Microphone input after proper signal conditioning, for voice transmission and
d) Provision to connect an external signal source.

The output of the transmitted and received signals, decoded signal and finally the reconstructed outputs can be observed on the oscilloscope.

In order to observe the sequence of events taking place, there are two types of clocks provided, one operating at 200KHz, the other at 1Hz. During slow clocking it is possible to observe the signal flow at various test points as detailed below.

a) Quantization process
b) Serial transmission
c) Decoded output and
d) Reconstructed output.
e) A power amplifier with speaker to hear the voice reception ( when sampled at 200KHz)

This trainer comes with completely self-contained systems with built-in power supplies, signal sources, input output test points for signal observations, a microphone with proper signal condition, a power amplifier with speaker etc. This requires an optional external Dual beam oscilloscope to observe the PCM signal transmission at different stages of modulation and demodulation processes.

Specifications:
Input sources:

1. Built-in Function generator with SINE, and SQUARE waveforms.
2. Frequency: Variable frequency of 200Hz to 2KHz
3. Amplitude: Variable in the range of 0 to 5 Volts
4. Continuously variable DC source : 0 to 5V DC
5. Provision for connecting external signal source

Output:

1. 8 bit LEDs to display Quantized data
2. 8 bit LEDs to display decoded data
3. Power amplifier with speaker
4. Frame timing LED to display clock signal
5. Synchronizing signal LED
Built-in power supplies. All the above are available in an ergonomically designed cabinet.

PWM: Pulse Width Modulation is the process of modulating an analog signal usually voice frequency in the form of variation of pulse width proportional to the voice (or signal) amplitude. The voice frequency is modulated on an internally generated carrier wave. The reconstruction process of this wave is by demodulating and original voice signal is recovered. This trainer requires an external function generator with 1 KHz frequency and 1 V P toP signal strength. Using a dual beam oscilloscope it is possible to observe the input signal, modulating signal and demodulating signals.

PAM: Pulse amplitude modulation is a type of modulation is used as the first step in converting an analog signal to a discrete signal or in cases where it may be difficult to change the frequency or phase of the carrier. In this case the carrier is a pulse train rather than a sine wave and the spectrum of the carrier consists of several components at nwc = 2np/T where T is the time between pulses.

Using this trainer it is possible to observe the modulated PAM signal and demodulated message signals on the Oscilloscope. It is necessary to study the effect of sampling pulse duration, sampling rate on the PAM signal and on the demodulated signal. Be sure to reduce your sampling frequency such that your sampling frequency is below Nyquist rate.

PPM: Pulse position modulation makes use of PWM signal generated during PWM setup as input for modulation purposes.

This is a 3 in 1-modulation trainer. This trainer is intended to study the basic principles of Pulse Modulation techniques. This provides a unique opportunity to construct a complete modulation setup required in a communication system. This can be best studied and experimented in the audio range. This requires two independent external function generators as necessary sources for generating carrier and signal. This trainer has all the necessary active and passive components required to perform the experiments, and built-in power supply. The output waveforms can be monitored on an external CRO. You need an external function generator, a pulse generator operating in the range of 100 Hz to 100KHz, and an Oscilloscope for observing the waveforms.

The Time Division Multiplexing (TDM) is a method to use the same transmitting channel to transmit messages coming from different sources as its input. The number of message channels that a TDM system can handle successfully depends on the cycle frequency of the TDM switcher. In order to have loss-less transmission of all the messages, the switching frequency of the TDM system, must be much higher switching frequency than, any of the message signal frequencies. This illustrates how time spanision multiplexing takes place.

This TDM trainer can handle two message channels. This trainer has built in pulse generator, which is used as TDM switch for time spanision multiplexing. Two different message signals must be connected as input to this TDM trainer from external function generator of 1 KHz. The message signals can be SINE, SQUARE, RAMP etc. An external oscilloscope is an important requisite for the experiment. This trainer has blocks consisting of clock generator, Channel selector, time spanision multiplexer, in addition to built-in power supplies. The necessary connections are established using 22SWG wire patch-cords.