EB-170 AM Communications Circuits

Innovative Technologies in Education (ITE)

EB-170 AM Communications Circuits

EB-170 is a single board comprehensive instructional module designed to teach the basic concepts of amplitude modulation (AM) communications to technology students in technician and engineering training programs. The module can be operated as a stand-alone unit or as part of the EB-2000 Computer Managed Laboratory (CML). The module contains an AM transmitter and broadcast band receiver that allows the student to perform a number of meaningful practical experiments at various levels of difficulty. Manual or computer driven fault-finding exercises and testing are available when the board is connected to the PU-2000 mainframe. Measurements are performed by connecting test equipment to the 2mm jacks, placed at various test points related to the circuits on the board. Students need to perform a minimal amount of wiring, so that the effective training time is minimised. A comprehensive student manual is provided with each training module. The manual relates to the technological subjects covered enabling a focus on the specific objectives of each experiment. Courseware that runs on IBM-PC or compatible computers can enhance the experiment manual by checking the student's response to questions and measurements. The optional CML software enables the instructor to monitor each student's achievements and store them in the database at the instructor's station.

DESCRIPTION

The EB-170 module is designed so students will spend the maximum time on the experiments and practice drills for testing comprehension and troubleshooting. The module also ensures that students use their time more efficiently. The printed circuit boards are pre-wired so that set-up time is minimal. For operation the module is connected to a PUZ-2000. To facilitate the exercises, all the major signals are brought out on-board with 2mm jacks for tests and interconnections. The ICs and the transistors are mounted on sockets, enabling easy replacement. The student has only to plug-in the appropriate patching cords and shorting plugs in order to perform the recommended experiments. The boards also come equipped with "black boxes" containing components used in the fault-finding and practice modes, components that should not be visually identified by the trainee.

RECOMMENDED EXPERIMENTS
Signal Sources -
Observe RF signal generator amplitude & frequency range

Observe local oscillator signal shape, frequency and function

AM Modulation with a Multiplier -
Multiplier as a modulator

Modulated output for different levels of modulation

Modulation with triangular and square waves

Carrier suppression and varying modulation level in DSB/SC modulation

RF Tuned Amplifier -
RF tuning with a variable capacitive diode

Measure RF tuned amplifier performance

IF Mixer -
IF mixer operation

IF filter bandwidth

IF mixer selectivity

Image frequency of IF mixer

Effect of modulating signal frequency on modulation level

IF Amplifier with AGC -
IF amplifier operation

Effect of IF amplification on AGC voltage

Envelope Detection & AGC Amplification -
Envelope detector operation with sine, triangle and square waves

DC and AC components of detector output, effect of carrier & modulation levels

Effect of filter time constant on detector operation

Effect of diode type on detector fidelity

Effect of AGC feedback loop on envelope detector and AGC amplifier

Superheterodyne Receiver Performance -
Understand receiver block diagram

Tuning the receiver to a desired signal

Measure signals at various stages of the receiver

Check detector fidelity

Check receiver bandpass band

Check AGC operation

Receive local AM stations

REQUIRED ACCESSORIES
TK DMM Multimeter

Model 112B Oscilloscope

Model 113B Frequency Counter

Model 141 Function Generator

PU/PUZ2000 Mainframe

DL-20 Standard set of 2mm Patching Cords and Shorting Plugs

Optional Accessories -
EB-170SW Courseware

MANUAL
Student and instructor manuals, written by pedagogues and electronics professionals, support every stage of the learning and teaching process.

The optional EB-I70SW courseware enriches the student manual by adding self-test questions before performing each experiment and observation questions to test the student's comprehension.

The optional software automatically tests all measurements while the student performs each experiment activity.