Practical # 1

THE DIPOLE IN FREE SPACE

OBJECTIVESInvestigate the polar plots of a dipole in free space

PROCEDUREConnect the hardware as described in operator’s manual.Load the discovery software.

IntroductionThe simplest form of antenna is called a dipole. This is a conductor that is divided in the middle and connected to a feeder which connects the antenna to the receiver or transmitter. We use “coaxial cable” feeder.

SOFTWARE SIMULATIONRun NEC-Win and click ‘New File’ on the tool bar. Enter the details of dipole that has the dimensions (0, -0.05, 0) and (0, +0.05, 0). Run Nec-Vu to check the display of antenna elements. Segment value to 7. Enter frequency value as 1500 MHz both in start and stop with0 step size. Ensure no ground is set. Click Src/Ld and drag and drop the source in middle of the wire. Save the file and then click to RUN Nec. Get different polar and 3D graphs.

DIPOLE ANTENNA IN FREE SPACE USING NEC-WIN

Object:To generate 3D radiation pattern, azimuth pattern plot & elevation pattern plot of a driven element.

Software used:NEC-WIN

Case 1:

3D Radiation Pattern

Case 2:

3D Radiation Pattern

Note: Add desired diagrams or pictures where necessary and other required information for verification of yours lab work

HARDWARE MODELLING

Mount a single dipole antenna on the generator tower. Adjust the dipole length as 5 cm either side of the center. Ensure that the motor enable switch is off. Then switch on the trainer. Run the discovery software. Select the ‘Signal Strength vs. Angle 2D graph’ and switch on the motor enable switch. Get different plots of dipole at different frequencies.Complete the following test:Signal Strength Monitor,Signal Strength vs Frequency,2D Polar Graph

Note: Add the polar plots and all other observations acquired through Hardware antenna.

Practical # 2Effects of Dual Source Dipole Antennas on Wave Propagation; in

comparison with Single Dipole Antenna(Using NEC-Win software)

Objectives To study the propagation of a wave after the effect of two dipole antennas. To further the learning of NEC-Win. To design 2 dipole antennas using NEC-Win plus software

Equipment Required

Dual Source Dipole Antennas By Using Antenna System NEC-Win Plus software

Procedure

Enter the antenna model parameters i.e. length, number of segments, diameter, conductor type and sources/loads.

Enter for both Dipole antennas. Select Polar Plot button to see the AZIMUTH and ELEVATION patterns. Select Add File to add a previously saved single dipole file along with the new

dual dipole patterns for easier comparison.

Single Dipole Antenna Radiations

The Dotted Line represents Single Antenna Radiations

3D Radiation Pattern

CASE 1: Dual Antennas compared with Single Antenna Radiations

Distance between the dual dipole antennas = 10 cm

The Dotted Line represents Single Antenna Radiations

Continuous Line represents Dual Antennas Radiations

3D Radiation Pattern

CASE 2: Dual Antennas compared with Single Antenna Radiations

Distance between the dual dipole antennas = 10 cm

Phase changed at 1 antenna’s source voltage from 0O to 90 O

The Dotted Line represents Single Antenna Radiations

Continuous Line represents Dual Antennas Radiations

3D Radiation Pattern

CASE 3: Dual Antennas compared with Single Antenna Radiations

Distance between the dual dipole antennas = 10 cm

Magnitude changed at 1 antenna’s source voltage from 1 to 10

The Dotted Line represents Single Antenna Radiations

Continuous Line represents Dual Antennas Radiations

3D Radiation Pattern

CASE 4: Dual Antennas compared with Single Antenna Radiations

Distance between the dual dipole antennas = 20 cm

The Dotted Line represents Single Antenna Radiations

Continuous Line represents Dual Antennas Radiations

3D Radiation Pattern

ObservationsWe can generate the radiation patterns of any desired antenna model using NEC-Win software.

The Dual Dipole Antenna Radiations have an adverse effect on each others Radiations. At places they have constructive interference of their generated waves but at other places destructive interference occurs.

The difference between Single and Dual Dipole Antennas with various cases has been recorded and the differences have been observed.

Results The radiation pattern is disturbed at one end or another due to interference of

Waves or Radiations due to Dual Dipole Antennas being in the same vicinity. Changing the Phase of the supplied voltage at the source of one of the two

antennas has a distorting effect. Changing the Magnitude of the supplied voltage at the source of one of the two

antennas has a slight rectifying effect. Increase in distance between the Dual Dipoles causes a drastic effect at the

centre of the Radiations. Major distortion is observed.

Note:Repeat the procedure and construct same antenna on real antenna system, acquire the results and compare them with NEC Win results.

Practical # 8

Ground Reflections Understand that how dipole over both perfect and real ground performs

Practical # 9MONOPOLES

OBJECTIVESTo perform and understand that how a monopole performs over both perfect and real ground.

PROCEDUREConnect the hardware as described in operator’s manual. Load the discovery software as described.

INTRODUCTIONIn this assignment monopole will be investigated.

HARDWARE MODELLINGEnsure that there is no antenna mounted on the generator tower. Identify the ground plane and mount one monopole centrally. Connect RF cable to the monopole and the. Attach the monopole/ground plane to the generator tower. Ensure that the motor enable switch is off and switch on the trainer.Launch signal strength vs. angle 2D polar graph window and switch on the motor enable switch. Acquire a plot.Also ensure that receiver antenna is vertically aligned because monopole is a vertical antenna. So polarization is vertical.Perform Signal strength and polar graph test for monopole.

SOFTWARE SIMULATION. Run Nec-Win and click New File on the toolbar.

Enter the co-ordinates of the two ends of the monopole into the table as (0, 0, 0) and (0, 0, 0.05) meters. Enter the diameter of the wire as 0.004 meters. Enter segment value 7. Click Src/Ld box and place a source at segment 1. Use perfect conductor. Ensure that perfect ground is set and that the frequency is set to 1500 MHz. Save the file. Click on Run Nec button and then examine the azimuth and elevation plots.

Note: Add desired diagrams or pictures where necessary and other required informations for verification of your’s lab work

MONOPOLE ANTENNA USING NEC-WIN

Object:To generate 3D radiation pattern, azimuth pattern plot & elevation pattern plot of a driven element.

Software used:NEC-WIN

Case 1:

3D Radiation Pattern

Case 2:

3D Radiation Pattern

ObservationsThe Monopole Antenna Radiation has an interesting pattern. The perfect ground acts as a

virtual dipole to the actual monopole and hence the complete 360o readings are observed in the elevation pattern instead of just 180 o.

The difference between various patterns at different frequencies is observed.

ResultsTaking readings over a range of frequencies shows drastic changes in the radiation plot

patterns. At lower frequencies the results are much better as compared to higher frequency patterns.Gain at lower frequencies is much less than compared to the gain at higher frequencies.