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					ANTENNAS LABORATORY EXERCISE

You may work in teams of three for this exercise. Please turn in one combined lab report.

In this exercise, your team will experiment with different antennas attached to a laptop
connected to an 802.11B access point.

EQUIPMENT

You will need to the following equipment.

   1.   A laptop with a inSSIDer software installed. Three are available in OMH 246.
   2.   A Buffalo wireless card. This card has an external antenna connector.
   3.   An 802.11B access point. One is available in OMH 246.
   4.   An extension cord to operate the access point.
   5.   A selection of antennas. The following are available in OMH 246:
            a. 6 dBi Collinear Dipole (2x)
            b. 15 dBi Collinear Dipole (1x)
            c. 12 dBi Yagi (2x)
            d. 14 dBi Panel (2x)
            e. 16 dBi Panel (2x)
            f. 24 dBi dish (1x)

SETUP

If it is not raining, setup the access point outside on a stool, away from buildings and cars if
possible. Use the extension cord to power it. You’ll want an unobstructed line-of-sight path to it
for about 50 meters.

If it is raining, set up the access point at the west end of the upstairs hallway. Try to do this at a
time that there aren’t a lot of people in the hallway.

Log on the laptop (you may need a wired network connection to do this the first time – plug in
inside OMH to log on if needed. You can unplug once logged on.)

INSSIDER

InSSIDer is a program that lets you explore various 802.11 signals. Start up inSSIDer (icon on
desktop) and maximize the window.
Change the bottom pane to 2.4GHz channels. Select the Broadcom 802.11g adapter (top-left)
and click on Start (upper right corner). If it show the Intel adapter, you’re using the internal
radio and changing antennas will not work. Make sure it is the Broadcom adapter.

You should see a list on top and graph on bottom. If you haven’t turned on the 802.11B access
point, do so. You should see it (labeled “linksys” and a different shape) on the graph. Un-select
all of the signals on the table (click top-left box) and select only the Linksys access point. You
may look at the signal using the table (RSSI), the 2.4GHz channels display, or the Time Graph.

GETTING ORIENTED

Walk around and confirm that the received signal strength (RSSI) changes as you move closer to
or further from the access point. The Time Graph display can be helpful for this. Plug in an
antenna and confirm that the signal strength is different. Move the antenna around to see how
directionality works. You’ll notice that the signal strength can change rapidly. Reflections and
interference in the environment can cause rapid fluctuations.

DISTANCE-RELATED MEASUREMENTS

Unplug the antenna cable to use the card’s internal antenna. Take RSSI measurements at
around 10, 20, 30, 40, and 50 meters away from the access point. You can use “long” steps to
approximate one meter. You’ll need to let the graph settle at each point and give an
approximate average for the measurement. Graph the RSSI vs. distance.

ANTENNA FRENZY

Set up the laptop 50 meters from the access point. Attach, in turn, each of the antennas
(below) and determine the following for each (use actual measurements, don’t copy from
diagrams!):

   1. Maximum measured gain over the internal antenna.
   2. Approximate 3dB beamwidth (horizontal only). Just guess-timate this – don’t use a
      protractor.
   3. Front/Back ratio in dB.

Report each of these and compare to the advertised values in the diagrams below. Be sure to
describe your experiments and give plenty of observations and commentary. See the lab
assignment expectations below.

EXPECTATIONS FOR LAB ASSIGNMENTS AND REPORTS
The primary purpose of the laboratory exercises is for students to explore wireless signals.
Students who are curious and explore variations on the prescribed lab assignments will get the
most out of the assignment. Students who just follow the directions as quickly as possible will
have minimal learning. All lab reports should be well-formatted and easily readable. The report
should be written in complete paragraphs and sentences, explaining relevant lab setup and
measurements. Lab reports which simply answer the given questions without context will
receive C or lower grades.

      Excellent (A level) lab reports will demonstrate an attitude of exploration. The report
       will include discussion of all results as well as indicate interesting additional questions or
       additional experiments done during the lab time. The report will be well-written and
       easily readable.
      Good (B level) lab reports include all required observations and results as well as
       discussion and interpretation of most all of the results. The report will be well-written.
      Fair (C level) lab reports will include required results but little more.
      Poor (D or E level) reports will include only a subset of required results.



GAIN DIAGRAMS FOR ANTENNAS


                   Hyperlink HGV2406U 6dBi Collinear Dipole
Hyperlink HG2415U-PRO 15dBi Collinear Dipole
Hyperlink HG2412Y 12dBi Yagi




                         \
Hyperlink HG2414P 14dBi Reflector Panel




 Hyperlink 2416P 16dBi Reflector Panel
          Hyperlink HG2424g 24dBi Parabolic Dish

(Diagrams assume mounted with long side of dish horizontal)

				
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