My WARAU Project

1. 802.11 WiFi Adapter Reception Amplification unit Research Project Fabius Watson

2. Project Goal Overall Goal Construct a device that increases wireless signal gain by a minimum of 10 dBi. Provide the device with simple functionality. Incorporate a swivel mount for adjustability.

3. Parabollic Dish Approach Most WiFi Adapters are built for omnidirectional functionality. Most users only connect to a single access point (EX: linksys) at a time. The Devices omnidirectional functionality limits maximum gain. A Parabollic Dish would reflect all captured signal toward the focal point of the dish, at which the adapter’s antenna would be located, maximizing signal gain from a single access point.

4. Materials External USB 802.11b/g/n Wireless LAN Adapter USB 2.0 Extension Cable, 10 ft Camera Tripod Plywood Duct Tape Aluminum Foil Poster Board

5. What is a Parabolic Dish? A parabolic reflector (or dish or mirror) is a reflective device used to collect or project energy such as light, sound, or radio waves. Its shape is that of a circular paraboloid, that is, the surface generated by a parabola revolving around its axis. The parabolic reflector transforms an incoming plane wave traveling along the axis into a spherical wave converging toward the focus. Conversely, a spherical wave generated by a point source placed in the focus is transformed into a plane wave propagating as a collimated beam along the axis. (Source A)

6. How Does a Parabolic Dish Work? When EM waves arrive on parallel paths from a distance source and are reflected by a mirror or flat surface, the angle of the path leaving (angle of reflection) is the same as the angle of the path arriving (angle of incidence). If the mirror is a flat surface, the two rays of light leave in parallel paths; however, if the mirror is curved, two parallel incident rays leave at different angles. If the curve is parabolic (y = ax^2) then all the reflected rays meet at one point. A dish is a parabola of rotation, a parabolic curve rotated around an axis which passes through the focus and the center of the curve. (Source B)

7. Parabola with focus and arbitrary lines (Source A)

8. Aperture The aperture of an antenna is the area that captures energy from a passing radio wave. For a dish antenna, the aperture A would be the area of the reflector as seen by a passing radio wave: A =πr2 Where r is the radius, half of the dish’s diameter. (Source B)

9. Gain The gain of an antenna in a given direction is the amount of energy radiated that In that direction compared to the energy an isotropic antenna would radiate in the same direction when driven with the same input power. An antenna with a large aperture has more gain than a smaller one; just as it captures more energy from a passing radio wave, it also radiates more energy direction. 𝐺𝑑𝑏𝑖=10log10(𝜂4𝜋𝜆2𝐴) 𝜂, the apertures’ efficiency, is the ratio of power received to power arriving. (Source B)

10. Focal Length In order to determine the focal length, you must measure the diameter D and the depth d. The focal length is calculated as: 𝑓=𝐷216𝑑 (Source B)

11. Construction - Parabollic Dish In order to build my own parabolic dish I loosely followed a guide found at www.instructables.com, making slight improvises in terms of materials.

12. NOTE TO THE AUDIENCE All Slides Proceeding This Slide Are Completely Impromptu

13. Dish Fail However, My Dish Construction Failed. =( It was too heavy due to foil, glue, and duct tape It’s weight caused a degradation in its stability, giving it a flimsy form

14. Testing the Dish Anyway Despite, my dish failing, I decided to test the dish anyways. I was able to crudely test for an increase in gain using my Ipod Touch and a tool called WiFiFoFum. Calculating a focal length of 7.8 inches, and strategically placing my Ipod Touch at approximately this length at the center of the dish, I was able to get a maximum of a 20 dBi increase in gain

15. Conclusion Although my design was plausible in theory, it was flawed when physically applied. Applied science is much more frustrating than Pure science. Things Fail.

16. Fail Cont… Another problem that I ran into is getting the wireless adapter to register on my computer. The Wireless Adpater I attempted to use contained a Ralink rt3070 chipset. Ralink fails at chipsets. The rt3070 chipset is the same exact chipset as the rt2860 with minor bug fixes. I had to reconfigure the driver for the rt2860 so that it would register as the rt3070.

17. Driver Wont Install

18. Finally After 2 hours of CLI torture, I managed to get the driver to install.

19. However… The Physical Adapter would not function at all. After hitting up freenode/#sabayon for some help, I was able to determine the cause of the problem. The USB Adapter was not receiving enough power to function properly due to: The 1.82 m USB extension Cable (power is lost over the distance) Front Panel USB port. A Root port is necessary for maximum power. So after moving the USB to a root port & removing the USB adapter I was able to get the adapter to function properly. Just one minor issue…

20. More Fail*cries* I need the adapter to work with the USB extension cable. Without the Extension cable, the adapter will never reach the dish

21. Waveguide Approach Speaking of the dish, I decided to scrap the dish idea, as it utterly failed. I decided to instead construct a model based on an Waveguide Antenna.

22. Cantenna I recalled back to when I began this project and remembered a picture I had seen of similar projects. I turned out to be called a Cantenna It involved the usage of a pringles can to reflect the wireless signal, and looked fairly simple to construct. And so I decided I had nothing to lose and proclaimed (to myself) my refusal to ReInvent the wheel. i buy tehpringles

23. Pringle Fail While the Dish, though crappy, boasted a max 20 dBi increase, the Pringles can, though cool looking and inventive, boasted a min 15 dBi decrease. Turns out the inner coating of the pringles can, contrary to my previous belief, is NOT mettallic. Waveguide functionality will NOT work. However if I had taken a Yagi-Uda approach (Microwave Resonance), It probably would have increased my gain by at least 10 dBi. DO NOT believe everything you read on the internet.

24. FMJC: Full Metal Jacket Cantenna Well, If Metal is the problem, I’ll simply a Full Metal Can, rather than a cardboard pringles can. I’m going to stick with the Cantenna design as it is documented as having worked fairly well on several different occasions.

25. 𝐶𝑎𝑛 𝑊𝑖𝑛!2 The Tin Can Cantenna works fairly well in that I achieve a 15 dBi increase. The Downside of this is that the wireless adapter that I originally intended to use has still failed to gain enough power to constantly function correctly. (I did manage to get it to register for a brief moment, but soon after it died.) And the one I’ve been using for testing (Yes, I dumped my Ipod touch) is half broken (What a surprise! It sports a Ralink chipset as well!.) Also the can is small, crude, ugly, and not what I was going for.

26. Now What? I’ve run out of time, and hereby proclaim this project:

27. What did I dBi? (Gain, get it?) This project wasn’t a complete lost, I learned as much doing this project as I did I most of my other classes. I learned a ton about waves, antennae, parabolas, etc. That I didn’t know before, and probably would never have learned unless I did attempt this project or a project similar. I learned to modify & compile drivers in Linux using C? I learned that engineering consists of more than just math and physics. It also consists of trying, failing, and trying again. I learned that Cantennas are completely Illegal. That’s right, after completing this project, I discovered that what I wa doing violated FCC guidelines any way, and carried a hefty fine. Also, if it only took about 10,000 tries for Edison to perfect his light bulb, he must have been a genius.

28. Not Done Yet Despite the Law I plan to continue my research on Wireless Adapter Reception Amplification Units I may attempt to construct a model using a Satellite TV dish and a BiQuad antenna. This model has reported achieving a max 30 dBi increase. I’m also thinking about an Umbrella Frame with a Wire Mesh. Bigger aperture, more gain, remember? I also plan on experimenting with Bluetooth and GPRS

29. Works Cited (Source A) Chambers, Robert. "Parabolic Reflector." Wikipedia, the Free Encyclopedia. Web. 16 July 2010. <http://en.wikipedia.org/wiki/Parabolic_reflector>. (Source B) "Web Site Of: W1GHZ (n1bwt)." Welcome to QSL.NET :: Web Services for Ham Radio Operators. Web. 16 July 2010. <http://www.qsl.net/n1bwt/>.

30. WiFi Is Sexy