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SUMMARY OF THE DAYS ACTIVITIES
Monday, 13th February, 2006
This first day of the second week got off to a slow start, or was it fast??? Never mind... it is probably because I was among the ones with a hang-over from the weekend that made it seem a slow start.... at least for myself and the many who came in late today....
But soon as it got started, things heated up because the first topic covered; Basic Antenna Theory by Prof. Struzak was not one to be auditted in the 'sleeping mode'... :-) One had to wake up quickly to the technical, semi-imaginary things being talked about.. This does not mean it was difficult to understand, for when it came to the application part, where Rob took us through the 'what and how' in the design of DIY WiFi? Antennas the whole topic came alive like fire. The 'why' was answered almost completely by Prof's presentation. Brilliant presentations, as usual!
Following this closely was the labs, lead by Rob and Fonda, which practicalised everything we have been listening to in the day. And this was, of course, the most participatory and exciting part, as we all turned into techinicians, cutting, filing, drilling and screwing everywhere, measuring and redoing the whole show again. In making the can antenna, we measured, cut, drilled, soldered and cut again. But why cut the antenna wire 3cm long and not 5m?. Why drill 6.2 cm from the base of the can and not 10cm or at the middle? What is the relationship between the antenna length and the frequency? Most of these questions were answered understandably in the lab. Very very exciting.... After reading the above, you could quit. And I hope you've grasped what we did today. But if not and if you yearn for the real details here they are:
The topics covered today are:
\\(this was in two sessions separated by a coffee break.)
\\[ DIY stands for Do It Yourself .... And I DID IT!!!..:-) ]
\\(i.e. the real DIY . Also in two sessions with coffee break between)
Prof. Struzak's lecture was precise and to the point. The purpose was 'to refresh the memory of particpants on the basic concepts of antenna physics that is required for a better understanding of the design and operation of microwave links and networks' (paraphrased). This is exactly what the Prof did, with a clear lecture covering basic types of antenna, theory of radiation patterns, gain and polarisation, equivalent circuits, radiaition efficiency and smart antennas. It covered intended and unintended radiation. Prof. Struzak explained that whether an antenna is transmitting or receiving it has a set of charateristics- gain, beamwidth, efficiency, polarisation, impedance, etc -which are independent of it's use and the same basic theory can be applied. In the context of wireless networking an antenna serves as an interface between the em generator and receiver. The antenna transforms the em wave from the transmitter(generator) so it can be propagated through the air. A receiver does just the opposite and the two have equivalent power circuits. He stated that the impedance and radiation patterns of an antenna are the same when it radiates and when it receives a signal. The antenna could be directional or omni-directional depending on it's radiation pattern.
A simplified equation relating the power and gain of an antenna is
On the DIY for WiFi? antennas, Rob displayed different types of antenna that can be made at home from simply tools and at very minimal cost. The simplest of these was the spider antenna.Other antenna shown included biquad antenna (http://trevormarshall.com/biquad.htm ), slotted waveguide (http://trevormarshall.com/waveguides.htm), parabolic antennas, and the can (or pringles can) antenna. We then proceeded to build the can antennas. The guidelines we followed are outlined clearly in the Wireless Handbook (http://wireless.ictp.it/handbook/download.html). Good antennae gave frequencies of between 2.4031GHz and 2.48GHz when measured with spectrum analyser.
The exciting LABs? did not end early- as usual- for, people returned after dinner and continued to measure, cut, file, drill and screw out till late in the night. So when did they end?... TRULY, I DON'T KNOW!!! ..:-)
By: Walter N. Kaba, Ghana