Antenna Construction

University of Alberta observatory domes

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3 Element Yagi
Dimension Table

"Thank you so much for visiting our class on Friday! The kids loved it...they thought it was pretty cool to meet a "real" Astronomer! Thanks again, Janine"

Updated March 14, 2011

How to Build Your Antenna

We are recommending that you build or use a Yagi antenna. This will give you the best gain (detection) of the signal. What will determine that you can use this type of antenna is if you can place an antenna on the roof of your school or if you have enough room to put it up in your classroom. Go to Yagi Antenna Construction if you can use this type.

If neither of these solutions are possible, then you may be able to use a folded dipole antenna hung inside your class or outside your classroom window. Please note that folded dipoles have not been shown to work yet in our tests. Another option is for Sky Scan to provide you with data from other schools or from the Sky Scan observatories for students to analyze.

Yagi Antenna Construction

There are three parts to this antenna, the boom, the elements, and the mount. One piece is needed for the boom, several for the elements and mount.

The boom works best if it is as light as possible yet strong enough to provide rigidity. Since it will be exposed to rain it can be galvanized steel, such as the top rail used in chain link fences, aluminum or weather treated wood. While aluminum is light and ideal for the task, it tends to be more expensive and more difficult to find. On this website we have instructions for two different ways of building Yagi antennas. Both methods can be used for the 3 or the 6 element design we are recommending. One is made entirely of wood, the other is a combination of pieces of plywood and pipe. 

We recommend that schools use or build a  3 element Yagi, the instructions for which can be found at this link. Also, please contact us if you have any questions about building your antenna. We can supply you with a pre-built antenna that will save you the trouble, if not the learning, involved in building your very own.

If your school has a construction class, many of the tools and materials required for constructing different antenna designs may be found there, along with the help you may need to build the antenna and mounts.

Once you have determined the frequency you will be observing at, calculate the minimum total length of the boom by using the Dimension Table. Be sure to look up the correct frequency along the left hand side of the page. You need to add the spacing between each element together to get the minimum total length figure. The boom you use will need to be at least that long.

Measure the spacing between the elements on the boom and mark each spot using liquid paper or some other permanent marker. You should also mark which elements go where on the boom since the spacing is different for each element.
As the illustration shows, the boom holds the elements of the antenna at the proper distance from one another. The metal elements can be held in position by a variety of methods. We describe two methods: one using all wood construction in the 3 Element Yagi design, the other uses a combination of a metal boom and wooden adjusting blocks described in the 6 Element Yagi design. 
 

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We gratefully acknowledge the financial support of the 

Edmonton Centre of the Royal Astronomical Society of Canada, Department of Physics (University of Alberta)

and the

Natural Sciences and Engineering Research Council of Canada

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