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Preparing the Can Antenna

It’s time to get the can ready to be converted into a directional antenna. You can do this in two
steps: preparation and cleaning.
Step 1: Preparing the Can Opening
The coffee can you purchased probably has a plastic cover on the top and a metal cover protecting the coffee freshness. Remove the plastic lid and put it aside; you will use it later. You will also want to make sure that the can itself is intact with no indentations. Most cans will have ridges around the circumference of the can which are okay; you just want to make sure that it has not been dropped or mishandled. These indentations or dents can affect the efficiency of the can. The coffee can will be sealed in one of two ways. With many of the older coffee cans, you needed to open the can with a can opener and discard the removed lid. If this is the coffee can you have, make sure that you grind down or file the inside edge of the can so that it is smooth. If it’s a newer can, it will have a thick tin foil covering with a ring to pull the cover off. Simply
remove the cover and discard it.
Step 2: Cleaning the Can
While having coffee grounds in the antenna will not affect its operation much, it sure can make
a mess of things, so make sure that you clean the can out well. Also make sure that you clean
the opening of any foreign objects, such as glue, pieces of the original tin or tin foil cover. Where to Drill We will be using a copper wedge as the driven element or radiator. The location and length of this element is extremely important. Although we will not be going too deep into the math here, it’s important to understand where this driven element is to be installed. The rule of thumb is that the driven element should be at one quarter of the “closed-space wavelength” from the inside edge of the can when the connector is installed. The difficulty here is that the closed-space wavelength will vary based on can and radiator dimensions. On our can, with an inner diameter of 100 mm, this offset was slightly more than 1 inch or 27 mm. Once you have this measurement, it is time to prepare the hole in the can where the

N-Connector is to be installed.