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.

Table 3-1 shows some of these dimensions for channels 1, 6, and 11 using two different types of radiators. A narrow-band pole, and wideband wedge. The wideband wedge needs to be built only for channel 6 because it operates well across the entire Wi-Fi range of frequencies.

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.

Remember to measure this carefully, because a mistake means you need to buy and use more coffee.

As mentioned earlier, measuring the distance to the opening is critical to the operation and efficiency of the antenna. The old saying “measure twice and cut once” is also true here. But instead, remember to “measure twice and drill once.” Measure the correct distance from the top of the ridge at the bottom of the can, as shown in Figure 3-6.

There are several ways to get the hole for the N-Connector the right size. The method you use is up to you. The final hole should be the diameter of the N-Connector stem. In one method you can drill a small hole and work your way up to the desired hole size. Another method, which is more time-consuming, is to use a nail to make the initial hole and

use a file or cutter to enlarge the hole. If you use this method, make sure you don’t dent the side of the can. The can should stay completely round. We drilled the hole using a 3/4 inch drill bit, as shown in Figure 3-7.

There are different types of N-Connectors that you can use for this project. The type does not really matter. As you can see from Figure 3-8, our connector had four screw holes (one at each corner). The best way to ensure that the connector is installed properly is to insert it into the opening you created in Step 2, line it up, and mark out the holes for the four mounting screws. Once this is done, you can drill them with a drill of the same diameter as the mounting screws.

The final step in preparing the N-Connector hole is cleaning it. Using a small file, make sure that there are no edges or burrs around the openings. This will ensure a tight fit when the connector is inserted and connected to the coffee can.