Building the Paperclip Antenna

Building the antenna is a seven-step process, as follows:

1. Prepare the antenna elements

2. Get the mounting platform ready

3. Create the driving element or dipole

4. Prepare the pigtail

5. Attach the pigtail to your new antenna

6. Secure the pigtail

7. Insert the last few elements into the antenna

Figure 2-13 shows the basic components and how they come together. Note that the rounded paperclip (piece 3) is the actual driven element of the antenna. That is, it’s the wire getting the radio signal from the wireless card. The other paperclips (pieces 1, 2, and 4) shape the beam to make it more directional.

Step 1: Preparing Your Wire Prongs

Each radio frequency has a specific wavelength.To function as an antenna, the dipole loop has to be half the length of that wavelength.

Take your needle-nosed pliers and carefully straighten four large paper clips. Cut them to the lengths indicated in Table 2-1.

Step 2: Preparing Your Antenna Platform

Carefully mark on the wooden platform the five places where the wires of your antenna will be passing through. See Figure 2-14 for hole spacing for the paperclips. This design is optimally tuned for reception on Wi-Fi Channel 6 (the approximate middle of the frequency band). It will also work on the other Wi-Fi channels. But if you really want to get peak frequencies, paperclip length and distance apart from each other will differ for each channel. See the section How Are Dipole Dimensions Calculated later in this chapter.

Using your hand drill, drill the five holes using a drill bit slightly smaller than the paperclip wires.

As an alternative, you can punch the holes by laying the platform flat on a table surface, and gently tapping a thin wire brad through the wood with a hammer. However, you can easily split the wood this way (especially on platform materials like an ice cream spoon or a popsicle stick).

Patience is a virtue when mounting the paperclips. Work the paperclip into the material slowly with a gentle twisting and pressing force and everything should be fine.

Step 3: Creating Your Dipole

Take the longest wire (the one that is 4.52 inches long) and form it to match the template in Figure 2-15. This template is printed to scale. After bending the paperclip as described here, lay it on top of this diagram to ensure the correct dimensions Take your needle-nosed pliers and make a line on the nose at the point where it is 0.16 inches (4 mm) thick. Clamp the largest wire with the pliers and make a bend that starts 1.3 inches from one end,. Slowly wrap the paper clip wire around the needle nose, creating a fishhook that is 0.16 inches wide (4 mm).

Carefully press the longest end of the fishhook through the first appropriate hole on your platform.Work the wire into the hole, until the second end comes up to its appropriate hole. Ease that second wire through so that its end just pokes through on the other side of the platform.

Take the long protruding end of the wire and carefully create the second bent end, bringing the two ends extremely close together (about 1 mm or 0.04 inches), and create your radiating dipole. (See Figure 2-16.)

Step 4: Preparing the Pigtail for Attachment

Take your wire cutter and simply snip off the large standard N connector on the end of the pigtail. This is where a factory-built antenna would be connected to the pigtail or jumper cable (as described in Chapter 1). Since we are soldering the antenna directly to the pigtail, the connector is not needed.

Be careful not to snip off the smaller end of the pigtail, which needs to be attached to your laptop wireless card. Strip off about three-fourths of the outer insulating jacket and the inner dielectric insulation surrounding the core conductor.

You will need about 1/4 inch of the central core free, to create a soldered connection to one end of the dipole. And you will twist about 3/4 inch of the outer shield into a tight coil in order to solder it to the other end of the dipole. (See Figure 2-17.)

Step 5: Soldering the Pigtail to the Dipole

Put the bent paperclip dipole in a stable grip, either in a small tabletop vice, or in a pair of vise grips. Don’t touch the paperclip or the solder iron while you work on this, both will be very hot. Be sure to wear eye protection because splattering solder can cause serious eye damage. Also, the solder resin causes some fumes that can damage your lungs, so make sure your workspace is ventilated to avoid any unhealthy buildup of vapors.

Carefully solder the core conductor and the shield to either end of the bent dipole radiator (as shown in Figures 2-18 and 2-19). Both sides of the paperclip need to be soldered to the pigtail, but they must not touch each other or the antenna will be useless. When you choose a mounting platform, plan ahead to prevent the ends from touching.