The Dipole Antenna is just about the simplest antenna . The dipole is a half-wave antenna that consist of two opposing radiating elements. It's made up of two quarter -wavelength poles that are connected to each other and fed in the middle by transmission line. A standard dipole is open on each end, but it can also be folded over on itself. The Figure below shown is a folded dipole with paperclip.
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| A Folded Dipole antenna made out paperclips |
Simple folded dipole made with steel paperclips. Each arm of the dipole is 31 mm in length, or 1/4 of a wavelength or Wi-Fi channel 6. The center conductor is soldered to the right arm, while the shield is soldered to the left arm. It doesn't matter to which side you solder.
The dipole antenna is unique in that it can be mounted vertically or horizontally. When standing vertically, the dipole antenna is omnidirectional. When horizontal, this antenna will radiate outward in two directions off the sides (and slightly upwards), like turning a donut on its edge.
This paperclip antenna can produce a gain of up to 9 dBi.
Prepare the items you will need to build the antenna :
- Four large paperclips (the largest has to be at least 11.49 cm (4.52 inches) when straightened
- A Flat wooden spoon , the kind that comes with ice cream cups -- or some other suitable platform for supporting your antenna prongs
- Wi-Fi pigtail cable connected to your laptop NIC (PCMCIA wireless card with an external connector)
- Solder iron and solder. An iron in the 15W to 30W range will work fine. Thin rosin core solder (0.75 mm is good size) is preferred for electronic work because acid core solder will corrode components.
- Small bottle or tube or craft glue (virtually any kind will do)
- Small wire cutters
- Needle-nosed pliers
- A ruler that marks tenths of an inch (such as a drafting ruler from a craft store) or a metric ruler with markings for millimeters
- A pen for marking hole locations
- Eye protection for cutting wires and soldering
- A pair of vise grips or (even better) a small tabletop vise (the kind used for making fishing flies) for holding your antenna securely while working on it.
- A drill with a bit slightly smaller than diameter of the paperclips or else a thin wire brad and a light hammer for tapping it through the wood
You will have more success in your paperclip antenna project if you are working with a good wireless card. Wireless cards can come with or without built-in external connectors.
It is possible to access the internal connectors of wireless cards (NICs) that don't have such external jacks--but doing that is its own separate bit of technical wizardry that involves "cracking the case" of the NIC to get at its connectors.
However, the mind boggles at all the many possible materials that can be used. These antennas have been made with medical tongue depressors, floppy diskettes, and small cardboard tubes. We used a jumbo-sized craft stick, also known as a popsicle stick. Plastic cards don't work well , because they are too thin. They don't support the prongs well (without mounds of glue) and so the prongs tend to flop over and even touch.
You can glue a wooden clothespin to platform you select, so that the antenna can be easily clipped on a stable mount, like the side of your laptop screen.
Building The Paperclip Antenna
There are seven step process for building the Paperclip Antenna :
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
The rounded paperclip (piece 3) is the actual driven element of the antenna. It is the wire getting the radio signal from the wireless card. The other paperclips (piece 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 picture below for hole spacing for the paperclips.
The design is optimally tined 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.
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 as Figure below . This template is printed to scale. After bending the paperclip as described here, lay it on top o 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 ( 4mm ) 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 ( 4mm).
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 as figure below.
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 . Since we 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 as seen at figure below.
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 the bent dipole radiator as shown in Figure below,
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| Soldering the pigtail center conductor the paperclip |
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| Soldering the pigtail shield to the other side of paperclip |
Both sides of the paperclip need to be soldered to 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.
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