Make your own antenna - The Dipole.

The Dipole is a very versatile antenna, with no set polarization, which can be easily mounted and even modified to create other small space antennas. A Dipole consists of two conductors of equal lengths. These conductors may be made from tubing, wire, or even from the coaxial cable itself.

As the diagram on the right shows, one conductor connects to the centre - this is the driven element. The other conductor is connected to the braid, or screen wire of the coax. If the dipole is used vertically, the driven element should point upwards.

The impedance of a dipole in free space is about 70 Ohms, which will give a standing wave ratio of 1.4:1 on a CB system. This impedance and SWR will change as the antenna is moved closer to or further away from the ground.

Polarization.
This antenna can be mounted either vertically or horizontally although, for CB use, vertical is recommended.

Directivity.
If the dipole is mounted vertically, it will exhibit very little directivity, and should radiate fairly equally in all directions. However, if it is mounted horizontally, it will be directional with most signal from the side, and very little signal from the ends.

Length.

Type / diameter: Band: Length: 1mm wire 1mm wire 1mm wire 1cm tubing 1cm tubing 1cm tubing UK CEPT Both UK CEPT Both 524.5cm 536.3cm 530.6cm 517cm 528.6cm 523cm

At CB frequencies, a half wave is about 5.45 Metres (about 17.9 feet). The exact length you require will depend upon which band you wish to tune it for and the material used for the antenna.
Shown on the right are approximate sizes, the exact length may vary with the type of wire or tubing used. The shown lengths are for the complete dipole - top and bottom parts are each half of that size. If you make the dipole slightly long, you can cut it down to tune it.

Construction.
The easiest option is probably to make the antenna from the coax. To do this, you will need to strip away the outer casing of the coax to half the length of the complete dipole - making the braid visible. You then push some of the braiding apart near the part where the insulation is still on, and pull the inner wire (with it's insulation on) through that hole. Insulate the end of the coax, so water does not get in, fit a coax connector on the other end of the coax, and it is ready to mount.

Another option is to cut two lengths of wire, each half the dipole length. You then strip the insulation from the end of some coax, and solder these wires to the end. The connections should be well insulated, so that water does not get in.

If you are feeling adventurous, you could make the dipole from tubing. As with the wire dipole, you will need two lengths, each half the dipole length. You could make each half out of two pieces, which slot inside each other. This way, the antenna length can be adjustable.
You will need something as a base, which the tubing and coax will go into to make the connections. It will need to be non-conductive (possibly plastic) and you will need some way of fixing it to a wall, gutter, etc.

When cutting lengths, remember to be cautious - the wire dipole should be cut slightly longer than you expect, as you could trim it when tuning. With the coax dipole, it may be possible to strip back a bit further to lengthen the dipole when tuning. The tubing is best done with sections as suggested, and made slightly long so that it can be tuned by sliding the sections inside each other.

Mounting.
Wire dipoles can be dangled from objects, tied to bamboo type sticks, mounted on walls, etc. It should be remembered that nearby objects affect the signal, so open space is best.
Tubing types can be mounted from a wall or pole.

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