Understanding antenna specifications.

So many different antennas, which one is the best? Just what should you look for in an antenna?

For single band use, you need a minimum of 450Khz. For each additional band, add another 440KHz.
For dual band UK CBs, covering UK and EU bands, you will need just over 1MHz as there is a space between the bands.

Decibels (dB) are a relative measurement, showing performance compared to some standard. Unless they tell you what they compared it to, then the figure is meaningless.

This is the amount of gain when compared to a dipole. Higher figures are better, but you can only compare if both figures are in dBd or you can convert between the two units used.

Another method of showing gain, by comparing to an isotropic radiator. Higher figures are better, but you can only compare if both figures are in dBi or you can convert between the two units used.

For American and European use, the antenna should cover from below 26.96MHz to above 27.41MHz.
For dual band UK use, the antenna should cover from below 26.96MHz to at least 28MHz.

See dB Gain, dBd gain and dBi gain (above).

The antenna impedance should match the impedance of the radio, which should be 50 Ohms.

A greater physical length is generally better, the antenna will work better. If you have limited space, a smaller physical size may be more practical.
Some may quote electrical length, don't be too impressed by large electrical length figures.

For CB use, the antenna will usually need to be vertically polarized. Most antennas will be vertical, some will work vertical and horizontal.

This only need be the amount of power you use, plus a little extra so it is not running at the limit. For legal For UK CB use, this only need be 10 Watts.

A lower is figure is better, although it is not critical. A typical figure is 1:1.3 although 1:1.5 is fine.

Naturally, higher figures should be better, although it will depend upon what they consider "survival" - will the antenna still be usable?