The SWR Meter.

This is used to tune the antenna to the frequencies used.

Tuning the antenna is important, as a mistuned antenna will not work efficiently, may cause interference, and may damage the radio.
Although it is important to tune the antenna, you do not need to get a "perfect" reading. Lower is usually better, but a reading of 1.5 or below is fine.
Always disconnect the meter once the antenna is tuned, and only connect it when checking the antenna.

There are several different models of SWR meter, with different features. Some meters may include a power meter and a field strength meter.
Usually, a basic SWR meter is all that is needed.

This feature measures the amount of power leaving the CB radio. As the power from a UK CB radio is 4Watts, this feature is only used if you suspect a faulty radio. To get an accurate power reading, a Dummy Load should be connected in place of the antenna.

This feature measures the amount of signal actually leaving the antenna. A small antenna is connected to the meter to receive the signal, which is then measured and the level displayed on the meter.
This can be useful for checking if an antenna is putting out more signal in one direction, if one antenna is working better than another, etc.
This feature may look impressive and sell meters, but it is rarely used by CBers.


Some meters combine many different functions, and use two or three meters to display the readings. Such equipment is not really necessary for general CB use, it is more appropriate for someone who tests and tunes CB radios and antennas.
The meter shown on the right is a Reace RC-1000. This measures SWR, power, field strength, modulation and FM deviation.