All CB antennas are tunable. Antennas that have an easy, often mechanical, tuning device are referred to as a "tunable antenna". Accordingly, lots of people think the other antennas are not tunable and so they make no attempt to have the antenna tuned. This is a critical mistake.

Wire-wound antennas without mechanical tuners, that test electrically long (higher SWR on ch 40), can be tuned by removing wire from the top. Remove the antenna cap, remove one wrap of wire and cut it off. Recheck the SWR again. As long as the SWR is higher on channel 40 continue to cut. Do not cut more than one wrap at a time. If SWR testing indicates the antenna is electrically short (higher SWR on ch 1), the coils at the top of the antenna can be separated and spaced further apart or accessories that increase the physical length of the antennas (springs, quick disconnects) can be added.

Solid fiberglass antennas (straight or helical wire impregnated in fiberglass resins) that are electrically too long (higher SWR on ch 40) can be cut shorter with a hacksaw or grinder. Cut only 1/4 of on inch at the most at one time. If the SWR test on one of these antennas indicates that it is electrically short (higher SWR on ch 1), the addition of a spring or quick disconnect (or both) is the only way to correct for the short condition.

Base loaded antennas with wire whips have a set screw (or two) just below the area that the whip is inserted into the loading coil. By loosening up the set screw(s) you are able to slide the whip up or down as required. If the SWR is higher on ch 40 slide the whip down, If the SWR is higher on ch 1 raise the whip.

Setting the antenna SWR with an amplifier can get involved. The antenna SWR is calibrated at the back of the amplifier with the amplifier in line and turned off. Once the antenna is properly tuned the meter is removed and re-installed at the radio with the amplifier in line. The antenna SWR level is then measured with the amp off and then with the amplifier switched on. The SWR level must be at an acceptable level at the radio under all conditions. The conditions are with the amp off on channel 40 and 1 and with the amp turned on, on all power levels of the amplifier on channel 1 and 40. Most shops don't check the SWR match at the radio with the amplifier turned on. This is a critical mistake. With these steps added the SWR calibration can turn into a multi hour event at times.