Continue with this process until ch 40 & ch 1 are relatively the same. If there was no fluctuation adjust the rod up or if threaded turn the device counter-clockwise. If the SWR fluctuates a ground problem exists and must be corrected before proceeding. Move the coax around bending it, again watching for SWR fluctuation. Do not touch or even get close to the antenna. Touch the antenna bracket while keyed and watch for SWR fluctuation. If SWR testing indicates the antenna is electrically short (higher SWR on ch 1), test for a ground problem. As long as the SWR is higher on channel 40 continue to adjust the rod down or if threaded turn the device clockwise. Put the cap back on and recheck the SWR again on ch 40 & ch 1. Remove the antenna cap, and adjust the rod down or if threaded turn the device clockwise. Wire-wound antennas (with mechanical tuners), that test electrically long (higher SWR on ch 40), can be tuned by adjusting the mechanical device at the top of the antenna. If ch 40 is higher cut 1/8 inch of wire, put the cap back on and check the SWR on ch 40 & ch 1. The goal is to reverse the situation so that ch 40 has a higher SWR than ch 1. If there was no fluctuation bend the end of the wire straight up the fiberglass shaft and lap it over the very top of the fiberglass shaft. As long as the SWR is higher on channel 40 continue to cut.
Remove the antenna cap, remove one wrap of wire and cut it off. Wire-wound antennas (without mechanical tuners), that test electrically long (higher SWR on ch 40), can be tuned by removing wire from the top. Accordingly, lots of people think the other antennas are not tunable and so they make no attempt to have the antenna tuned. Antennas that have an easy, often mechanical, tuning device are referred to as a "tunable antenna".