I think the correct answers are there. I have tried a few. I have a 40 meter whip I adjust with set screws, and a chart to cut it for that band. For CB, depending on the antenna, adjust the length according to an SWR meter between CHs 40 and 1 and get it as low as possible, without cutting it. If it is a steel whip, remove it and cut it from the bottom as suggested (.25 inch at a time) and re-measure between snips. My favorite antennas are fiberglass mirror mounted Francis brand 4 foot antennas, which seem to need no tuning. ( My Volvo mirrors are grounded. ) The Cobra 29 LTD and amp seem to have no trouble, around 1.5 to 1, or better.