Occasionally the tuning process will indicate that you need to further increase/decrease the length of your antenna, but you've come to the limit of how far the antenna will adjust in a certain direction. What to do now?
If the antenna needs further shortening:
If your antenna needs to be further shortened, you can usually do this by either trimming the stainless steel whip with pliers OR by removing the tuning screw from the tip of the antenna. These options will often allow you to shorten the antenna enough to finish tuning. In extreme cases, you can also trim the wire windings on a fiberglass antenna after removing the tuning screw to shorten it further.
WARNING! If cutting an antenna, make sure you do it INCREMENTALLY in very small sections, taking readings in between cuts. If you cut off too much, there's no going back! Make sure the pre-cutting average of your two SWR readings on Channel 1 and 40 is acceptable, as this will be close to the final overall reading when you've finished. If this average is significantly above 2.0, you'll want to reconsider your mounting location and re-tune the antenna. Please see our article on how poor mounting locations can cause high SWR regardless of how you tune your antenna.
If the antenna needs further lengthening:
Often adding a spring or a quick disconnect to an antenna can help if the antenna needs to be lengthened. While it doesn't change the electrical length of the antenna, the increased height can often help with this problem.
If you still can't get the antenna short or long enough:
If you are still unable to get the antenna at the perfect length to have matching SWR on channels 1 and 40, you should consider your SWR readings. If SWR readings on Channels 1 and 40 are both below 2.0, you can safely operate your radio with acceptable performance and may choose to do this instead of pouring more energy into getting “perfect” SWR across the board. However, if one or both of Channel 1 and 40 readings are significantly above 2.0, you may want to consider moving your antenna location for improved performance (please see performance hampering mounting locations) or even try a different antenna, which might tune up better given your vehicle's construction.
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