We have found this alternate procedure usually solves 40m SWR issues for most of our customers:
Before starting, mark the starting locations of the tubes and trap covers so that you can restore the lengths if necessary.
- Shorten the tubing adjustment between the 10m and 15m traps.
- Shorten the tubing adjustment between the 15m and 20m traps.
- Re-calibrate the 15m and 20m traps to offset the changes
- Return the resonant points on those bands back to where they were.
Remember, it should NEVER be necessary to cut any of the tubes on a BTV antenna in an effort to tune it.