Given the measurements of the SWR on channel 1 vs he measurement of the the SWR on channel 40, the antenna might need to be shortened or lengthened. The following table summarizes all the possible cases.
SWR Channel 1 | SWR Channel 40 | Antenna |
|---|---|---|
lower than 40 | higher than 1 | too long, needs shortening |
higher than 40 | lower than 1 | too short, needs lengthening |
equal to 40 | equal to 1 | right size |