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Tuning the Vertical Antenna System
The actual impedance of the 40 meter antenna is affected by local conditions, including proximity
to structures, other antennas, number of radials, or personal preference for the mounting location. It
may be necessary to adjust the top element section slightly longer or shorter when tuning the
antenna to best SWR.
When the antenna elements are completely assembled and mated to the base section, the overall
length measured from the top of the antenna to the bottom of the base section should be 299” (24
Feet, 11 inches)
prior to tuning
. This allows you to make adjustments in the overall length to tune
the antenna to the center frequency you desire using the following information
It’s best to use an antenna analyzer such as the MFJ-259B for determining antenna resonance. Use
the X=0 an +/- j0 readings to determine the resonant frequency. The SWR will be adjusted by
adjusting the length of the top element section.
The antenna resonant frequency may be centered at any point by merely adjusting the overall
length. To raise the base resonant frequency, shorten the element tubing stack. To lower the base
resonant frequency, lengthen the element tube stack.
Plot showing the 40 meter test antenna at 25 feet overall length
