The TAP Pattern Distortion Module may be used to compute the distortion of an omni-directional antenna when the antenna is side-mounted on a vertical tower. The Pattern Distortion module will model the horizontal plane pattern distortion of a side mounted, vertically-polarized, omni-directional antenna when mounted on a metal tower structure. It uses the mounting orientation and distance from the tower, as well as the size and type of tower, frequency and nominal gain. This modeled pattern can then be plotted and saved to the antenna pattern library and used later to improve accuracy when calculating area coverage. A Tutorial Video is available.
The pattern distortion is computed on a model developed empirically by The Antenna Specialists Company in Cleveland, Ohio. Antenna Specialists developed the model over several years based on over 3000 measured patterns of various antennas in different mounting configurations. The model assumes a single, vertically polarized antenna with no other nearby passive radiators installed for directivity. The model treats the tower legs as passive radiators that affect the pattern. Note that other features on the tower, such as a ladder or transmission lines, or other antennas, may also act as additional passive radiators that affect the pattern, but are not treated by this model.
You should consult the manufacturer of the antenna(s) you plan to use for any particular characteristics of the omni-directional antenna you plan to use. While this program is a useful tool for predicting pattern distortion, this is never a substitute for a measured pattern from the antenna manufacturer. Note that no vertical pattern is computed for the antenna. However, vertical (or “elevation”) pattern information can be entered manually using the TAP Antenna Manager.
The Antenna Specialists model was developed using antenna mounting spacing from 0.5 feet (6 inches) to 7 feet. The effectiveness of the model has not been thoroughly tested outside of these limits. It is recommended that no antenna mounting spacing less than 0.5 feet (6 inches) be used to avoid effects of capacitive coupling between the tower and antenna.
Complete details on the operation of the Pattern Distortion Module in TAP are included in the built-in software help. For more information on the Pattern Distortion module, click here or contact firstname.lastname@example.org.