Recent Antenna Measurements

Statistical analysis of WSPR reports over a two month period indicate that the actual relative gain patterns between antennas 1 and 2 correspond to the modelled gain patterns. The antenna model and simulation results were obtained using the Altair Feko antenna modelling software. Included in the model is the wooden tower and attached structure. The attached structure is a 10-12 foot wooden shed that houses the remote antenna tuner. The wooden tower has minimal effect on various antenna gain patterns, but it does have a notable effect on the each antenna's resonance. Resonance is lowered. The shed has a minor effect in lowering the resonance of the antenna, the primary contributor appears to be the wooden tower. The Feko software slightly underestimates the effects of the wooden tower and shed. The Feko software indicates that the aluminum drip edge installed on the shed does significantly affect the performance of the antennas on the 17 meter and 15 meter bands; this seems to have been validated by the recent analysis of the WSPR reports. As a result, an additional antenna will be added. This additional antenna will be a center-fed vertical dipole 9.4 meters in height fed at the center point with a remote antenna tuner. (Please see station description for details of different antennas in use.)

Having used several different antenna simulation software packages, I have found that the Altair Feko package, in my opinion, is the best available. It provides the most accurate results. It is capable of modelling not only the antenna, but adjacent structures and objects, both conductive objects and dielectrics. Modelling is not limited to wires and tubes, but most any shape and material. It also capable of modelling buried radiators. Feko also allows for programming in complex ground models to include the variation of ground effects with changing frequencies.