Beacon Predictions / Type 13 Antenna Files

Posted by James Watson on 10 Jun, 2018

In addition to isotropic radiators, the ITURHFProp application supports 'Type 13' antenna files, large text files tabulating antenna gain vs azimuth, elevation, and frequency. Although the use of Type 13 antenna promises greater accuracy compared to isotropic radiators, it does at the expense of processing power. The use of an isotropic radiator requires one ITURHFProp run for each beacon, i.e. eighteen runs are required to compute the propagation prediction table. As each Type 13 antenna file is frequency specific, each run can only contain a single frequency, increasing processing time by a factor of five, i.e. ninety runs are required to compute the propagation prediction table. The beacons page now offers users the ability to define a Type 13 antenna, based on PA0PVL's NEC model if required. The following figure illustrates the calculated variation in antenna radiation pattern.

Cushcraft R5 Radiation Patterns

If the simpler isotropic model is preferred, a transmit gain of 0.17dBi is assumed, this being the average of the maximum gains for a Cushcraft R5 antenna at each of the beacon frequencies. As this is an average of maximum gains, it will tend to be optimistic, something that judicious selection of receive antenna gain may correct.

A second enhancement to the page makes it possible to save the prediction table to a .pdf document in one of two formats; a single page chart for two-hourly intervals (similar to the predictions produced by Steve Nichols G0KYA ) or a multi-page document containing forecasts for each hour. I'm hoping to add additional formats, including colour, shortly.


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