Skip to main content

'RF Delusions' NAB Presentation Now on Web

After I presented my paper RF Delusions Saturday afternoon at NAB, I promised that I'd post a copy of it online. It is now available at www.xmtr.com/rfdelusions/ in both HTML and Flash formats. Both versions were created using OpenOffice.org Impress.

The presentation addresses common "delusions" concerning broadcast coverage, interference and RF safety. The major focus is coverage. One example illustrates that using data from the azimuth patterns in the FCC CDBS and the standard elevation patterns from OET-69 may lead to significantly different results from those obtained by using the actual antenna azimuth and elevation patterns. (These would include the actual electrical and mechanical beam tilt.) This is one of the more extreme cases and limitations on time and computer resources would make it difficult, if not impossible, for the FCC to study all U.S. TV stations using their actual 3D antenna patterns.

Most interference studies conducted using the FCC software (available on its Web site) with its inherent simplifications and methodology for calculating the depression angle will not show such an extreme difference in signal levels. Ironically, errors are likely to be greater when azimuth and elevation patterns from the FCC antenna database and OET-69 are used instead of actual antenna patterns for studies conducted with third party coverage and interference software that accurately calculates the depression angle. Directional antenna azimuth and elevation patterns should be included with recent TV construction permit applications, but they have to be extracted individually from exhibits attached to the application.