FM and TV antenna heights on Radio History Project records in FCCdata

The REC Radio History Project

When the FCC went from paper history cards to their first computer system, BAPS, they continued to place semi-detailed comments on the daily "broadcast applications" public notice.  These notes were entered into the BAPS system.  Many of those notes did flow from BAPS to the CDBS system in the 1999 conversion.  

Unfortunately, those notes do not always give all of the details we need every time.  Some notes will have more information than others do.  We will use the data from other notes, existing engineering records that flowed over and in some cases, through educated guessing.

On FM and TV records, antenna heights can be tricky.  What we are finding is that the FCC is using the height above average terrain and in some cases, using height above ground level.  

In order to address this, when entering public notice data, we do some additional calculations in the background.  When is all said and done, we end up with four different figures:

  • Site elevation
  • Height above average terrain (HAAT)
  • Radiation center above ground level (RCAGL)
  • Radiation center altitude mean sea level (RCAMSL)

First, we convert any measurement in feet to meters.

Next, we determine the site elevation at the geographic coordinates entered.

Next, we measure the height above average terrain at ground level.

If the public notice shows a HAAT, we determine the RCAGL by subtracting the HAAT at ground level from the HAAT on the public notice text.  

If the public notice shows a RCAGL, we determine the HAAT by adding the HAAT at ground level with the RCAGL.

RCAMSL is calculated by adding the site elevation and the RCAGL. 

During the BAPS era (1978-1999), computers were not always commonplace in doing broadcast engineering.  Surveyors were used to determine the coordinates and topographic maps were used for height above average terrain, elevations and other measurements.  This means that modern calculations of elevations, HAATs and even geographic coordinates may not always match those determined by the hard working broadcast engineers of that era.    The Radio History Project attempts to compensate as much as possible but with that said, you may see some strange results and therefore, we can not guarantee that all information entered in the Radio History Project is 100% accurate but it is a good guide.

Thank you for your understanding.