Is there anybody out there? 500,000 potential listeners…

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• by Duncan Sones

Producing a series of radio coverage maps is the first step towards estimating the size of the range and reach for Farm Radio International’s partner broadcasters. This methodology provides reliable estimates of potential listeners, actual listeners, and a radio station’s broadcast zone.

Farm Radio gathers information from each station on:

• the location of the station transmitter/antenna(e) (using GPS)
• the radio station frequency
• the station transmitter/antenna(e) height above average terrain, (EHAAT)
• the power of the station transmitter (Watts or Kilowatts)
• the gain of the station transmitter (dB)
• the effective radiated power (ERP)

These variables were fed into geographic information system (GIS) mapping software which follows the FCC standards for determining FM radio contours.

The maps are shaded to denote the broadcast reach of each station, with the signal getting weaker further from the station. Population maps obtained from http://www.worldpop.org.uk/ are overlaid with the radio contour maps produced by this method Farm Radio makes calculations of the:

• total potential population – the population in the station’s broadcast coverage zone
• total potential rural population – the rural population in the station’s broadcast zone (“rural” is defined as less than 400people/km2
• estimated adult population, using estimates of adult population percentages in each country from the UN,

The reason this method is used is because radio stations in sub-Saharan Africa do not have accurate or recent estimates of their coverage area.

Radio five coverage map

Radio Habari Njema coverage map

500,000 potential listeners: using the mapping method described above, FRI estimates that the two radio stations used in the first campaign have reached over half a million potential listeners:

Habari Njema and Radio 5 are partners in the delivery of Scaling-Up Improved Legume Technology (SILT) project.

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