RF fields in south Christchurch

The graph below shows measurements of RF fields made in 2012 in a 1 km square of south Christchurch. The area is mostly residential but includes a small commercial development, and contains a cellsite (base station) operated by each of the three New Zealand operators. The main TV and FM radio transmitter serving Christchurch is at the top of a hill (Sugarloaf) about 5 km to the south and 500 metres higher up.  Twenty measurement locations were selected using a random number generator.

Each measurement is shown as a bar.  The height of the bar shows the total exposure at that location, and the coloured portions show the contributions from different types of transmitter. The number at the bottom of each bar shows how far away that location was from the closest cellsite.  

For example, the bar on the left shows a measurement 5 metres from the closest cellsite.  The total exposure at that location was just under 0.045% of the public limit in the NZ exposure Standard (ie about two thousand times lower than the limit).  A little over one half of this was from cellsites, about a quarter from FM radio, an eighth from TV and a very small fraction came from other transmitters (mostly mobile radio services).    

These measurements show the following features:
  • While cellsites generally made the greatest contribution to exposures when the measurement location was within 250 m of a site, this was not always the case.
  • Distance from the closest cellsite was not really a good indicator of what the exposure might be.
  • TV and FM radio typically produced exposures equivalent to about 0.01 - 0.02% of the exposure limit.  
Since these measurements were made, analogue TV transmitters have been turned off, so the contribution from TV would now be lower than when the measurements were made. 

Last updated 29 January 2014