Here's some information that was recently posted on one of our forums. It relates to the proposed increase of EIRP to 1 watt for
low-power FM users:
The introduction of high powered FMBC services above 100 MHz that started in 2001 meant a need for changes to our licence engineering processes by inclusion of coordination calculations between those services with aeronautical radio navigation aids in the band 108 to 117.95 MHz. Discussion of these requirements was included in the technical monograph "TM2001/003 Review of FMBC and aeronautical coordination Issues" which has been available on the RSM web site for sometime. That document notes that the potential for high powered FM stations to cause harmful interference into aeronautical receivers used for Instrument Landing Systems and Variable OmniRange Systems and cause significant operational issues for aeroplanes during landing approaches during poor weather and at night. In some circumstances the loss of these facilities due to harmful interference can result in real safety of life incidents.
To enable the safe operation of these aeronautical services calculations are completed in accordance with ITU-R Recommendation SM.1009. Those calculations include the determination of signal levels for all FMBC services at navigational receivers in aeroplanes, including signal levels for low power FM services above 106.6 MHz and located within several kilometres or so of an aeroplane using the navigational systems.
The current planning being undertaking within our Ministry for the roll-over of high powered FM services licences in 2011 includes the frequency reassignment of many current stations to provide improved FM reception and additional spectrum capacity for new stations. This planning has taken longer than expected and delayed the calculations necessary for the proper coordination of the low powered FM services with the aeronautical navigational services. The recent auction of those new licences will, we expect, mean the end of significant frequency changes and that we can now finalise those coordination processes.
I have recently taken delivery of the necessary calculations for Auckland, Wellington, Christchurch and Dunedin, and plan to review these to ensure all recent frequency changes are included. Once this is completed there will be calculations required for services adjacent to regional airfields before we can finalise areas where use of low powered FM services must be restricted. (Such areas are likely to be close to major and regional aerodromes.)
