Appendix C: Optimising Congested Sites

A study has been undertaken on how to optimise the spectrum use at the major broadcast transmitter sites. The objective was to migrate licences out of the band 915 to 921 MHz and maximise the use of the bands 849 to 851 MHz and 929 to 935 MHz. The results provide a basis for developing specific migration plans once the licences to be migrated out of the band 915 to 921 MHz have been identified.

The study assumed that all the current licences needed to be migrated out of 915 to 921 MHz.

In Christchurch there are 6 x 500 kHz and 9 x 250 kHz licences in this band. It was found that by optimising the assignments of existing licences, 11 of the licences in 915 to 921 MHz could be accommodated in the adjacent bands. The remaining 4 would require further consideration.

In Wellington there are 8 x 500 kHz and 8 x 250 kHz licences in this band. It was found that by optimising the assignments of existing licences, 4 of the licences in 915 to 921 MHz could be accommodated in the adjacent bands. The remaining 12 would require further consideration.

In Auckland there are 10 x 500 kHz and 5 x 250 kHz licences in this band. It was found that by optimising the assignments of existing licences, 1 of the licences in 915 to 921 MHz could be accommodated in the adjacent bands. The remaining 14 would require further consideration.

Other factors which would be taken into account when developing the final migration plans include:

1. Are some licences to be changed to digital STLs operating in the proposed new bands?
2. Should some licences be migrated to a 400 MHz licence because they are providing narrow band, mono services for AM stations?
3. Should some licences be migrated to alternative technologies because they are providing several programmes over one path?
4. Is increased isolation apparent between antennas at the receive site due to buildings and antenna separation?
5. Are other solutions possible using improved site design such as higher grade antennas and r.f. filtering?