VHF Communication 25kHz Channel Spacing
Airservices Australia released a Discussion Paper on 12th November 2004 seeking industry’s views on the proposal that for VHF communications equipment in aircraft the 25 kHz channel spacing (720 channels) standard be mandated in Class A airspace from November 2005 and for flights in all other airspace categories from November 2006.
Proposal and Survey Results
Concurrently with the Airservices’ Discussion Paper, CASA released a ‘2004 Aircraft Equipment Survey’ which collected data on aircraft equipment fit including VHF communications radios. The results of the Airservices’ Discussion Paper survey and CASA’s Survey are available in the detailed Outcomes and Recommendations.
Recommendations
Based on industry consultation and especially with the view to minimise the financial impact on industry, the following recommendations are planned to be implemented:- Airservices will begin assigning 25 kHz channel spacing frequencies (in the range 118-136 MHz, i.e. 720 channels) for Class A airspace frequencies from November 2005 beginning in areas of high traffic density as needed. This will not involve mandated change to equipment fit for aircraft. (In reality aircraft operating in some Class A airspace may continue to use 50 kHz radios for a number of years.)
- Airservices will begin assigning 25 kHz channel spacing frequencies (in the range 118-136 MHz, i.e. 720 channels) from November 2006 beginning in areas of high traffic density as needed (mainly Class C, D and E airspace). 25 kHz should only be introduced in Class G (including CTAF and MBZ) after other frequency planning options are exhausted. This will not involve mandated change to equipment fit for aircraft. (In reality aircraft operating in a significant portion of Australian airspace may continue to use 50 kHz radios for a number of years.)
- CASA to enable regulation to mandate the transmitter frequency tolerance standard of 30 ppm for all aircraft transmitting radios (including Class G) from November 2009. (Some 50 kHz radios can support this tighter tolerance and therefore in practice some aircraft may continue to operate these radios in low traffic density areas of Australian airspace for a number of years.)
- Airservices to consider identifying (by a notation) in AIP documentation (until CASA mandates the new standard in 2009) any frequencies on 25 kHz channel spacing.
Questions
Airservices Australia is responsible for managing the assignment of frequencies in the band. If you have questions relating to 25 kHz channel spacing in general please send them to: spectrum.manager@airservicesaustralia.com
CASA is responsible for setting standards for aircraft equipment. If you have any questions relating to aircraft equipment and fitment associated with the 25 kHz change, please send them to: vhf25kHz@casa.gov.au.