History
A small P25 network has existed in New Zealand for some time.
Pre-standard ASTRO™ system developed by Motorola
Motorola combined their experience with a proprietary 12,000 bps 25 kHz FSK Encrypted Securenet system with Smart Zone analog trunking and developed an air interface modulation standard using 9600 bps 4FSK to fit in 12.5 kHz called ASTRO. The first large scale implementation was with LAPD using the early VSLEP vocoder. The ASTRO system was tested by ZL2TRV (ZL4JY) and ZL2ARW through Belmont 710 in 1995.
Later the APCO (Association of Police Communications Officers) P25 committee worked with Motorola and the TIA (Telecommunications Industry Association) towards an open multi vendor system, first for conventional with common air interface operation then later with trunking. Trunking specification including over the air re-keying and other enhancements and now forms a mature standard. The P25 system benefited from the better IMBE vocoder. P25 was first tested by ZL2TRV (4JY) and ZL2ARW through Belmont 710 in 1997.
Reasonably widely used Amateur Radio standard in USA.
Overview
