PACKET, also known as FSK300, AX25 or X25, is a packet based protocol derived from AX.25 and HDLC computer network protocols. Packet radio is a synchronous system in which data is transmitted in ASCII character packets.
There are a number of variants that exist. For HF, there is PACKET 300, and for VHF, there are a number of variants, although the most common is PACKET 1200 and PACKET 9600
PACKET-300 uses FSK modulation with a 200Hz shift and a 300 Bd symbol rate (seldom seen with 600 Baud). On amateur frequencies above 30 Mhz, higher speeds such as 1200 and 9600 baud are typically used. In the US, it is illegal for hams to use speeds above 300 baud on frequencies below 28 Mhz due to FCC regulations.
PACKET-1200 uses FSK modulation with a 1000Hz shift and 1200 Bd symbol rate. There are a number of variations that exist of PACKET-1200, including a PSK-based satellite version. PACKET-1200 can be seen in the VHF and UHF bands with indirect FM Modulation. FM bandwidth is 12 kHz
PACKET-2400 and PACKET-4800
These are just some more variants of PACKET that operate on 2400Bd and 4800Bd.
PACKET-9600 uses GFSK with a 4800 Hz and 9600 Baud symbol rate. PACKET-9600 can be seen in the UHF-SHF band. FM Bandwidth is 15 kHz