Elaborated between 1978 and 1984 by the radio-amateur community, PACKET is an AFSK mode as AMTOR (see above). In 1200 bauds, it allows to acceed in VHF to BBS (Packet servers). It is a mode which allows the transport of APRS (Automatic Position Reporting System) frames.
Baud rate : 300 for use in HF and 1200 for use in VHF.
Speed : about 330 wpm at 300 bauds and 1320 wpm at 1200 bauds depending of the number of repetitions
Modulation : FSK two tones (« mark » and « space ») with a shift between tones of 200 Hz at 300 bauds and 1000 Hz at 1200 bauds (fixed tones at 1200 and 2200 Hz)
Reception mode : USB ou LSB for HF (300 bauds), FM for VHF (1200 bauds)
Character set : ASCII characters + ANSI extended characters
Shape of pulse : rectangular
Bandwidth : 900 Hz for the 300 bauds mode and 3400 Hz for the 1200 bauds one
Demodulation : non coherent
Synchronization : automatic using the signal
Correction code : no
Convolution code : no
Interleaving : no
Pmean/Ppeak : 1
AX25 protocol (principle) : all the communication is done through "frames" (limited set of characters). There are different sorts of frames (information , supervisory...) which allow to connect, to do the communication (through an automatic procedure of transfer and anknowlegment) then to disconnect.
+Good for networks
-Not real sensitive even at 300baud
-Not to many people on HF using 300 baud packet
+Popular in the VHF bands at 1200 baud
Mode Audio Sample
FFT Window Screenshot