Questions related to sending digital data over amateur radio including hardware, protocols, and related software.
What is Packet?
While the term can apply to a specific digital mode, it is often used a general label for digital data modes in ham radio.
The term "packet" refers to "packet switching", the basic structure of the network protocol used to transfer information. This is the same basic protocol that runs the Internet. In fact, the common packet protocol is AX.25 a derivation of the Internet's X.25 protocol.
As one of the first "modern" digital modes, packet radio transmits data in groups or "packets" of 10s or 100s of bytes. This allows improved throughput and error control. Transmission speeds typically range from 300 bps on the HF bands to 1200 and 9600 bps on VHF or UHF.
Other Digital Modes
PSK31 is probably the most popular keyboard to keyboard digital mode in use today. PSK31 is normally generated and decoded using PC soundcards with one of many available software packages. PSK31 occupies very small bandwidths (approximately 100 Hz) and offers effective communication at low power. PSK31 uses Phase Shift Keying for data encoding
RTTY (radio teletype) is the original keyboard to keyboard mode, based on the 5-bit Baudot code and it began with mechanical teletypes. It is still a popular communications mode, but now uses PC soundcards for coding and decoding, using 170 Hz frequency shift keying at a 45.45 baud rate -- 60 words per minute.
For More Information
There are many many others. See: HF Digital Modes on Ham Universe for a tabular list of the more popular software packages and the modes they support with links.