Packet Radio

If you’re exposed to ham radio for any length of time you are sure to hear some discussion of packet radio.

t8b11

Without going into much detail, we’ll present a big-picture description here.  Just enough for you to have a basic grasp of what’s involved and give you some idea of how it might apply to you.

Packet radio is a generalized term for a digital communication mode where data is sent in bite-sized chunks (packets) via radio.  The transmission and receipt of packet data is largely automated and features data error correction for reliable messaging.

t8d08

Packet radio (sometimes shortened to just packet) blends radio and computer technologies together.  Sounds complicated but it really isn’t.  All you need besides your normal ham radio transceiver is a household computer and an interface between the two.  The heart of this interface is a Terminal Node Controller (TNC) which is an intelligent modem that converts text to audio tones and vice versa.

hal-with-tnc

t4a06

Packet radio can be used between hams directly in real-time (peer-to-peer or keyboard-to-keyboard) but is more commonly used to send messages that can be retrieved on demand.  This operates more like email or mobile phone text messaging.

Slow data rates (typically 1200 baud) make large messages impractical, so packet messages should be relatively short and not have any large files attached.  120KB is the max message size accepted by some big message servers.  A 4KB message will transfer in 2-2.5 minutes under ideal conditions at 1200 baud.

Particularly useful for emergency communication (EmComm) messages, packet radio is predominately used on VHF radios (more local) but can be sent over HF bands Continue reading