Packet Radio
RF and the Internet

The Basics of Packet Radio

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APRS (Automatic Packet Reporting System)

The "Where and What" System APRS is a protocol for real-time tactical communication. It isn’t just for tracking vehicles; it’s used for weather station updates, short text alerts, and "objects" (like marking a marathon finish line on a map).

• The Technology: It uses AX.25 packet radio frames. Data is typically broadcasted on a single shared frequency.

• How it Works: A "tracker" sends a burst of data (a packet). This is heard by a Digipeater (which re-transmits it to extend range) or an I-Gate (which pushes the data onto the internet for viewing on sites like APRS.fi).

• Pathing: It relies on "paths" (like WIDE1-1, WIDE2-1) to determine how many times a packet should be repeated by other stations.

APRS is more than just maps and GPS data, APRS can also link to Winlink, send and receive SMS (text) messages, receive weather updates, look up Ham call signs, and so much more.

EchoLink

The "Voice Bridge" System EchoLink allows licensed hams to communicate with other hams via the internet. It effectively bridges the gap between a handheld radio and a computer or smartphone.

• The Technology: It uses VoIP (Voice over IP). It’s essentially a specialized version of Skype or Zoom specifically for ham radio.

• How it Works: * User-to-User: Two hams talk via their computers/phones.

  • Sysop Mode: A ham connects their computer to a physical VHF/UHF radio (a "node"). This allows a person with a cheap walkie-talkie to talk into the radio, have their voice travel across the internet, and come out of another radio thousands of miles away.

• Significance: It is used extensively for "nets" where local geography would otherwise prevent people from hearing each other.