The Automatic Packet Reporting System (APRS) employs specific audio frequencies to transmit digital data over radio channels. These frequencies, when modulated onto a carrier wave, represent binary information that can be decoded by APRS-equipped devices. The standard is typically 1200 Hz and 2200 Hz, corresponding to the Bell 202 standard for Audio Frequency Shift Keying (AFSK) modulation. For example, a 1200 Hz tone might represent a binary ‘1’, while a 2200 Hz tone represents a binary ‘0’.
This modulation technique facilitates the sharing of real-time information, such as location data, weather reports, and short messages. The use of these audio tones allows APRS to leverage existing FM radio infrastructure, making it a versatile and cost-effective solution for amateur radio operators and other users. Its development and widespread adoption have significantly improved situational awareness and communication capabilities in various applications, including emergency response and outdoor activities.
