APRS 438

APRS 438 logo

Welcome to the home of APRS 438, the 438 MHz amateur radio LoRa automatic packet reporting system that extends range by saving bytes.

Unlike some other ham radio LoRa APRS projects, this project aims at deploying LoRa the way it was intended; namely by being frugal about the number of bytes put on air. Doing so, reaps a number of benefits:

  • less airtime,

  • increased battery life,

  • higher chances of good packet reception,

  • hence, increased range,

  • lower probability of packet collisions,

  • therefore, more channel capacity.

In dense urban environments and/or on flat terrain, LoRa works best when the data payload is kept to a strict minimum. This can be achieved by taking full advantage of all 256 characters available for transmission with LoRa. The APRS frame compression protocols presented in this white paper aim precisely at doing that; for LoRa, or any other data link with an extended character set.

ESP32 firmware adhering to these compression protocols is provided as well:


Unlike the vast majority of other LoRa projects, the firmware of this project employs licensed frequency spectrum exclusive to the use of amateur radio. You need a valid amateur radio license to be able to use APRS 438 firmware. Contact your national government or local amateur radio club to find out how to obtain an amateur radio license.


This document is still subject to change. Check regularly for changes and added clarifications.