Experimental LoRa APRS ESP32 APRSDroid bluetooth modem and LoRa APRS-IS iGate

Tiny experimental amateur radio ESP32 based LoRa APRSDroid Bluetooth modem and LoRa APRS-IS iGate server.

Can be used in two modes:

• as a LoRa APRS client, you need to use APRSDroid application (https://aprsdroid.org), connect to the modem using bluetooth, data will be re-transmitted through the LoRa radio, this is similar to APRSDroid micromodem - https://unsigned.io/micromodem/, received data will be sent back to the APRSDroid using bluetooth
• as a LoRa APRS iGate server, which connects to your WiFI and forwards received LoRa APRS positions into the APRS-IS network, it also reports client signal level, by appending it into the APRS comment, so you can see your signal reports in different locations

Software Dependencies (install via libraries)

• Arduino ESP32 library: https://github.com/espressif/arduino-esp32
• LoRa arduino library: https://github.com/sandeepmistry/arduino-LoRa
• Arduino Timer library: https://github.com/contrem/arduino-timer

Software Setup

• when setting up APRSDroid, use "TNC (plaintext TNC2)" connection protocol in Connection Preferences -> Connection Protocol
• go to esp32_loraprs.ino and make next changes based on your requirements
  • comment out / remove LORAPRS_CLIENT define if you are planning to run server mode for APRS-IS iGate
  • for server mode fill LORAPRS_WIFI_SSID and LORAPRS_WIFI_KEY with your WiFI AP data
  • for server mode fill LORAPRS_LOGIN and LORAPRS_PASS with APRS-IS login callsign and pass
  • change LORAPRS_FREQ if you are planning to use different frequency, currently it is set to 432.500MHz, which is 70cm band APRS frequency in IARU-1 region, see http://info.aprs.net/index.php?title=Frequencies
• if you are planning to use different esp32 pinouts then modify loraprs.h
  • lora module SS, CfgPinSs, pin 5
  • lora module RST, CfgPinRst, pin 26
  • lora module DIO0, CfgPinDio0, pin 14
• if you are planning to experiment with different bandwidths/spread factors then modify loraprs.h
  • lora bandwidth CfgBw, 20 kHz (to fit into standard 25 kHz channel)
  • lora spread factor CfgSpread, 11 (should decode down to -17.5dB)
  • lora coding rate CfgCodingRate, 7
  • lora output power CfgPower, 20 (max 20 dBm ~ 100mW, change to lower value if needed)
• use 80 MHz ESP32 frequency in Arduino, it will prolong battery life when operating portable, higher CPU speed is not required, there are no CPU intensive operations

Test Results

• Antennas
  • Client - rubber duck antenna or mobile antenna on a car roof
  • Server - UHF yagi indoors
• Range
  • About 4 km when server is 30m above the ground and client is 2m above the ground with rubber duck antenna
  • About 13 km when server is 30m above the ground and client is at some higher point ~40m above the ground with rubber duck antenna
  • About 17km maximum (non-reliable) between base and mobile station with antenna on the car roof
• Signal levels
  • Successful decodes down to -17.5dB below the noise floor when using compressed APRS coordinates