- **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. By having two clients you can not only send your position, but also send and receive APRS messages.
- **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
- change **LORAPRS_FREQ** if you are planning to use different frequency or if planning to calibrate clients, currently it is set to **433.775MHz** as per https://vienna.iaru-r1.org/wp-content/uploads/2019/01/VIE19-C5-015-OEVSV-LORA-APRS-433-MHz.pdf
- if you are planning to experiment with different bandwidths/spread factors then modify loraprs.h, with current parameters APRS packet time on air is around **2 seconds** to decode with as lower level as possible, use https://github.com/tanupoo/lorawan_toa to make calculations
- 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
- note, that there a is **significant frequency drift** on temperature changes for different modules, you need to use **external TCXO** if you are planning to use modules for narrow bandwidths less than 125 kHz or calibrate clients based on server frequency drift report by changing **LORAPRS_FREQ**, for example, let client and server run for an 30-60 minutes and if server reports err: -1500, then set client frequency to about 1000 kHz less, e.g. instead of 433.775 set it to 433.774, this will give couple of additional dB
- Successful decodes down to **-17.5dB** below the noise floor when using compressed APRS coordinates (smaller packets, about 50 bytes), see APRSDroid discussions on compressed corrdinates support and custom branches