1.Building a sub $100 digipeater using Dire Wolf software+Raspberry Pi: https://ewpratten.com/blog/direwolf-aprs/
2. PLXDigi by microsat: https://microsat.com.pl/product_info.php?products_id=54&
3. UIDIGI EPROM for an old TNC2 / Tiny2 TNC :https://aprs.gids.nl/uidigi/
73 Paul ZL2BEZ