Overview

My goal is to design a simple, cheap and easily replicable hardware to build a 144MHz APRS iGate and Digipeater. 

Sources

I collected two initial hardware resources using ESP32 and SA818:
https://oshwlab.com/APRSTH/esp32sa818#P6 
https://github.com/nakhonthai/ESP32IGate/blob/master/doc/ESP32DR_Simple_Schematic.pdf

and two software:
https://github.com/erstec/APRS-ESP
https://github.com/nakhonthai/ESP32IGate

and I'm now trying to receive some RF APRS messages on 144.8 MHz to test rx capabilities.

First steps (SA818v Transceiver)

I started testing the SA818v 144MHz FM transceiver module, which appeared very cheap (around 15 Euro) and simple to configure. I haven't tested the TX side yet but, after some struggling, I understood that the RX sensitivity (declared -124 dBm) was insufficient  in my situation. In fact two APRS iGates that I received at around -40dBm with my Sdrplay RSP1, were barely listenable and undecodable using the SA818v receiver.

Second solution (RTL2832)

At the same time, as a comparison, I tried to receive using an RTL2832 SDR receiver (NooElec R820T2) which appeared only a little worse than the RSP1, probably because of the reduced number of bits (8 bits vs 12 bits samples).