Projects using the SI4463

• Little Free Radio: various data rates (and likely also packet lengths)
• SPACE-HAUC Ground Station UHF and their linux driver
• Eleph

Commercial products

Kiwi-tec LAP-E01

• Works in 920.6 ~ 928MHz band, +13dBm, Japanese TELEC certification.
• Uses Speex codec, which as demonstrated below (doesn't perform as well as Codec2 on low bit rates:
  • Speex samples page  : 4kbps sample
  • Codec2 samples page : 2.4kbps sample
    
• 125kHz bandwidth LoRa
• Internal antenna : -0.4dBi

Prior art

nRF24 based

1. Long Range Arduino Based Walkie Talkie using nRF24L01 : many similar projects, all using the RF24Audio library.

RFM12 based

1. Walkie Talkie Duino using RFM12B "open source" (only to the Kickstarter backers).

RFM22 based

Codec2WalkieTalkie

Analog FM based

1. DRA818V analog FM module (lots of harmonics, will need a license to operate)
2. Auctus A1846S : HamShield (by Casey Halverson), also available in Mini version.
   1. HamShield on Tindie
   2. Kickstarter
   3. Hackaday.io
   4. Instructables
   5. Github
   6. InductiveTwig

Comparable projects

KISS modem interface

• https://github.com/sh123/codec2_talkie

LoRa

HamShield LoRa (by Casey Halverson)

STM32

• https://www.digikey.com/en/maker/search-results?&k=getting%20started%20with%20stm32
• NucleoTNC
• https://github.com/x893/Codec2WalkieTalkie
• 1024kHz FIR filter for sampling audio downto 4kHz
• QMESH
• Uses libcorrect as FEC library

ESP32

• #ESP32 Walkie-Talkie 
• ESP32_Codec2 : using a LoRa radio
  
• ESP32 LoRa DV Handheld Transceiver