I always wanna a real gateway since I meet LoRa, I've using it to transmit data from high altitude balloon for a long time, and amazed by the performance.
But I'm limited by the fact that without a real gateway, I could only have a single channel transceiver, which limit to a specific frequency and Spread Factor, thus I cannot receive two balloons at the same time.
For LoRa gateway, Semtech provide SX1301 and SX1308 baseband IC, both chip can provide up to 49 LoRa decoder, so I can build a 8 freq x 7~12 SF decoder in a single chip, baseband IC also needs RF frontend, Semtech provide SX1255 for 433Mhz band and SX1257 for 900Mhz band.
Normally I can buy LoRa gateway from some factory, but there is two problems,one is that when the project started, there is no gateway for 433Mhz band, and the other problem is that it is very hard to buy one, or the price is too high.
So I try to build one.
Current version is made for Raspberry Pi Zero and a variation for Raspberry Pi, using SX1301 and SX125X.
For Raspberry Pi Zero, the current version only have one SX125X connected to SX1301, which limited the bandwidth to 0.8Mhz, also since I remove Radio_A, lib from Semtech needs to be modified.
For both of the boards, the TX/RX line is separated, and there is no PA/LNA at TX/RX, but I did put a SAW filter on RX, it is because I want to use with external LNA right under antenna.
Also, there is a MAX-7Q GPS module for accurate timing and PPS is connected to both RPI and SX1301, so that RPI can use as NTP server.