Our radio for S100 has gone through several revisions.
First model use E61-433T30D 433MHz 1W UHF radio with Raspberry Pi Zero.
First revision used a USB host to replace Raspberry Pi Zero when there was supply issue.
Current second revision uses 915MHz 1W Lora radio to replace E61-433T30D when it reached product end of life.
At the limited line-of-sight test environment near our office, we are only able to verify ~10Km operating range at 21dBm default output power. Since it's a 1W radio with 30dBm maximum power, customers that need longer radio operating range could increase the output power level through software configuration.
Using a pair of radio enables possibility of performing RTK survey at places without RTK correction service or Internet connection. This is only possible using dual-frequency RTK receivers with raw measurement data logging capability such as S100. Below blog written back in 2020.12.03 shows how this can be done.
https://www.polaris-gnss.com/blog/rtk-survey-without-using-gnss-correction-service
Lora radio user guide available here: https://www.polaris-gnss.com/S100_Radio_Ver3_Quick_Guide.pdf
Lora radio can be ordered here: https://www.polaris-gnss.com/RadioShop
For Brazil customers, due to excessive ~100% customs duty tax, it'll be better to order from our Brazil distributor AgroData, https://agrodata.me