Regarding the UHF radios with the RS3 is compatible with the TRIMTALK protocol, you can establish RTK communication between the Reach RS3 and a third-party base. For this connection, the Reach RS3 will need a 410-470 MHz UHF antenna.
The Reach RS3 supports correction input and output exclusively in RTCM3 messages. Therefore, it is essential to configure the third-party base or rover’s message type as RTCM3.
We have this Support Tip post on the Community Forum detailing more about the RS3 working with UHF Radios.