
I use the following setup for my AgOpenGPS autosteer system with the free Iowa CORS correction service.
The accuracy here in central Iowa seems to be in the 1 - 2 cm range!
The correction takes place outside the autosteer system so the autosteer system is setup as a generic WAAS type antenna
(but the GPS shows as RTK Fix or Float accuracy). See documentation under pictures.
I have built a DIY base/rover setup for use on an AgLeader monitor.
I have not integrated RTK with Trimble receivers but have instructions how to do it.