Take a look at rtklib.com for software and instructions on https://wiki.openstreetmap.org/wiki/RTKLIB https://wiki.openstreetmap.org/wiki/RTKLIB. There are quit

Take a look at rtklib.com for software and instructions on https://wiki.openstreetmap.org/wiki/RTKLIB https://wiki.openstreetmap.org/wiki/RTKLIB. There are quite a few u-blox receivers that work, also receivers from other brands. If you want to try dual frequency for improved accuracy, u-blox launched an affordable dual frequency chip in 2019.