The rover was configured for serial input, and you were right, I forgot to set the baud rate. If you start it in serial mode first, then it sets the baud rate, but if not then you must set it yourself.
After setting base output to tcpsvr and starting the base, use your smartphone to open a terminal window and connect to the base with:
ssh root@reach.local screen stty -F /dev/ttyMFD2 57600 nc 127.0.0.1 9000 | tee my_base_log.rtcm3 > /dev/ttyMFD2
open second terminal window and:
ssh root@reach.local screen -d exit
go back to first terminal window and:
exit
Now set rover input to serial and start it and get to work.
When you are finished and want to stop the base log, go back to the base and:
ssh root@reach.local ps | grep SCREEN kill 619 # or whatever the PID is for SCREEN exit
These commands were picked to avoid the use of the CNTRL key mainly because it is not supported in my Android terminal emulator app.
I have not tried tmux yet, but it seems very similar to screen.