Another followup.  I'm successfully used this base station to do some replanting using an FMX and also sprayed several days using a Pro 700/372.  I've had absolutely zero issues with correction stability using the FMX.  Several days ago a gave up and sprayed with RTX because the 372 would not maintain a connection or would loose GPS.  And then I recalled some issues I had when we went to RTX 5 years ago with this setup.  The 372 originally had a 900 mhz radio in it.  When we went to RTX it would drop the signal.  At my dealers suggestion I removed the radio and have not had an issue since.  Move forward to this experiment.....when choosing RTK I am given the choice or Radio or Modem.  I've always left it on Radio thinking it did not matter.  On Thursday I was testing again with my base and while moving to a far away farm I was once again dropping GPS.  I then changed the correction source to Modem and continued on for 4 hours without an issue.  We had originally thought this issue was due to the board not seeing enough trackable satellites but it appears that was not the case.  I may do more testing with my original ZED-F9P board.