Thanks all.  I think I have my iPhone compass "on" and calibrated now.  I tried using the "Compass" app on the phone and it was unresponsive.  I went into Settings - Privacy - Location Services and changed the Compass App to "While using".  Still it was not responsive.  Then at the bottom of Location Services is "System Services".  I went there and switched on "Compass Calibration" and now at least my phone's compass seems to be working.  I also recalibrated the compass on the drone.  I'll find out today when I fly (winds permitting) if all that helped at all.