You must be on version 1.34 of RXLogger for this feature to work.
You must change the default storage location to /storage/sdcard0/Rxlogger/
Be sure to hit BACK and then SAVE on each setting change.
Stop (if running) and Start RXLogger.  Finally I have a filename.cap0 log.

Thanks for the tips from one of the dogfood testers...I forgot who shared this but it works now.

Mike Holman