Remote Base Breaks The Rules

An interesting phenomenon has occurred.  It appears the remote base is making contacts above the Maximum Usable Frequency.  MUF is 18 MHz and the remote base just worked two different stations on 21 MHz using JT65.  Refer to the screen snaps below.  In the first frame notice the lines highlighted in red.  Those are packet exchanges with the WOQL Remote Base.  Clearly good contacts with excellent signal reports with time stamps between 2143Z and 2156Z.

Screenshot 2016-04-18 15.59.56

Here is a screen snap of the Digisonde Ionogram at Boulder, Colorado at 2150Z, the same time as the contacts, showing the MUF is 18 MHz.

Screenshot 2016-04-18 16.00.33

Any explanation?  This needs to be dug into deeper.  Is JT65 that good?  Was the MUF in South America higher at the time than it was in Boulder?  Does MUF need to be redefined?  Is it just all magic anyway?


September, 2017 Followup:   QST article calls this phenomenon “an above-the-MUF mode of propagation”. October 2017, page 46 by K9LA.

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