Bob,

This is the third time that I’ve noticed Dex’s signal peaking substantially (>15dB?) starting around 0500, at approximately the same time that your signal begins a substantial fade. I’ve seen this twice on captures from Hartmut’s grabber, and once on a capture from Mike’s grabber.

An interesting example is 21 October 2013, when captures by Henny, Mike and Hartmut all showed a fade of roughly 10-15dB in your signal from 0500-0530, with Mike’s grabber (which showed Dex’s signal clearly around that time) showing a rise in Dex’s signal of roughly 10-15dB.  

I wonder if this could be attributable to modal phase reinforcement/cancellation near the terminator? The relative change between your signal and Dex’s seems rather high for that mechanism, but I suppose not out of the question. AGARD CP 305 includes a paper (Morfitt) with some interesting plots in this context, and a number of other papers with interesting propagation studies at frequencies near 74kHz; is there a good place for me to post info of this type?

73,

Jim AA5BW