Continuing my exploration of phase information and signal processing, I put up a temporary second antenna to feed my second receiver so that I could compare the signals in two spatially separated antennas ...

I was setting up for a jt9 session on 15 meters, when I heard the familiar quick chirp of an oblique ionosonde sweep by. I'd played with these signals many years ago, programming my hp65 calculator as a timer to sort out the various stations in their mostly regular repeating schedules. It struck me that these signals would make an interesting subject for my continuing phase analysis project...

Last time I looked at simultaneously recorded WWV signals on 10 and 15 MHz to see if there was any correlation between their phase variations due to propagation. The phases in each varied, but there didn't appear to be any common features in those variations. Five Mhz is evidently so large a frequency separation that the corresponding refracting portions of the ionosphere aren't very correlated.

There aren't any WWV frequencies that are closer together than 2.5 MHz, but we aren't stymied yet. WWV transmits more than a carrier ...

I have the optional RX2 module installed in my Flex radio which gives me an independent second receiver to work with.  Well, not quite independent - it uses the same TCXO as a reference for its second DDS (direct digital synthesizer - the thing that sets the received frequency), so the two frequencies are in effect phase locked. This is a good dependence because it gives me a way to look at what is happening on two different WWV frequencies at the same time ...

​In the last post, I used a rule of thumb to estimate that my receiver system was stable enough so that it didn't contribute significantly to the slightly varying frequency signal from WWV due to propagation. It would be nice to verify this and maybe measure the actual stability of my receiver in the process.

Since propagation is apparently the source of the variability in the WWV signal, I need to measure a signal not affected - at least as much - by the ionosphere ...