Only one problem, in the time since since 2010 my Icom has stopped talking to my computer. So, I have the idea and I need new ways to monitor radio signal strength over time. Technology has advanced baby! Enter SDRSharp and NooElec Software Defined Radio receiver. With SDR your computer does the heavy lifting while an itty bitty usb device receives the signal. I have a NooLec receiver with an HF downconverter. So I can still monitor the airwaves. The SDRSharp software allows tuning and spectrum display. Importantly, it also allows capture of signal strength data.
So, in order to run my experiment I need only boot up the system and record. As I planned to watch the eclipse in Austin, the equipment would have to be left running over several days on its own. As it turns out this is not so bad an option and success was granted me.
Below is the record on the day of the eclipse. Interpretation of signal strength over time is the same as always. The morning and evening sudden signals rise or fall as the ionosphere strengthens above and then dissipates below a critical density needed for propagation. A deep D-layer absorbtion at mid-day attunuates the signal making reception of Ft. Collins difficult to impossible.
In this case though there is another actor in the circuit drama. Near mid-day the moon's shadow passed across the circuit. This shading shutoff the D-layer ionization and, being the lowest of the ionospheric layers, recombination took place rapidly. With that the absorbtion was shut off and the Ft. Collins signal again managed to get through to Houston. The event was short-lived though. As soon as the shadow passed beyond the region the D layer rapidly re-ionized and signal absorbtion returned.
For the rest of the afternoon the D-layer slowly weakened as the sun passed westward. Soon the signal from Ft Collins was comming in near full strength. This continued through the later afternoon until the F-layer too began to dissipate. When the electron density finally fell below critical density the circuit shut off. What a nice story!