KK6FAH_Section

When I turned on the radio this morning, my screen remained "blank" for a long while with very few weak traces visible in MAP65. While monitoring the WSJT-EME-1 chat room, many moonbouncers were complaining about the poor conditions. That was the perfect opportunity for me to try the "Moon Echo Project" capability (described in Section 25) in order to evaluate the quality of the EME conditions on that particular day. Since I had performed numerous Echo Tests over the last weeks, I had a pretty good baseline to start with.

After optimizing the polarity of the TX antenna to maximize the strength of the echo traces produced, I started seeing some very weak traces, but most of them were barely visible and very sporadic. See video of the actual experiment to the right. Below the setup that was used for the test:

***WARNING: For Best Resolution, it is critical to select 720p HD resolution in the youtube "settings" at bottom right of the player. The 360p default setting won't yield good enough resolution to see the details. It will take several seconds before the High Resolution kicks in, so you will need to restart the video from the beginning when the High Resolution is active and select to view the video in "Full Screen Mode" for best experience...***

In contrast, a few days earlier (September 2nd), I had performed the very same test using the exact same setup. The conditions were really good on that day and the Echo Traces recorded were of very high quality. See video of the experiment to the right and the detailed setup below:

The 2 videos above are quite interesting. First, the degrade factors between the "Bad Conditions" day and the "Good Conditions" day were almost identical, that is -2.6dB versus -2.2dB respectively. Even the position of the Moon in the sky were quite similar (119.9AZ/42.8EL versus 124.2AZ/51.4EL). On the bad day, the noise level was higher by about 2dB compared to the good day. That is not very surprising since on the bad day, the position of the sun was very close to the moon, that is within 5 degrees for both AZ and EL. Since both Echo Tests were performed after careful polarity optimization of the TX antenna to maximize the strength of the Echo Returns on the RX antenna, the impact of Faraday Rotation can be completely eliminated. Additionally, there cannot be any Non-Reciprocity involved due to the fact that this EchoTest is essentially a "one-way" deal and where the TX polarity was carefully optimized to maximize the Echo Traces on the RX side.

Here we are in a situation where Faraday Rotation and Non-reciprocity are out of the equation, both Echo Tests were performed in extremely similar conditions, and the 2dB noise increase is fairly well quantified and explanable, so how can there be SO MUCH difference in the quality of the EME conditions between these two days? Certainly, the 2dB noise increase on the bad day cannot explain the massive difference in question, since on the good day, Echo Returns in the -16dB to -22dB range were frequently recorded, while on the bad day, most of the time there were no Echo Returns at all and only some rare ones of extremely poor quality, so there is much more than only 2dB degradation involved here.

So the ultimate question remains: What is causing of so much difference in the Quality of the EME conditions between these two days then? That is precisely one of the purpose of the Moon Echo project and related capability. Since all the "known" variables are fairly fix (e.g. degrade) or entirely eliminated (e.g. Faraday, Non-Reciprocity), we have to look at a different explanation...

The "Bad Conditions" day was preceded by several Geomagnetic Storms. That could very well be a major cause and the "Invisible Hand" playing us behind the scene. Other phenomena such as "polarization Spreading" could be at play, but the Echo Tests would have easily detected that phenomenon by getting Echo Returns on a wider range of polarities, so that one is also out of the window. May be some ionospheric absortion phenomenon could be at play here and could have been partially triggered by the Geomagnetic Storms?

If we can determine and quantify the negative impacts of that "Mysterious Cause", then the field of EME would be seriously advanced, and real good Predictions of the EME Conditions could begin to be developed. That is one of the goal of this experimental site and the overall "Moon Echo Project". Certainly, the ability to have separate TX and RX antennas and being able to produce its own Moon Echos "at will" is an extremely useful asset to evaluate the Quality of the EME Conditions on any given day.