This is a project which I cherish a lot and have been working on for a while. It is now finally coming to full fruition and I am very excited about it!
Objective: Produce a reliable "EME Beacon Signal" in order to study and better understand key EME phenomena and Quantify various EME Station Performance Factors. Here are just a few examples of applications:
- True Quality of the EME Conditions at Any Given Time
- Impact of a Station Change or Improvement on the Overall Performance
Principle: The "EME Beacon Signal" generated is in the form of simple "Moon Echos" which are self-produced using "SEPARATE" Transmit (TX) and Receive (RX) antennas, one of which is equipped with Rotatable Polarity Capability (RPOL). The "switching" between the antennas can easily be done using a simple coax relay switch which is activated between TX and RX.
How does this work? Very simple, but let's go through some theory on the reasons why RPOL and separate TX and RX sources are needed... Just like it is the case during normal EME communications, the signal transmitted towards and back from the moon will be shitfted by Faraday Polarity Rotation effect. This explains why EME operators will often make statements like "I can see a very strong Echo right now", just to realize a few minutes later that the Echos are gone...
However, if the RX portion of the Echo Test in WSJT is done with a separate antenna that has Rotatable Polarity Capability (RPOL), the Faraday Polarity Shift can be completely compensated for on the RX side and the Moon Echos can be consistently produced and recorded at any time without being affected or degraded by Faraday Rotation!
That is precisely why this Moon Echo Project uses a separate TX and RX antenna arrangement with at least one them equipped with RPOL capability. In my case, both RX and TX antennas have RPOL capabilities, but only one is really needed in order to make this whole thing works. For instance, an EME practitioner using fix polarity as the TX source (e.g. 4X10H) could setup a Single Yagi RPOL in the backyard as the RX source and that would do the trick!
The pictures shows the 13-element RPOL LFA in my backyard with manual EL/AZ control which is used as "RX antenna". The picture also shows that this RPOL design can be located very close to the ground for easy access. The whole setup can be supported by a simple umbrella base!
Validation and Initial Results:
The theoritical aspect of this project is all nice, but I needed to demonstrate that it was possible to produce reliable Echos with my current antenna array located on the roof (2X14RP/K) as TX source without having to setup another massive antenna array as the RX source which had to be located in my backyard!
Since I had just built a 13-element RPOL LFA, I decided to use this new antenna as the RX antenna and gave it shot... I was not hopeful in the ability to produce reliable Echos with this relatively small setup...
Watch the video of the initial trial where I produced Moon Echos by TXing with the 2X14RP/KW (located on the roof) and RXing with my new 1X13 RPOL LFA (in backyard), and thereafter, RXing the echo returns with the 2X14RP in order to compare the RX performance between both antennas (2X14 vs. 1X13 LFA).
First, I was extremely excited and surprised to see that I could get such good Echo Traces with a Single Yagi 13-Element as RX without any Ground Gain! That new antenna equipped with an I0QM BALUN really worked beyond my expectations. This initial experiment demonstrated to me that this whole project was truly possible with very simple means which is a big deal!
In this initial trial, the results showed that the quality of the Echos recorded on the 13-element as RX was slightly better than when the RX was done on the 2X14, which clearly had a much higher noise level (2-4 dB). This was a very valuable information to me. The question was, is this because of a difference in the antenna performance (LFA vs. Non-LFA), or is the higher noise level on the 2X14 due to the physical location (roof) which may be more exposed to the urban noise.
After this initial trial, by simply swapping the 13-element LFA for a 12-element RPOL Non-LFA (same YU7EF design as the 2X14), I was able to confirm that the noise level between the LFA vs. Non-LFA was very similar, so the cause of the 2-4 dB higher noise level on the 2X14 was most likely due to its physical location (roof), which is much more exposed to urban/local noise. Needless to say that this information was extremely valuable to me, and that the Moon Echo Project had already paid off big time!
The next step with this project is to test how "Sensitive" the system can be. This will be demonstrated in the next sections.
Much more to come, stay tuned!
***WARNING: For Best Resolution for the videos below, 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...***