As widely known, lunar surface communication.（EME）It's a mode that requires high-quality equipment, and it's QGX's favorite. In the past two years, I successfully used a single 17-element Yagi antenna with DL7APV, HB9Q, and NC1I to achieve basic EME communication in the 432 MHz band. However, this was just a first step. Typically, EME in the 50, 144, and 432 MHz bands requires large Yagi antenna arrays (with 1296 elements, parabolic antennas are primarily used). Traditionally, Yagi arrays with more than two antennas are generally mounted on fixed towers with turntables due to their large overall weight and complex structure. Therefore, after the tower designated for the 144 MHz array was determined, I didn't consider upgrading my antenna for the 432 MHz band for a long time.
However, a single antenna ultimately lacked the power! The frustration expressed by DK3WG ("no EME performance") (although not directed at me) was understandable. The unfortunate experience last year, where I attempted to communicate with him and UA3PTW (a powerful Russian station), but failed to establish stable contact despite being able to receive CQ, was truly disappointing. So, when everyone in the EME group was researching 4-antenna array solutions, I wasn't idle either. It was about 4 months ago that I stumbled upon this:
I immediately forwarded it to the EME group chat and exclaimed, "This seems to directly solve the problem of stacking distances up to 1.6 meters! You can use any type of crossbar, and if you install four of these, you'll have a complete, foldable H-frame!"
Hey, after thinking about it further, it seems like that's actually the case? If a foldable design means easier portability, then this could be really useful.It seems like there's a real possibility of creating a self-supporting array!
After carefully considering the specific plan over the next few days:
The first question: How many antennas make up the array?
An array consisting of four long main boom antennas is the most popular choice in the EME (Experimental Mode) community. However, my experience setting up a 4-meter long main boom antenna on a portable base suggests that this may not be suitable for a single-operator setup. As a method of space communication, EME requires the antenna to be movable in both azimuth and elevation directions, so the longer the main boom, the higher the required height. A simple geometric calculation shows that if a 4-boom array with a 4-meter main boom is used, the horizontal booms must be at least 2.6 meters above the ground to ensure that the antenna is at least half a wavelength above the ground, which creates two major problems:
Firstly, the support system for an array antenna requires extremely high reliability, which means that lightweight masts previously used for single Yagi antennas are no longer suitable.We need to purchase heavy-duty lamp stands similar to those used for shortwave Yagi antennas.This also has a significant impact on the portability of the entire system.
Secondly, after raising it to a height significantly exceeding human stature.A manual pan/tilt mechanism will be difficult to control.However, electric gimbals are heavy and involve a range of issues related to power supply and control.
Under the assumption that the target gain remains approximately the same, the main beam length of an 8-element array is only half that of a 4-element array, and the spacing between stacks can also be reduced appropriately. Although the entire support system needs to be widened by about twice its original size, its length and height can be significantly compressed, resulting in a direct halving of the required height.This allows you to directly use commonly available, heavy-duty tripods as support (without having to purchase expensive and specialized heavy-duty lighting stands), and also eliminates the need to consider electric rotator issues.
The second question: What is used to fix the antenna to the table legs?
When installing a fixed-mounted Yagi antenna, the connection between the antenna and the support pole is typically achieved using clamps. I was particularly impressed with the convenience and stability of Ak's quick mount clamp when setting up a single 4-meter Yagi antenna previously. Fortunately, there was also a screw hole at the bottom of the table legs that could be used to connect the quick mount base. This allowed me to elegantly attach the quick mount base to the leg using screws, and then use the quick mount base to secure the antenna!
Third question: What type of antenna should be used?
According to the established design principles, the antenna should adopt a short main beam design. Another point is that antennas with a 50-ohm impedance are more advantageous for ground-mounted installations due to their simple and robust impedance matching structure. In terms of performance, our transmission power cannot reach the same level as foreign stations due to well-known regulations and equipment limitations (the absence of external high-power amplifiers). Furthermore, based on past experience, the noise floor in our local 70cm band is not particularly high. As a member of the school's radio club,（BY1QH）The highest gain antenna system available in the recently accessible 70 cm frequency band, should also consider the potential future needs of the association for receiving experimental signals from the amateur satellite "Ring Moon".
Therefore, when selecting antennas,The selection range is limited to a Yagi antenna with a 50-ohm impedance and a main boom length of 1.5-2 meters. The initial focus should be on maximizing transmission performance through gain, followed by reception performance (front-to-back ratio and noise temperature). Additionally, the bandwidth should ideally cover 432-438 MHz.The final confirmed antenna model is GTV70-10w from DG7YBN.Single element gain of 14.1 dBi, simulated array gain of 22.9 dBi.
In terms of production, the antenna continues to be manufactured by our long-time partner. @bg7xwf Sub-assembly: The main beam uses aluminum pipe connections, featuring a spring quick-release and damper storage design. It can be disassembled into two sections, each with a length of 1 meter.
As a result, the plan began to take shape:
The cross-section is formed using a 3-meter aluminum tube as the boom, with eight 50cm folding table legs installed on either side as the supporting elements. This creates a 3m x 1m H-frame structure. At the ends of the folding table legs, quick-mount mounts are attached using the existing screw holes, securing the antenna. This completes the support structure for a 4x2 Yagi antenna. To assemble, simply connect the boom, extend the eight table legs, and then "clamp" the eight antennas (with pre-installed quick-mount brackets) onto the quick-mount mounts.
In this design, all parts can be divided into segments no longer than 1.3 meters and carried in a bag or transported using a small shopping cart. The antenna was originally planned to be kept intact for storage and transport, but it was later found that when the main beam is disassembled and the resonant part is stored without removing the form that excites the resonance, the shape of the antenna is extremely similar to a 41-inch guitar in both appearance and size. Therefore, we successfully tried putting eight antennas into two guitar cases! (See diagram below)
The scheme is named:Compact Integrated Array of Low-noise-yagis for Lunar-reflection Operation (CIALLO) Common name: Portable Multiple Yagi System (MYGO) (for heavy fog conditions)
Once we had the plan, we started to implement it and place orders.
Purchased the first table leg and quick mount base. Used the existing long main beam antenna, with a total length of 2 meters divided into segments to simulate a short main beam antenna. Tested installation stability:
During testing, it was found that the plastic component at the end, which is held in place solely by its own friction when inverted, has a risk of detaching. Therefore, epoxy AB glue was used to encapsulate and fix it:
After the glue was applied, it was much better; there was no longer any immediate danger of falling.
Measure the dimensions of the hole for the table legs, and then order a crossbeam with pre-drilled holes and corresponding inserts from BG7XWF.
I've applied glue to all eight table legs and assembled the entire support structure. The clamp, which my friend BA7LVG helped me make, has also arrived. I'm now testing the tripod by extending it.
Bangguli: Buy enough at once! (The picture only shows 4, but if you order 8 together, they will arrive at the same time)
After disassembly, store the 8 Yagi antennas in two guitar cases. Could you provide a 70cm band for my entire life?
In a very crude mannerInstall the power divider and LNA (to be optimized later)
Indoor deployment testing has taken shape! (Due to space limitations, only four antennas were installed in the center, which laid the groundwork for a later development.)
Finally, on April 5th, the CIALLO cannon completed all preparatory work for deployment and was ready to go. Around 8 PM, QGX and his companions were @BI1TEK We carefully moved the complete equipment, weighing approximately 30kg, to the designated site using a small trailer. While the trailer was relatively elegant for transporting the equipment, it was still somewhat undersized and couldn't accommodate the entire system; I carried the radio on my back, while TEK carried the guitar case (containing the antenna).
Proper installation, everything went smoothly at first, but when installing the four external antennas, although one person was holding the opposite side to account for torque, a large amount of torque still occurred due to improper operation, and "pop!" The 3D-printed Akka clamp broke at the point of stress concentration.
Fortunately, this fixture had undergone a previous version iteration during testing, so there was a backup unit. Based on the lessons learned from the previous experience, I installed the outer 4 antennas before mounting the base and then installed the inner 4 antennas after mounting the base. This time, there were no further issues. During the installation process, BY1QH's @BH9DWE 、BH1VLK and @BH8GEJ The three old friends also joined the fight one after another. They formed a five-member girl band.
However, this backup antenna was eventually discarded for a specific reason: its mounting plate lacked any limiting devices, making it prone to accidental sliding. This was manageable when the antenna was in its parked position (pointing towards the zenith), but became precarious once it was pointed at the moon, requiring manual support. In this state, BH1VLK successfully established communication with Swiss station HB9Q. At that point, BH1VLK thought of using two additional tripods to share the weight of the antenna array. Finally, a complete 8x10 array, supported by three tripods, became stable. "Moon shot, initiated!"
Ultimately, over approximately 2 hours of setup time, we achieved two-way communication with HB9Q, OK1VUM, and ON7EQ. We also received transmissions from SM4GGC, which was being transmitted by DL1VPL (this essentially covered all EME radio stations using a 432MHz antenna array at that frequency).It is worth noting that ON7EQ, with whom we successfully made contact, was not a "superpower" but rather an ordinary EME enthusiast. His antenna consisted of a 4x19-element Yagi array, which was similar in scale to our system.This means that we theoretically have the capability and configuration to complete EME communication with a radio of the same type, and are only one step away from completing the Echo (backscatter) technology.
Writing a discussion as the ending of a story seems a bit strange (e.g., "This leaves room for further discussions at next year's amateur radio conference"), so let's conclude with a favorite quote: "Per ardua ad astra."
The common translations of "Through this arduous journey, reach the heavens," are not entirely accurate because engaging in amateur radio is primarily about finding enjoyment. Furthermore, we can easily achieve "unlimited reach" using other communication methods. — However, another translation, "doing everything possible to reach the stars," could also be used to describe QGX's efforts over the past four months on Project CIALLO.
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