"Radio Waves on the Moon: A Fascinating Journey with EME Communication"
Author: Qin Bo Shan（BH6QBC）
Introduction
To be honest, this title is quite ambitious, and it's a goal that many people share. However, when I started researching this topic, I found that a lot of information was lost due to its age, such as Professor SY's "EME Ground Wave Communication." Furthermore, there are currently no readily available alternatives in China. Many resources had to be sought out individually online. Despite these challenges, I embarked on my EME journey. While it has been difficult, the results have always been positive, and I have already achieved echo (although I haven't started actual communication yet, haha). Some of you might be wondering why I would attempt to tackle a topic that so many others have not: Therefore, I want to say that if there are any areas where my explanation is lacking or could be improved, please feel free to join the discussion. This is also the purpose of creating this post – because truth emerges from discussion and debate. Okay, let's get straight to the point.
I. First Encounter with EME: A Dialogue Across the Stars
In the vast universe of radio, EME (Earth-Moon-Earth) communication is like a conversation that spans across interstellar distances, connecting amateur radio enthusiasts on both ends of Earth. It's not just a technological challenge; it's also an exploration of the human spirit. For those new to the world of amateur radio, EME communication might seem daunting, but with the right methods and techniques, this journey into space is within reach.
II. Equipment Preparation: Building Your Space Communication Station
(1) Message Sending and Receiving Device: The "portal" for sound transmission.
The transceiver is a core device for EME communication, and it needs to have high sensitivity reception capabilities and stable frequencies. Here are some good options:
- ICOM IC-910H
- KENWOOD TS-2000E
These devices are capable of capturing extremely weak signals, ensuring smooth communication.
(ii) Power Amplifier: The "boost" for the signal.
The power amplifier provides additional energy to the signal, helping it travel through space. The following devices are capable of outputting up to 500W or even 1200W, providing strong support for signal transmission (of course, these amplifiers only exist in my imagination; in real-world conditions, you can ignore this section and simply use it as a rough introduction):
- Elecraft KPA-500
- Ameritron AL-1200
(iii) Front-end Amplifier: The "Guardian" of Weak Signals
The front-end amplifier is installed near the antenna, allowing it to amplify weak signals and reduce noise interference. The following models have extremely low noise coefficients, making them ideal for EME communication:
- Mini-Circuits ZFL-500LN +
- Down East Microwave LNA-144
Please noteThe models recommended above may have better alternatives, so please don't blindly follow trends and choose based on your own needs.
(4) Antenna: The "wings" of the signal.
The antenna is crucial for both transmitting and receiving signals. Yagi antennas and dish antennas are common types. Yagi antennas are well-suited for the 2-meter band, while dish antennas are better suited for higher frequency bands. Building your own antenna not only saves costs but also allows you to better understand how it works.
Three. Software Configuration: "Commander" by Tonglian
(1) WSJT Software: The key to embarking on EME (Earth-Moon-Earth) communication.
The WSJT software is an essential tool for EME communication, supporting various modes such as JT65 and enabling communication even with extremely weak signals. After installation, you need to enter your call sign and grid location, configure the audio input and output devices, and synchronize the computer's time to ensure it stays in sync with UTC time.
1. Installation and Configuration
- Download and install: Access The homepage of K1JTDownload the latest version of WSJT. Run the installer, select an installation path, and create a desktop shortcut.
- Basic configuration：
- Enter personal informationIn the "Options" menu, enter your call sign and grid location; this information will be used for identification during communication.
- Configure audio devicesSelect audio input and output devices, ensuring that the gain settings on the devices are appropriate to avoid distortion.
- Calibration time: By using software such as Dimension4, it's possible to synchronize computer clocks with an error of no more than 1 second. Accurate time synchronization is crucial for EME communication.
- Choose modeIn JT65 mode, the software automatically encodes your text information into an audio signal and then transmits it via a transceiver. It can also receive audio signals from distant locations and decode them to display the corresponding text on the screen.
2. Usage tips
- Transmission and reception: In JT65 mode, each communication cycle is divided into 1 minute of transmission time and 1 minute of reception time. During the transmission time, you can enter the information you want to send, such as "CQ" for calling or the other party's call sign. Then, the software automatically encodes your information into an audio signal and transmits it through the transceiver. During the reception time, you need to carefully observe the spectrum graph of the software to find signals from afar. If you detect a signal, you can click on the signal to lock it, and then the software will automatically attempt to decode the signal.
- Decoding optimizationIf the signal is weak, try using the software's "Deep Search" feature. This allows decoding of information at lower signal levels, which can improve communication success rates.
IV. Antenna Construction: Building Your "Space Wings"
A rough estimate suggests that antennas may eventually be housed in dedicated compartments.
(1) Yagi antenna: The joy and challenge of building my own.
The "Bamu" antenna is one of the commonly used antenna types for EME (Earth-to-Moon) communication. It consists of multiple elements, and by adjusting the length and spacing of these elements, it can achieve high gain and a narrow beamwidth. Constructing a "Bamu" antenna requires some technical skill and patience, but the process is also enjoyable and rewarding.
Materials preparation
- Aluminum pipe: The length is calculated according to the design formula for creating a resonator.
- Insulator: Used to fix the oscillator, preventing signal loss.
- Coaxial cable: Used to connect the antenna and transceiver.
- Main beam: Used to support the oscillator, typically made of aluminum alloy tubes.
Steps for making
- Calculate the length of the oscillator.Based on the design formula for a Yagi antenna, calculate the lengths of the reflector, driven element, and amplifier. These lengths determine the antenna's operating frequency and performance.
- Constructing an oscillator: Use aluminum tubing to construct the oscillator, ensuring a secure connection. The length of the oscillator must be precise to guarantee the antenna's performance.
- Installing insulators: Install insulators on both ends of the oscillator to prevent signal loss due to transmission through metal components.
- Connecting feeder cableConnect the coaxial cable to the antenna's feed point. Keep the length of the feeder as short as possible to minimize signal loss.
- Testing and AdjustmentAfter completing the antenna fabrication, testing and adjustment are required. Use a spectrum analyzer or antenna analyzer to check the antenna's frequency response and gain. Based on the test results, adjust the length and spacing of the elements to optimize the antenna's performance.
(ii) Dishtype Antennas: The "Big Guns" of the High-Frequency Band
Parabolic antennas have higher gain and narrower beamwidths, making them suitable for EME communication in the high-frequency band. Although parabolic antennas are relatively complex to manufacture, their performance improvements are also significant.
Materials preparation
- Metal mesh: Typically used for disc manufacturing, usually made of aluminum mesh.
- Support frame: Used to support the disc surface, typically made of aluminum alloy or steel.
- Power supply: Used to transmit signals from the disc surface to the feed line.
Steps for making
- Manufacturing the disc face: Cut and bend the metal mesh according to the specified dimensions, forming a disc shape. The shape of the disc surface must be precise to ensure effective signal focusing.
- Install the support frame.Secure the disc to the support frame, ensuring that the disc's shape remains stable.
- Install the feed source: Install the feed at the focal point on the disc surface to transmit the signal from the disc surface to the feed line.
- Connecting feeder cableConnect the feeder cable to the feeder source to ensure stable signal transmission.
- Testing and AdjustmentAfter completing the manufacture of the dish-shaped antenna, testing and adjustment are required. Use a spectrum analyzer to check the antenna's frequency response and gain, and adjust the shape of the dish and the position of the feed based on the test results.
Recommended: Everyone can go to The website for DK7ZB Take a look; it includes a 14-element long boom Yagi antenna. Beginners can try to build this antenna, which is also a good way to develop practical skills.
Five. Communication steps: Talking with someone far away.
(1) Preparation
Before conducting an EME communication, it's essential to prepare thoroughly:
- Inspect the equipmentEnsure that all communication equipment, power amplifiers, pre-amplifiers, and antenna systems are functioning correctly.
- Calibration time: Use software such as Dimension4 to synchronize computer time, with an error of no more than 1 second.
- Test for background noise: Test the baseline noise level to ensure that the electromagnetic environment is suitable for EME communication. If the baseline noise is too high, try replacing the low-noise preamplifier or adjusting the antenna position.
(2) The communication process
- Select frequency: In the 2-meter band, 144.140 MHz is a commonly used EME frequency. Turn on your transceiver and tune it to 144.140 MHz, then open the WSJT software and select the JT65B mode.
- Transmission and reception：
- At the transmission time, enter the information you want to send, such as your call sign ("CQ") or the recipient's call sign. The software will then automatically encode this information into an audio signal and transmit it through the transceiver.
- When receiving, carefully observe the spectrum graph of the software to look for signals from distant locations. If you find a signal, you can click on it to lock it, and then the software will automatically attempt to decode the signal.
- Optimize communication：
- Based on the decoding results, adjust the antenna direction and power to optimize communication performance. If the signal is weak, try increasing the power or adjusting the antenna direction.
(3) Communication terminated
A successful EME (Earth-Moon-Earth) communication typically ends with the exchange of "73". This not only signifies the end of the conversation, but also serves as a friendly greeting to the distant friend. When you receive your friend's "73", respond in kind and then conclude this interstellar dialogue. Although the EME process may be brief, the sense of accomplishment and satisfaction will linger long after.
Six. Challenges and Rewards: The Sweet, Sour, and Bitter of Space Communication
(1) Challenge: The "roadblock" to space communication
The Moon's "temper"
The Moon is not a perfect reflector. Its surface is full of craters and uneven terrain, which cause signals to scatter and weaken. Furthermore, the Moon's orbit is not fixed; it is affected by Earth's gravity and the gravitational forces of other celestial bodies, causing the Moon's position and distance to constantly change. This means that when communicating with the Moon, we must always pay attention to its position and adjust the antenna's direction.
The "noise" of Earth.
The electromagnetic environment on Earth also poses significant challenges for EME communication. Urban electromagnetic noise, interference from industrial equipment, and even thunderstorms can all affect signal transmission. Before establishing EME communication, it is recommended to test the background noise level to ensure that the electromagnetic environment is suitable for EME communication. If the background noise is too high, you can try replacing a low-noise preamplifier or positioning the antenna in a quieter location.
The "test" of time
EME communication requires precise time synchronization. Since the signal needs to travel through space, the round-trip time is approximately 2.5 seconds, which means that we must strictly control the timing when transmitting and receiving. If there is even a slight deviation in the timing, it may result in the inability to correctly decode the signal. Therefore, it is necessary to carefully calibrate the computer's time before communication, ensuring synchronization with UTC time.
(ii) The "sweet fruit" of space communication
The "growth" of technology
Each attempt at EME communication represents a step forward in technology. You will learn how to optimize antenna patterns, how to adjust power amplifiers, and how to handle complex electromagnetic environments. The accumulation of these technologies will allow you to continuously grow in the field of radio communications.
The "emotional impact"
EME Communication is more than just a technical activity; it's also a form of emotional connection. Through radio waves, you can share your passions and dreams with friends far away. Even though you may be miles apart, the moon serves as a "bridge," connecting your hearts.
The "joy" of exploration.
EME Communication is an adventure in the unknown. Each communication feels like searching for a light in the darkness. You don't know if the signal will reach the moon, or if you will receive a response from the other party. But it's this uncertainty that makes each communication exciting and full of anticipation.
VII. Future Outlook: Intelligent EME Communication
As technology advances, future EME communication will become more intelligent. Features such as automatic antenna tracking, intelligent power control, and more efficient communication modes will make EME communication easier and more effective.
(1) Automatic antenna tracking
By using an electric rotator and a lunar tracking software (such as Z-Track), you can achieve automatic antenna tracking. This allows you to maintain optimal signal reception and transmission without manually adjusting the antenna's direction.
(ii) Intelligent power control
Future power amplifiers will feature intelligent power control, allowing them to automatically adjust power based on signal strength. This means you won't need to manually adjust the power, ensuring that your signal is always in optimal condition during transmission.
(iii) More efficient communication patterns
As technology advances, future communication patterns will be more efficient. For example, new encoding techniques will enable decoding at lower signal levels, further improving the success rate of EME (Enhanced Mobile Land) communications.
VIII. Summary
EME Communication is a journey full of challenges and rewards. It requires patience, skill, and enthusiasm, but each successful communication brings endless joy. I hope this guide will help you better understand the charm of EME Communication and embark on this wonderful radio adventure. Whether you are a radio enthusiast or an explorer with curiosity about the universe, EME Communication is a field worth exploring. May you find your own stars in the ocean of radio.
Epilogue
If you are not interested, you can stop reading here. Below are some of my personal thoughts and insights related to the content of this article, but they are limited.
Within the current radio community, radio is gradually shifting from an older demographic to a younger one. This has created a phenomenon where radio can regain its former glory. A large number of young people and teenagers have entered this community, injecting it with fresh, vibrant energy. However, due to their age or immaturity, they may sometimes exhibit behaviors that are difficult for us to understand. Although I am also a high school student, I have been involved in radio for many years. If you feel that I am biased towards one side, please feel free to point it out. Freedom of speech is important, but malicious attacks are not acceptable.
Based on the above, many people choose to ostracize or even use online harassment to target a specific person or group within the community, attempting to forcibly exclude them. While their actions may sometimes be difficult to accept, should we, as seniors, first provide them with the correct guidance? Are we destined to constantly lose fresh talent in this way? As the saying goes: "A piece of steel is still good steel if only it isn't rusted." I believe this applies here as well. When dealing with minors or young people, we should demonstrate more tolerance and openness, actively sharing our experiences within the community with them to help them grow quickly. Trust me, you will feel a great sense of accomplishment.
Okay, this is the last part. I wanted to thank everyone for reading this far. Because the original manuscript was quite disorganized, I used AI to help me tidy it up a bit, so that my thoughts would seem less chaotic and easier for beginners to understand. Did you notice any changes? Haha. Finally, this article is just an introductory guide for beginners. If there's a strong response to this article, I might create separate sections with detailed explanations to help beginners quickly overcome the initial challenges.
Finally, I extend my sincerest wishes to all the seniors and newcomers. I hope that we can all work together to make this radio community even more loving and supportive. I'm also creating a Q group for amateur radio enthusiasts, where everyone is welcome, including seniors and newcomers. In this group, there are no distinctions between members; it's simply a group of people who love technology and enjoy sharing their knowledge with others. If you don't fit that description, please don't join the group. We aim to create a positive and supportive community atmosphere.
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