ARRL EME Contest: Weekends, Grid Exchange and Moonbounce Logging

Bouncing a signal off the Moon and back is still one of the most dramatic things an amateur can do, and one contest is built entirely around it. The ARRL EME Contest invites stations to work as many others as possible via the Earth-Moon-Earth path on any authorized amateur frequency above 50 MHz. This guide summarizes the official ARRL page: the dates of the four weekends, the exchange and how it doubles as the multiplier, how to log contacts correctly, the deadline, and some practical advice from the WSJT-X documentation on submodes for each band. The third weekend of the 2026 event starts today, so the timing is good for anyone curious about listening.

What the Contest Is

The ARRL EME Contest page gives the objective as working as many amateur stations as possible via the Earth-Moon-Earth path on any authorized amateur frequency above 50 MHz. The contest exchange is a station’s four-digit Maidenhead grid square locator, and the grid square also serves as the score multiplier. Analog stations, such as CW operators, may optionally send a signal report in any mutually understood format if station size or propagation prohibits exchanging grid squares.

That last sentence says a lot about the nature of the activity. On the Moon path, signals are extremely weak and fade rapidly, so some stations, especially small ones, cannot complete a full exchange on every contact. If you are new to the whole idea, our EME moonbounce guide for beginners explains how the path works and what equipment people use. For the physics, the Wikipedia article on Earth-Moon-Earth communication is a good reference.

The Four Weekends

The contest is organized as four full weekend periods, each running 48 hours from 0000 UTC on Saturday through 2359 UTC on Sunday. The weekends are split by band group, so you work the weekends that match your equipment. The ARRL lists these dates for 2026:

The split exists because moonbounce conditions differ by band group. Microwave stations tend to be small and need the Moon at a good position, while the lower bands need large arrays and operate at times when the Moon’s declination and distance suit them. Planning a weekend means checking the Moon’s rise and set at your location and the times when the Moon is closest to Earth, since a nearer Moon gives a slightly stronger echo. WSJT-X includes an astronomical data window for exactly this purpose.

Grid Squares as the Exchange and the Multiplier

In most contests the multiplier is a country or a zone. Here it is the grid square, which rewards variety of locations around the world. To make the scoring work, your log must record the four-digit grid from which you made the QSO and the four-digit grid of the station you contacted, in the sent and received information of every QSO line, regardless of what was actually sent over the air. If you need a refresher on locators, read our guide to grid squares and the Maidenhead system.

Portable stations deserve special attention. The ARRL gives examples of a station that operates from its home grid on one day and from another grid on the next, and then returns home for the November weekend. Each QSO line carries the grid that was used at that moment, so the checker credits the right multipliers. If you plan to operate from a rare grid, treat that as a selling point to announce in advance, because other stations will want the new multiplier.

Choosing a Mode and Submode

The contest allows any mode. In practice, digital modes dominate on most bands, with CW and SSB used by large stations. The WSJT-X User Guide describes how digital EME has evolved: until the arrival of Q65, it was mostly done with JT65A on 50 MHz, JT65B on 144 and 432 MHz and JT65C on 1296 MHz, with JT65C, wider JT4 submodes or QRA64 on the microwave bands. The guide now recommends a suitable submode of Q65, which has replaced QRA64, for EME on any VHF or higher band, and gives these examples:

• 50 and 144 MHz: Q65-60A.
• 432 MHz: Q65-60B.
• 1296 MHz and 2.3 GHz: Q65-60C.
• 3.4 and 5.7 GHz: Q65-60D.
• 10 GHz: Q65-60D or E.
• 24 GHz and higher: Q65-60E.

The pattern is the one you would expect: higher bands bring larger Doppler spread, so the tone spacing grows from A to E. The guide also notes that JT4, JT65 and Q65 offer message averaging, which sums successive transmissions that carry the same message and allows decodes several decibels below the threshold for a single transmission. JT65 and Q65 also offer a priori decoding that uses information accumulated during a QSO. All of these options are selected from the Decode menu. For further background on the mode, see the WSJT-X User Guide.

Doppler, Offsets and Echo Mode

Doppler shift is a major factor in moonbounce, particularly on the microwave bands. With a CAT-controlled radio, WSJT-X can compensate for changing Doppler shift, even during a CW EME QSO. The guide explains how: put the radio in CW mode, set the mode option in the Radio settings to None so that the program does not try to change it, and use the Tune button to switch between receive and transmit. No tones are transmitted, because the radio is in CW, but the program knows when you are transmitting and adjusts the dial frequency for each state.

WSJT-X 3.0 also supports large offsets between receive and transmit frequencies, for example to allow EME QSOs between countries that have amateur allocations at 2304 and 2320 MHz. In the guide’s example, a station receives on 1296 MHz and transmits on 1298 MHz using a transmit shift of +2 MHz. Finally, Echo mode lets you hear your own echo and measure it. The Echo transmission is a fixed 1500 Hz tone lasting 2.048 seconds, and the program records the lunar echo about 2.5 seconds later, computes its spectrum and displays it. Each cycle takes 6 seconds. It is a very good way to test your station before you try a contact, because if you cannot hear your own echo, the other stations will not hear you either.

Why EME Signals Are So Weak

The Moon is roughly 384,000 kilometers away, and its surface reflects only a small fraction of the energy that reaches it, scattering the rest in all directions. The total path loss for a round trip at 144 MHz is on the order of 250 dB, which is why moonbounce stations use large antenna arrays, low-noise preamplifiers and, on the lower bands, high power. The path loss grows with frequency, which is partly why the microwave weekends are separate: stations on 10 GHz use dish antennas and have to deal with high pointing accuracy and large Doppler shift, while stations on 50 MHz need very large arrays of long-boom Yagis because the wavelength is long.

The echo is also affected by libration fading, the slow rocking of the Moon as seen from Earth, which makes the reflected signal flutter, and by Faraday rotation on the lower bands, which changes the polarization of the signal as it passes through the ionosphere. These effects explain why careful stations use circular or switchable polarization and why the Q65 submodes have wider tone spacing at higher frequencies. You do not have to master the theory to operate, but knowing why a signal comes and goes helps you decide whether to keep calling or wait for a better moment.

Operating Practice and Etiquette on the Moon Path

EME operating practice is different from that on HF. Because contacts are slow and signals weak, most operators agree schedules in advance, often on a chat page that lists who is calling, on which band and when. The conventional calling period structure is that one station transmits in the first period and the other in the second, switching according to the odd and even minutes or the agreed sequence length, so both stations must be accurately timed. Do not call on top of an active QSO, and do not transmit continuously when you are not in a scheduled contact: the bands are quiet and each period is valuable.

Contest weekends bring out stations that are rarely heard at other times. If you are a beginner with a modest station, listen to find the large stations, and when you do call, send clean, correctly timed messages. Keep your total power within the limits of your licence and make sure you do not cause interference to terrestrial weak-signal operators nearby. If you have a good local VHF community, ask for a skilled operator to help you with a first test, because a first echo is much easier with a guide. The skills you learn there carry over to every other weak-signal mode.

Logging and Log Submission

The ARRL says that logs are due no later than 30 days after the final weekend of the contest ends at 2359 UTC. Logs must be submitted through the ARRL web app, and only online submission is accepted. Submissions must contain your complete log from all weekends you operated. If your logging software exports an ADIF or Cabrillo file with the required fields, including WSJT-X, you can submit it directly. For Cabrillo conversion help the ARRL points to a conversion tool, and certificates are available for download online.

The ARRL lists the ADIF fields that must be present. These fields are exported automatically by WSJT-X. If you use another ADIF-compliant program, the following are recommended:

• call: the call of the station worked (required).
• gridsquare: the grid of the station worked (optional, because it is determined during log checking).
• mode and submode: such as FT8, CW, SSB or MSK (mode is required).
• rst_sent and rst_rcvd: signal reports (optional).
• time_on or time_off, and qso_date or qso_date_off: the time and date of the QSO, with the end time preferred (required).
• band and freq: for example 2M, 70CM, 23cm or 3cm, and the frequency in MHz (both required).
• station_callsign and my_gridsquare: your callsign and your own grid square (required).

Missing fields cause rejected logs, so test your export before the weekend by making a dummy log entry and reading the resulting file.

Getting Ready as a Beginner

Most stations in the contest have large antenna arrays, but many people take part as listeners or with modest setups on 6 meters. Our 6 meter band guide explains the band where small EME stations most often begin. The 2 meter band guide and 70 cm band guide cover the layout of the bands where many serious EME stations operate.

1. Listen first. Set WSJT-X to Q65 with the submode listed above for your band and watch for decodes on the contest weekends.
2. Check your clock and your Doppler setup with Echo mode before the Moon is high.
3. Prepare a log with the correct fields, including your own grid.
4. Arrange schedules with other stations. Many EME contacts are made by agreement in advance using chat groups.
5. Be patient. Contacts take a long time, and the Moon is only above the horizon for part of each day.

The Bottom Line

The ARRL EME Contest runs over four 48-hour weekends, two for 2.3 GHz and up and two for 50 to 1296 MHz, and uses the four-digit grid square as both exchange and multiplier. Use the Q65 submode recommended for your band, let WSJT-X handle Doppler, test with Echo mode, record both grids on every QSO and submit a complete ADIF or Cabrillo log within 30 days of the last weekend. Even if you only listen this time, you will learn what a real moonbounce signal looks like.

Frequently Asked Questions

What is the exchange in the ARRL EME Contest?

Each station’s four-digit Maidenhead grid square locator, which is also the multiplier. Analog stations may optionally send a signal report if grid squares cannot be exchanged.

When are the 2026 weekends?

August 8-9 and September 5-6 for 2.3 GHz and up, and October 31 to November 1 and November 28-29 for 50 to 1296 MHz.

Which frequencies can I use?

Any authorized amateur frequency above 50 MHz.

Which WSJT-X mode should I use?

The WSJT-X guide recommends a suitable Q65 submode for EME on any VHF or higher band, for example Q65-60A on 50 and 144 MHz and Q65-60B on 432 MHz.

How do I submit my log?

Through the ARRL web app, as a Cabrillo or ADIF file containing all weekends you operated, no later than 30 days after the final weekend ends.

Do I need a huge station?

Big arrays help, but the contest allows any mode, and the page notes that analog stations may skip the grid exchange when station size or propagation prohibits it.