EME (moonbounce) skeds: moon windows, Q65, Doppler and what to agree

Updated 2026-10-27 · SQ3SWG

In EME, or moonbounce, both stations point their antennas at the Moon and use it as a passive reflector. The path is about 770,000 km long, so signals are very weak, but any two stations that can see the Moon at the same time can make a contact – across continents, on 2 m, 70 cm, 23 cm and higher.

The moon window

The Moon has to be above the horizon for both stations at the same time, ideally well above it and away from local obstructions. Planning software or WSJT-X's astronomical data shows the common window. A sked is only possible inside it.

Mode and period

Most digital EME today uses Q65 in WSJT-X, with 60-second periods on the lower bands (Q65-60A is common on 2 m); CW is still used by larger stations. Agree the exact mode and submode, the frequency, and who transmits in the first period.

Doppler and frequency

The Moon moves relative to both stations, which shifts the frequency – a few hundred Hz on 2 m, more on the higher bands. WSJT-X can correct for it; agree how you will handle it (both correct, or one station sets a fixed frequency) so you meet on the same frequency.

Completing the contact

A complete EME contact exchanges both callsigns, reports (in Q65 these are signal reports in dB) and a confirmation. Give it time: an hour is normal, and a long period of nothing is common before the first decode.

Use the band room to find partners and the chat's sked proposal to fix the time; put mode, frequency, who transmits first and the moon window in the note.