The Moon Loop.
Tonight is the fifteenth of the eighth lunar month. For most of the world the full moon is a lantern; for a radio amateur it is also the oldest reflector in the sky. This is a short holiday post: a little moonbounce, what the station is doing tonight, and a greeting to every station in the footprint.
Mid-Autumn Festival is the one night of the year when an entire civilization looks at the same object in the sky at the same time. Radio amateurs have a private version of that habit: the moon is not only something to look at, it is something to transmit at. The round trip is about two and a half seconds at the speed of light, and the signal comes back roughly 250 dB weaker — your own voice, returned to you a quarter-million miles older. Tonight, between mooncakes, this post walks the shortest possible path through the oldest link in radio, checks in on the station's night shift, and closes with a greeting. The loops are on watch; the human is at the table.
TL;DR — the festival in four findings
- FactMoonbounce is real, and older than the transistor radio. Amateurs first heard their own echoes return from the moon in 1953 and completed the first two-way EME QSO in 1960. The round trip takes ~2.5 seconds; the path loss at 144 MHz is about 250 dB.
- FactThe station works the night shift. MRRC-FT8 keeps decoding FT8 on the FT-710 through the night — live demo — while the EFHW auto-tuner stands outside under the same moon, holding the match near 1:1.
- ThesisThe loops exist for evenings like this. Cron triage, the FDE board, and the test-gated implementer keep the night watch unchanged, because the point of agentic engineering is that judgment stays human while the human is allowed to go eat mooncakes.
- Analogy海上生明月，天涯共此时 is a link budget in disguise. One luminous source, every receiver in the footprint, sharing the hour — written twelve centuries before radio, and still the cleanest description of what propagation does.
The oldest link in radio
Every civilization has aimed a transmitter at this one satellite.
Earth-Moon-Earth — moonbounce, EME — is exactly what it sounds like: you aim a directional antenna at the moon, transmit, and listen for the echo off a rocky sphere 384,400 km away. The moon reflects only a few percent of what hits it, and the path loss at 144 MHz runs around 250 dB, so what returns is a whisper of a whisper. Yet it returns. Radio amateurs first heard their own signals come back from the moon in 1953, and completed the first two-way moonbounce QSO in 1960 — years before most households owned a transistor radio. Since then EME has been the summit of weak-signal operating, and digital modes designed for deep noise dragged it within reach of modest stations.
There is a peculiar pleasure in it that no other contact offers: you can hear your own signal come home. Key the transmitter, wait two and a half seconds, and there you are — a quarter-million miles of travel, older. No ionosphere to thank, no repeater operator, no satellite transponder with an owner and a schedule. Just you, physics, and the one reflector every human being on the night side of Earth can see at once.
海上生明月，天涯共此时。
Over the sea the bright moon rises; at the far edge of the sky, we share this very hour. trans.
Zhang Jiuling, Gazing at the Moon, Thinking of One Afar (Tang dynasty, 8th c.)
Zhang Jiuling wrote that line twelve centuries before Marconi, and it remains the cleanest one-sentence description of propagation ever composed: a single luminous source, and every receiver in the footprint sharing the hour. Radio only made the sharing two-way. For a ham, 天涯共此时 is not a metaphor — it is a coverage map. If the moon is in your sky and in mine tonight, then there is a path between us. It costs about 250 dB, and it has been toll-free for four billion years.
The moon is the only relay no authority allocated and no operator maintains: no coordination council, no license condition, no subscription — and its downtime schedule (phase, libration, perigee) is published in the oldest calendar humanity keeps. Every other way to reach over the horizon is infrastructure. This one is landscape.
Five projects on festival duty
The night shift does not eat mooncakes; it eats 15-second slots.
Mid-Autumn is a family festival, and the station knows it. Tonight the VLSC projects run their ordinary watch with a slightly ceremonial roster:
| Project | Day job | Festival duty tonight |
|---|---|---|
| MRRC | Universal HF remote via Hamlib/rigctld | Keeps the HF rig reachable from the dinner table — the radio stays in the shack, the operator doesn't have to. |
| MRRC Modern | USB-native remote for FT-710 / IC-7300 | Drives the desk rig: spectrum and audio over the one cable, waterfall steady as moonlight. |
| SunMRRC | SunSDR2 DX server, IQ demod + FFT | Tonight its 512-bin waterfall is what it always secretly was: a dark sea with the moon on it. |
| EFHW | ESP32-S3 servo-driven Fuchs auto-tuner | Stands outside in the autumn air, bias-tee powered, holding the match near 1:1 under the full moon. |
| MRRC-FT8 | Headless FT8/FT4 server, WSJT-X Improved core | The night shift proper: UTC slot discipline all night, logging QSOs while the household sleeps — watch it live. |
If you want a small festival experiment of your own: FT8 on a clear festival night is its own kind of moon-viewing. Open the waterfall, watch the 15-second slots light up from three continents, and remember that every one of those traces is somebody else's station, somebody else's evening, somebody else looking at the same sky between transmissions.
明月几时有？把酒问青天。
When did the bright moon first appear? Cup in hand, I ask the blue sky. trans.
Su Shi, Prelude to Water Melody (1076)
Su Shi keyed that transmitter exactly once, in 1076, and the echo is still arriving — nine and a half centuries of replies, one per Mid-Autumn, from every reader who ever looked up after hearing it. It remains the oldest recorded CQ addressed to the sky, and unlike most CQs, this one has never once gone unanswered.
The loops don't take the evening off — that's the point
Agentic engineering, demonstrated by a festival.
This site has written at length about loops — the inner loop of contract tests, the support loop that turns field symptoms into shipped fixes, the board where classification is the decision. Tonight is what they are all for. While the family eats mooncakes, the cron still fetches diagnostic bundles every ten minutes; the first reading still lands classified on the FDE board; the unattended implementer still proposes test-gated patches on isolated branches while main sleeps; and the PTT gate still refuses to let any automation touch a transmitting radio. Nothing about the festival changes the cadence. The unchanged cadence is the festival gift.
The division of labor on the thesis page — agents carry execution, humans carry intent, boundaries and judgment — is usually argued in the language of throughput and evidence. But its real payoff is quieter: on the one night of the year set aside for looking at the sky, the human can look at the sky. Judgment stays on call; the night watch doesn't have to.
A loop that cannot run unattended on a festival night is not a loop; it is a chore with a cron expression. The measure of the automation is not how much it does while you watch — it is that the evening exists at all: instruments on both ends, verdicts human, and the operator at the table instead of at the console.
The Coda said that every loop is a prayer with a reply. Tonight the reply is overhead: one reflector, a quarter-million miles out, round trip two and a half seconds at the speed of light — and somewhat longer at the speed of family, which is the correct speed for a holiday.
A greeting to every station in the footprint
CQ CQ CQ de BG1SB — Mid-Autumn greetings, all bands, all modes.
To every reader of this blog, every operator running MRRC, MRRC Modern, SunMRRC, EFHW or MRRC-FT8, every friend in the WeChat group, and every station that has ever answered a CQ from this QTH: Happy Mid-Autumn Festival. May your SWR sit at 1:1 and your mooncakes be sweet. May your noise floor drop with the evening temperature. May the DX answer your first call, your finals stay cool, your batteries stay full, and your QSL cards arrive promptly. And if you call into the dark tonight, may something answer — even if it is only your own echo, returned two and a half seconds older, having touched the moon.
但愿人长久，千里共婵娟。
May we live long, sharing this fair moon though a thousand miles apart. trans.
Su Shi, Prelude to Water Melody (1076)
The last line of Su Shi's poem is the whole of this post: longevity is a wish, but the shared moon is a fact — re-measured every year, by everyone with eyes, and by everyone with a receiver. From the desk rig, the rack server, the tuner in the yard, and the loops that keep watch over all of them: 中秋快乐，阖家团圆。73 & 88 de BG1SB.