An open-source 240-antenna array to bounce signals off the Moon
moonrf.comI don't think you should call something 'open source' until you've released the source, but other than that this is an extremely impressive project. HAM's have been doing EME since forever (https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Ear... ), it is a very neat trick.
It almost looks as if the EME bounce capability of this antenna is a fig leaf or an afterthought, my own 'applications' list would be a lot of things, but not that.
Apparently it’s a way to attract attention and support. I’ve been following picoIDE which got some attention here on HN 4 months ago [1]. When asked then where the src is, the answer was in a few weeks. Fast-forward a crowd-supply campaign (no mention 4 months ago) to the tune of 350k and the repo is still empty.
It's open source. Here is the GitHub: https://github.com/open-space-sdr/main
Have you actually looked in that repo? No hardware source and a few things related to sdr or fpga but nothing that allows someone to build this.
You can find all the software there (for every demo shown on the website), but it's not "build-ready" given the hardware isn't released yet as the website makes clear. The repo is from last year but not generally advertised.
I suppose HN picked up on this project again because of the moon mission this week.
It was discussed a few months ago: https://news.ycombinator.com/item?id=45790672
I think mrtnmcc put up that repo as a response to my comment. And you're right there is no way to build it from what's posted.
Repo has been there, but I pushed an update for the latest demos, thanks for the reminder :)
You have to understand this is a relatively sleepy personal project at this point still.
That wasn't there when I wrote that comment.
found it at the very bottom of the updates page
That wasn't there either. See archive...
the open-source licenses are listed at https://moonrf.com/updates/#faq
Wild hardware flex for a garage project. Reverse-engineering the Pi 5's MIPI to push 5.6 Gbps from custom MASH sigma-delta ADCs to a Lattice ECP5 FPGA to the Raspberry Pi is serious engineering. The idea that the RF receiver looks like a "camera" to the Pi while the transmitter is a "display" is super creative. Getting a 1.5 kW, 240-antenna EME array for $2,499 is actually cheap for something like this.
Their standalone 4-antenna tiles (https://moonrf.com/updates/) show off some killer apps, like 30 fps spatial RF visualization and NEON-optimized drone video interception.
I'm rolling my eyes at the "Agentic Transceiver" part, though. It is highly doubtful that an onboard AI casually writes, debugs, and compiles a real-time C app with analog video color sync recovery and decode in ten minutes.
> Reverse-engineering the Pi 5's MIPI to push 5.6 Gbps from custom MASH sigma-delta ADCs to a Lattice ECP5 FPGA to the Raspberry Pi is serious engineering
Using video interfaces to transfer arbitrary data at high speeds is becoming a common trick for cheap boards with limited interfaces. Video inputs and outputs are generally highly mature and optimized to avoid dropping frames because everyone wants reliable video. Putting arbitrary data into video IO pipelines is a cheap way to get high speed IO through standard interfaces.
There is a cool project that uses cheap HDMI to USB capture devices for high speed data transfer out of cheap FPGA boards that have HDMI output [ https://github.com/steve-m/hsdaoh ]
In a perfect world, using PCIe directly would be a much better solution for a project like this. Having access to PCIe DMA support directly without relying on video IO peripherals is helpful for high speed ADC/DAC applications like this. It would also make the board more portable to other SBCs.
The ECP5-5G can do PCIe 2.0 x2 or PCIe 1.0 x4 which would provide around 8Gbps of data transfer. The problem is that the Raspberry Pi 5 only exposes a single PCIe lane to the user. The other 4 PCIe lanes of the Raspberry Pi 5 SoC are routed to the RP1 chip, which has the MIPI and CSI interfaces that are used in this project. So the data is going through a convoluted path instead of being connected to PCIe directly.
I would have to look at the details more closely, but even using the PCIe 2.0 x1 port (around 4 Gbps after overhead) on the Raspberry Pi would be close in bandwidth to the 5.6 Gbps number they give for their custom MIPI solution.
I think the Raspberry Pi 5 is a good first choice for most projects because it is widely support and has the largest community, but for a project like this the benefits of moving to a different SBC with PCIe 2.0 x2 would have been helpful. Keeping the project semi-independent of the SBC has a lot of benefits.
> Using video interfaces to transfer arbitrary data at high speeds is becoming a common trick for cheap boards with limited interfaces.
There is a line in the book Accelerando about how evolution did this with biological vision.
It's basically the highest bandwidth sense we have and evolved AFTER smell (chemical based) and auditory (gas pressure based) senses.
unfortunately the ECP5-5G FPGA (with the SERDES/PCIe option), costs way more than the ECP5 (without SERDES). The Pi-5's MIPI interfaces gives you 8 parallel LVDS lanes that can run at 640 MHz each which is manageable for a cheap FPGA.
While true I do worry that it's mandating a pi 5 for each tile? And who knows how specific it is to the 5. Doesn't seem very open relative to something like a usb superspeed, pcie, or 10gbe. USB could be maybe done with the LIFC-33U depending on I/O limitations. PCIe can be done on various FPGAs in the lattice lineup and others.
If you use PCIe, theoretically you don't need to reverse engineer how they implemented because you're not at the edge of the spec like they are here.
That said, I've thought about doing what they're doing countless times and it is nice to see it would work.
> While true I do worry that it's mandating a pi 5 for each tile? And who knows how specific it is to the 5.
In the multi-tile array it apparently still only needs one Pi [1] as the FPGAs do the heavy lifting.
correct, one Pi-5 for the MoonRF. The beamforming computation is done digitally "on the fly" in round-robin across the sixty QuadRF boards.
I'm struggling to understand the signal chain or antenna architecture here. If those two MAX chips are 2829s this would be 2x2 mimo per tile but I'm not super familiar with that product line and the PCB layout looks like a 4x4 setup.
And yeah, the agentic stuff is dumb, I've played a ton with doing low level SDR work on Opus 4.6 and it's truly ass.
Also, the "can't radar, plz don't ITAR" is horseshit. Some basic fw tweaks and you could get this to be, at the very least, a sweet FMCW setup.
MAX2850/2851 4x4. Also, large radar stuff is more nuanced than "just some fw tweaks" as you claim. Same as Facebook is not just some PHP scripts...
I used to work radar systems. The point being that the hardware is fully capable. The software side is quite well understood at this point. There will be plenty of repos floating around in a year to turn this into an airborne drone SAR or whatever. Functional range resolution will be around 4m but that's plenty for most shenanigans.
At a functional range resolution of 4M would it even qualify as violating ITAR even if it was tweaked to do so?
> Also, the "can't radar, plz don't ITAR" is horseshit.
My assumption is that they're trying to avoid crossing a legal line, as opposed to being personally invested in the idea of preventing radar use by a determined hobbyist.
ITAR feels a lot like Bernstein v. US all over again. Until very recently, everyone who can do anything that would be covered by ITAR was a giant corporation that likes the moat that regulations create, so it's unthinkable to challenge it. But that is changing, just like cryptography was in the early 90s.
RTL-SDR-grade fleet doing passive radar (using radio/TV OTA broadcasts) isn't actually that new; but pretty much any detailed reports have caught self-censoring after TLA visitors came by.
> Getting a 1.5 kW, 240-antenna EME array
It says 1W TX power per antenna. So the 240 antenna array which draws 1500W has a transmit power of 240W.
EIRP. There's some gain involved.
I think they're claiming the actual transmit power is 240W (23.8 dBW), and the EIRP is 63.1 dBW.
I am sort of skeptical of the claimed gain... even at 6GHz, you need a 2-meter parabolic reflector to get 40dB, the array is 1/10th that diameter. EDIT: Ignore this second paragraph I misread the spec page.
The MoonRF array is a full 1 meter diameter as shown on the page
I'm asleep and I misread that as 10cm. Thanks.
For context, the same phased-array transceiver technology is used in Starlink terminals, some of which have 1,280 active elements. Such a terminal can require as much as 150W to function.
It's also why pictures of modern naval vessels show flat panels instead of rotating parabolic antennas as in past decades. The panels contain advanced phased-array radars.
Every time I hear about Earth-Moon-Earth moonbounce comms, I think of this classic reddit comment: https://www.reddit.com/r/amateurradio/comments/8lpk45/commen...
Yeah, this stuff goes way back. My great-great-uncle Adelmo Landini, who had worked with Marconi, was already doing it (I think there used to be a patent somewhere).
phased array is better than whatever that guy was doing!
MoonRF mostly takes care of the hardware and pointing, and then the fun is playing with software and signal processing: https://github.com/open-space-sdr/main
That post is truly hilarious though. If everyone talked like that on the nets, the hobby would surely grow a lot faster.
:DDD
Pretty cool. And expensive. It's pretty amazing how starlink sells basically this for $200. Pretty sure they subsidize it.
Ps you don't really need this. A phased array is great for communicating with or tracking fast moving objects. For something as slow as the moon a simple parabolic dish, either manually aimed or with an az/el motor will be more cost-effective. Motors get expensive too with wind and rain and longevity (moving around 24/7) but hams don't moonbounce constantly.
Starlink sats move really quickly through the night sky and it tracks multiple so you don't have interruptions this is why for that purpose a phased array is great. For incidental ham use to the moon it's very interesting tech but not exactly necessary.
Well this is roughly 2 thousand times higher power than a Starlink user terminal.
Aand of course it's open source, https://github.com/open-space-sdr/main/
Is starlink that low power? The whole array of this one is 1.5kW. I thought starlink would be at least a few watts especially considering its bandwidth.
Yeah it's impressive and I know hams often spend a lot of money on gear. I don't though (I don't even do HF) but it's certainly cool to see.
But for incidental moon tracking I don't really see the need for a phased array other than the cool factor and the knowledge gained building it. Which are perfectly good reasons to do it of course! Just not technical ones.
EME has been made a bit more affordable and effective by weak signal modes and DSP.
It used to require very high power, expensive transmission lines, preamps and monstrous arrays of Yagis. Now with JT65x, and SDRs, you can use cheaper coax to get transmit power to the antenna eating that loss with more RF, and put SDRs for RX at the array. People running digital modes are getting away with needing less gain.
5650MHz is the only place to do it with this thing. Might want to break out a calculator before the credit card because path loss has to be more than 285dB. But if you can swing it, might want to buy two so you have someone to talk to. I have not heard anyone using 5650.
> The target launch price is probably ~$399 (dependent on the tariff landscape over the next month). For that you get the QuadRF tile, an included Raspberry Pi 5, the custom case, tripod, USB-C power supply, cables, and a pre-loaded SD card with a ton of cool SDR applications.
Meanwhile... the RPi alone will probably make up 299 dollars of that price tag [1].
It is not a good time to design hardware that needs RAM. Arrest and imprison Sam Altman.
[1] https://www.jeffgeerling.com/blog/2026/dram-pricing-is-killi...
The 1 GB RPi-5 is only $45 still, hopefully it stays that way :)
> Power Supply: 12 V DC (≈1.5 kW peak)
That's a lot of juice for 12VDC
>> Power Supply: 12 V DC (≈1.5 kW peak)
> That's a lot of juice for 12VDC
Indeed it is. It's 125 amps, which apart from car starting motors is essentially unheard of because of wiring losses. I think the article somehow got this wrong.
At these power levels, rational designs raise the source voltage, then down-convert closer to the loads.
There are PC style PSUs rated to up to 1.2kW for 110V and 2kW-ish for 220V outlets for use with crypto mining machines. They are available used way below kW rating for having little values outside of narrow relevant contexts
This is brilliant, but on a less than brilliant internet connection like mine the site images are loading at a snails pace. Maybe use WebP rather than png?
Looks interesting, I have many great ideas to test them out with this! I wonder if I can use my SDR with it.
It says it’s open source but I can’t find a link to a repository. Am I missing something?
Solid work. The edge cases in section 2 are the ones that always bite you.
Cool, how full array compares to the single antenna placed on Starlink satellite ?
How would that be a useful comparison? Aren't the use-cases too different?
Not only is the moon >100x farther away (even accounting for near-horizon satellite angles), but you're also trying to bounce a signal off it as a passive reflector, which is harder than just transmitting something an active lunar receiver could detect and re-transmit back.
If starlink were anywhere close to as far away as the moon, you would have a comparable antenna size. That's like bragging about how compact your zoom lens us while your buddy trying to get photos of the Martian canals.
"Country restrictions apply". Which countries?
Each country has different regulations for amateur radio bands. In Germany for example, in the bands > 2 GHz maximum power is capped at 75W PEP [1], the US has vastly different limits [2]
[1] https://www.gesetze-im-internet.de/afuv_2005/anlage_1.html
[2] https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D...
I'm sorry, I thought it was very obvious that I was talking about ITAR export controls, not about destination country domestic regulation.
This is a clue from their webpage: "Not intended for radar applications. Core functionality needed for radar not included due to export control restrictions."
All I guess? If you're licensed you should know what you can and can't do.
No, amateur radio does not cover ITAR.
Which is why I ask. I'm not a lawyer, but there could be a general dual use ban, but with some other regulation that exempts e.g. UK.
Any that forbid or restrict satellite comms?
Don’t use this in Iran.
I'm pretty sure the "country restrictions" are about ITAR, not the destination country regulation.
When the page says "uh… do not use this to build a phased array radar… even though you could. And if you do, then in no way were we involved. Just don't", this is extremely likely to be about ITAR.
> License: Amateur Radio (Technician+) to operate, country restrictions apply.
This implies it's about operating a radio transmitter.
Iran will absolutely frown on that right now, as they've frowned on Starlink. Their internet shutoff indicates "empowering the public to connect across the world" is not really what they want.
Leaving Iran and DPRK aside, the frequency range, power levels, and everything else depends of course on the operating country.
> Amateur Radio (Technician+) to operate
This is not even true. You can operate within the ISM band without a license, with ISM band limits. So this is what I mean; listing "country restrictions" (not "local restrictions") doesn't make any sense in this context. Everything is always subject to local laws always. Obviously. And that's not even mentioning that a large reason for having this device is receive-only, which definitely doesn't require a license in the US.
~5.8GHz is an ISM band world wide.
Yes, transmitting at "amateur radio power" or within amateur radio bands but outside ISM requires something.
But "country restrictions apply" doesn't make sense if it means that. That'd be like selling condoms and referring to vatican banning them (I don't know if they do), or some countries banning gay sex, so country restriction applies if you use it for gay sex.
can amateurs bounce photons off the mirrors left there by Apollo 17 yet
or does it still need industrial grade lasers?
Getting industrial grade lasers is the easy part.. it seems to be within range of aliexpress available tattoo removal laser (based on the laser pulse energies listed in https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment... and rough laser tattoo removal energies listed in https://pmc.ncbi.nlm.nih.gov/articles/PMC10421900/ .. take aliexpress rating with grain of salt)
You do need access to a large telescope (at least 1.2m based on the wiki article), a sensitive detector (is photomultiplier tube sensitive enough??) and most importantly, access to your local laser clearinghouse so you don't accidentally shoot an airplane, blind the pilot and got arrested, or a satellite and start a war (if you believe some guy on quora). Probably the last part is the hardest thing for an amateur