[HN Gopher] An open-source 240-antenna array to bounce signals o...
___________________________________________________________________
An open-source 240-antenna array to bounce signals off the Moon
Author : hillcrestenigma
Score : 242 points
Date : 2026-04-06 03:22 UTC (19 hours ago)
(HTM) web link (moonrf.com)
(TXT) w3m dump (moonrf.com)
| infinitewars wrote:
| 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.
| HNisCIS wrote:
| 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.
| jowelene wrote:
| 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...
| HNisCIS wrote:
| 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.
| natpalmer1776 wrote:
| At a functional range resolution of 4M would it even
| qualify as violating ITAR even if it was tweaked to do
| so?
| blincoln wrote:
| > 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.
| jrockway wrote:
| 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.
| jcalvinowens wrote:
| > 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.
| HNisCIS wrote:
| EIRP. There's some gain involved.
| jcalvinowens wrote:
| 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.
| mrtnmcc wrote:
| The MoonRF array is a full 1 meter diameter as shown on
| the page
| jcalvinowens wrote:
| I'm asleep and I misread that as 10cm. Thanks.
| Neywiny wrote:
| 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.
| mschuster91 wrote:
| > 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.
|
| [1] https://moonrf.com/updates/
| mrtnmcc wrote:
| correct, one Pi-5 for the MoonRF. The beamforming
| computation is done digitally "on the fly" in round-robin
| across the sixty QuadRF boards.
| tomstokes wrote:
| > 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.
| mrtnmcc wrote:
| 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.
| alexpotato wrote:
| > 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.
| diimdeep wrote:
| Cool, how full array compares to the single antenna placed on
| Starlink satellite ?
| Terr_ wrote:
| 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.
| b00ty4breakfast wrote:
| 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.
| drmpeg wrote:
| Previous post.
|
| https://news.ycombinator.com/item?id=45790672
| infinitewars wrote:
| looks like there have been updates since then:
| https://moonrf.com/updates/
| mschuster91 wrote:
| > 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...
| mrtnmcc wrote:
| The 1 GB RPi-5 is only $45 still, hopefully it stays that way
| :)
| thomashabets2 wrote:
| "Country restrictions apply". Which countries?
| ceejayoz wrote:
| Any that forbid or restrict satellite comms?
|
| Don't use this in Iran.
| thomashabets2 wrote:
| 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.
| ceejayoz wrote:
| > 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.
| Levitating wrote:
| All I guess? If you're licensed you should know what you can
| and can't do.
| thomashabets2 wrote:
| 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.
| mschuster91 wrote:
| 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...
| thomashabets2 wrote:
| 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."
| manuelmenzella wrote:
| It says it's open source but I can't find a link to a repository.
| Am I missing something?
| xkbear89 wrote:
| You are not missing it -- it does not seem to be published yet.
| The site says open source but from the updates page it looks
| like the hardware design files and SDR software will ship
| alongside the physical product when it launches. This is pretty
| common with open-source hardware projects: the design is open
| but the repo appears after the first production run, partly
| because the schematics and firmware are still being iterated on
| and partly because publishing incomplete designs invites issues
| before the team is ready to support them.
|
| What I find more interesting than the license question is the
| software side. They mention a pre-loaded SD card with SDR
| applications, which probably means GNU Radio or something built
| on top of it. If they release the beamforming DSP pipeline as
| open source, that is genuinely valuable -- most phased array
| signal processing code is locked behind defense contractor
| NDAs. Having a reference implementation that people can study
| and modify on commodity hardware at the 399 dollar price point
| would be a significant contribution to the SDR community
| regardless of when the repo goes live.
| mrtnmcc wrote:
| the licensing of the software/firmware/hardware is shown at
| https://moonrf.com/updates/#faq
| O5vYtytb wrote:
| > Power Supply: 12 V DC ([?]1.5 kW peak)
|
| That's a lot of juice for 12VDC
| lutusp wrote:
| >> 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.
| numpad0 wrote:
| 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
| lutusp wrote:
| 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.
| jacquesm wrote:
| I 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.
| mrtnmcc wrote:
| the open-source licenses are listed at
| https://moonrf.com/updates/#faq
| CamelCaseCondo wrote:
| 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.
|
| [1] https://news.ycombinator.com/item?id=45949352
| mrtnmcc wrote:
| It's open source. Here is the GitHub: https://github.com/open-
| space-sdr/main
| jacquesm wrote:
| That wasn't there when I wrote that comment.
| go_artemis wrote:
| found it at the very bottom of the updates page
| royskee wrote:
| 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...
| lofaszvanitt wrote:
| :DDD
| mrtnmcc wrote:
| 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
| ck2 wrote:
| can amateurs bounce photons off the mirrors left there by Apollo
| 17 yet
|
| or does it still need industrial grade lasers?
| wolvoleo wrote:
| 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.
| infinitewars wrote:
| 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/
| wolvoleo wrote:
| 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.
| dtj1123 wrote:
| 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?
| kmbfjr wrote:
| 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.
___________________________________________________________________
(page generated 2026-04-06 23:01 UTC)