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

:DDD

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

It's open source. Here is the GitHub: https://github.com/open-space-sdr/main

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

>> 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.

The 1 GB RPi-5 is only $45 still, hopefully it stays that way :)

the open-source licenses are listed at https://moonrf.com/updates/#faq

looks like there have been updates since then: https://moonrf.com/updates/

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.

> 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.

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.

> 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.

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.

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.

Any that forbid or restrict satellite comms?

Don’t use this in Iran.

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...

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/

All I guess? If you're licensed you should know what you can and can't do.

the licensing of the software/firmware/hardware is shown at https://moonrf.com/updates/#faq

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.

> 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.

> 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/

EIRP. There's some gain involved.

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...

> 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.

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."

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.

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.

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.

correct, one Pi-5 for the MoonRF. The beamforming computation is done digitally "on the fly" in round-robin across the sixty QuadRF boards.

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.

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.

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.

> 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.

At a functional range resolution of 4M would it even qualify as violating ITAR even if it was tweaked to do so?

The MoonRF array is a full 1 meter diameter as shown on the page

I'm asleep and I misread that as 10cm. Thanks.