I got to see this in person at pacificon a few weeks ago. Also the creator is my friend from UIUC who I consider a brilliant rf/DSP engineer.
The demo was able to show and end to end tx chain from gnuradio to a receiver.
Really excited to see this! As there are a myriad of other things that this hardware can be used for as well.
We’re starting with the “Quad” tile — a 4 Tx × 4 Rx SDR designed for arraying — and expect to ship the first units toward the end of this year. They're actually quite capable as a standalone SDR. A Quad can interface directly with a Raspberry Pi 5, and we’ve built a combined enclosure for the SDR + Pi setup. You can run SDR software locally on the Pi or stream IQ samples over gigabit Ethernet to a remote PC.
Software support includes GNU Radio, Pothos SDR, and just about any tool compatible with SoapySDR. We’re also doing some fun demos, like visualizing Wi-Fi signal sources in real time ("Wi-Fi camera") and performing mm-scale 3D localization—a prerequisite for the automatic array calibration.
Larger arrays are assembled by simply tiling these Quads into an aluminum/PCB lattice framework, enabling anything from compact 4-antenna MIMO nodes up to 240-element lunar-bounce arrays. The goal is to have full phased-array capability by March 2026.
The broader vision behind open.space
is to make advanced RF and space-communications hardware open and accessible—so anyone can experiment with technologies once limited to national labs: moon-bounce (EME) links, satellite reception, terrestrial RF imaging.
Happy to answer questions here.
One thing I'm excited about getting working is mobile moon bounce!
Great question, the latest version has Tx RHCP, and then Rx either LHCP or RHCP controlled with RF switches (in each antenna). This allows point to point links (where the Tx pol and Rx pol should be the same), or "bounce links" where the circular polarization flips with the bounce. I should note RHCP Rx has a bit worse noise figure (LNA is different) but good enough for any line of sight.
It's not even a byte per second. The latency of the distances involved mean you're looking at around two seconds per round trip, plus a little extra because of the fuzziness of radio in space and absolutely everything that can distort it.
There's a lot of math that goes into selecting the right bit-width for the signal, which I ain't doing here and now [0], but most 24dB things tend to be 32bit for reasons. The arrays here are a bit more, but probably fit that kind of channel.
Assuming 32bit and 30dBi, you'd be sending at roughly 20-30MHz, and receiving at about 1kHz. (Less if you hit bad weather.)
If the goal is only to communicate with people on the other side of the world, HF ionosphere skip can do that with cheap 100-year-old technology (although transistors make it easier).
I assume the goal is to do something cooler than that.
The entire HF band, including the parts already used for something, is only 27 MHz of bandwidth, it's full of noise, and at any given time only a fraction of it can propagate to the other side of the world, dependent on time of day and, literally, sunspots. This antenna has 1100 MHz of bandwidth, the analog front end has 40 MHz for any given conversation, and noise levels are much lower. It could conceivably deliver Shannon bit rates one or more orders of magnitude higher. But it only works when the moon is visible to both sides of the connection.
I discussed these possibilities and some more challenging ones in 02013 in https://dercuano.github.io/notes/ultraslow-radio.html, although I was considering laser moonbounce rather than phased-array microwave moonbounce because of the higher antenna gain available.
Not impossible, just extremely difficult. I'm a ham and getting some contacts over moonbounce is a personal goal of mine. Historically this kind of thing has required some pretty large antenna arrays and very high power though:
Isn't there a moon bounce mode in WSJT (or one of those digital modes) that provides enough coding gain that 100W and a single large Yagi is enough? I seem to recall hearing something like that... but, yeah, on CW a monster antenna and the legal limit of 1500W seems to be the median system.
A long time ago I started collecting parts for a 432MHz EME system. Life got in the way and I never built it out. Good luck with your endeavor!
Yeah... so free space path loss at legal frequencies for hams this thing can transmit on is ~283dB. Neat idea but consider me skeptical. Having said that I can see some interesting applications for this kind of gear, EME seems overly optimistic though.
At those power levels they would have to use some kind of highly error-corrected modulation and coding scheme to provide enough coding gain to overcome the path loss. I agree they are pretty optimistic, but until they detail their modulation scheme, it's hard to tell.
A few years ago I was experimenting with 900 MHz LoRa for a work project -- we had need to communicate a very small data payload from inside elevator cabs, with forgiving latency requirements. So we took a LoRa board to a hotel building 2 city blocks away from our lab and cranked the coding gain up to the max, which gave us about a 1 byte payload every second. Perfectly sufficient for our application. Astoundingly, we had great copy in our lab even when the doors of the elevator cab were closed, inside a building 2 blocks away. I can't remember the power level, 500mW I think, but I may be wrong.
It's 1 watt per antenna. They have 240, or 53.8 dbm. So assuming 39.3 and your 283 (which seems to be around what I'm seeing online) that's -283+(39.3*2)+53.8=-150.6 dbm receive power. That should be plenty.
Yeah that is what is used for moonbounce today (if not full legal power - 1500W for US amateurs) but these little panels won't put out anything remotely close to that. Hence my skepticism.
KA1GT recently found a $100 “solar cooker” dish on AliExpress. Also available on Amazon. It was tested back in August.
Announced on the EME Facebook Group: https://www.facebook.com/share/p/19zLsGZiE7/?mibextid=wwXIfr
Output power was 500w
There's nothing that can't be modulated. Lol.
I got to see this in person at pacificon a few weeks ago. Also the creator is my friend from UIUC who I consider a brilliant rf/DSP engineer.
The demo was able to show and end to end tx chain from gnuradio to a receiver. Really excited to see this! As there are a myriad of other things that this hardware can be used for as well.
Great seeing you at Pacificon!
We’re starting with the “Quad” tile — a 4 Tx × 4 Rx SDR designed for arraying — and expect to ship the first units toward the end of this year. They're actually quite capable as a standalone SDR. A Quad can interface directly with a Raspberry Pi 5, and we’ve built a combined enclosure for the SDR + Pi setup. You can run SDR software locally on the Pi or stream IQ samples over gigabit Ethernet to a remote PC.
Software support includes GNU Radio, Pothos SDR, and just about any tool compatible with SoapySDR. We’re also doing some fun demos, like visualizing Wi-Fi signal sources in real time ("Wi-Fi camera") and performing mm-scale 3D localization—a prerequisite for the automatic array calibration.
Larger arrays are assembled by simply tiling these Quads into an aluminum/PCB lattice framework, enabling anything from compact 4-antenna MIMO nodes up to 240-element lunar-bounce arrays. The goal is to have full phased-array capability by March 2026.
The broader vision behind open.space is to make advanced RF and space-communications hardware open and accessible—so anyone can experiment with technologies once limited to national labs: moon-bounce (EME) links, satellite reception, terrestrial RF imaging.
Happy to answer questions here.
One thing I'm excited about getting working is mobile moon bounce!
Will you have arrays with the opposite antenna polarity for point to point links? That is, LHCP (Tx), RHCP (Rx) instead of RHCP (Tx), LHCP (Rx).
Great question, the latest version has Tx RHCP, and then Rx either LHCP or RHCP controlled with RF switches (in each antenna). This allows point to point links (where the Tx pol and Rx pol should be the same), or "bounce links" where the circular polarization flips with the bounce. I should note RHCP Rx has a bit worse noise figure (LNA is different) but good enough for any line of sight.
The moon is so useful.
For someone not well versed with the terminology, can someone please tell what kind of bitrate this can provide? In bytes per second.
It's not even a byte per second. The latency of the distances involved mean you're looking at around two seconds per round trip, plus a little extra because of the fuzziness of radio in space and absolutely everything that can distort it.
There's a lot of math that goes into selecting the right bit-width for the signal, which I ain't doing here and now [0], but most 24dB things tend to be 32bit for reasons. The arrays here are a bit more, but probably fit that kind of channel.
Assuming 32bit and 30dBi, you'd be sending at roughly 20-30MHz, and receiving at about 1kHz. (Less if you hit bad weather.)
So... 1 bit per second. Not byte. Bit.
[0] https://www.spaceacademy.net.au/spacelink/spcomcalc.htm
This is obviously incorrect. Latency is not the same as bandwidth. EME hobbyists will bounce voice signals off the moon.
Ok so ... moon is slow going.
Thank you so much. Are these rough calculations based on the smallest (quad), mini or the large array?
That was for the large array, assuming you were bouncing from you to moon and back again.
Point-to-point on the Earth would actually be semi-decent, as another comment pointed out.
No, if you do the math it's about 40 bytes per second (300bps) for Earth-Moon-Earth using their 240-antenna array.
Care to share the math, if you've done it?
It's 1.3 to 1.6 seconds each way to the moon, by radio link.
JPL's much, much, much bigger arrays can only achieve 64kbps.
That would be with laser, which isn't really relevant here?
I dont get it, How does latency affect bandwidth here?
Because we're not stationary, and nor is the moon. Latency means greater dispersion, and lower successful return rates.
A lightly coded (13/15 LDPC) 256QAM OFDM signal at 40 MHz wide could do 250 Mbps.
Or 31.25 million bytes per second if you prefer.
This would be for a point to point terrestrial link. OFDM probably wouldn't work for EME (at any power level).
If the goal is only to communicate with people on the other side of the world, HF ionosphere skip can do that with cheap 100-year-old technology (although transistors make it easier).
I assume the goal is to do something cooler than that.
The entire HF band, including the parts already used for something, is only 27 MHz of bandwidth, it's full of noise, and at any given time only a fraction of it can propagate to the other side of the world, dependent on time of day and, literally, sunspots. This antenna has 1100 MHz of bandwidth, the analog front end has 40 MHz for any given conversation, and noise levels are much lower. It could conceivably deliver Shannon bit rates one or more orders of magnitude higher. But it only works when the moon is visible to both sides of the connection.
I discussed these possibilities and some more challenging ones in 02013 in https://dercuano.github.io/notes/ultraslow-radio.html, although I was considering laser moonbounce rather than phased-array microwave moonbounce because of the higher antenna gain available.
> I assume the goal is to do something cooler than that.
Yes. Bounce the signal off the moon. The moon.
What if we tried more power?
I started reading thinking it was impossible but it has been done with other devices https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Ear...
Not impossible, just extremely difficult. I'm a ham and getting some contacts over moonbounce is a personal goal of mine. Historically this kind of thing has required some pretty large antenna arrays and very high power though:
https://hamradio.engineering/eme-moonbounce-bouncing-signals...
http://www.g4ztr.co.uk/app/download/13284489/RaCcom_Feb14+EM...
http://www.g4ztr.co.uk/app/download/13300096/Radcom_Mar144+E...
Isn't there a moon bounce mode in WSJT (or one of those digital modes) that provides enough coding gain that 100W and a single large Yagi is enough? I seem to recall hearing something like that... but, yeah, on CW a monster antenna and the legal limit of 1500W seems to be the median system.
A long time ago I started collecting parts for a 432MHz EME system. Life got in the way and I never built it out. Good luck with your endeavor!
I'm skeptical, but how can you not cheer for this? Sounds so awesome.
Have you read Three Body Problem?
Expected array gain: ~39.3 dBi / EIRP: ~63.1 dBW
Tx power: 1 W per antenna
Yeah... so free space path loss at legal frequencies for hams this thing can transmit on is ~283dB. Neat idea but consider me skeptical. Having said that I can see some interesting applications for this kind of gear, EME seems overly optimistic though.
At those power levels they would have to use some kind of highly error-corrected modulation and coding scheme to provide enough coding gain to overcome the path loss. I agree they are pretty optimistic, but until they detail their modulation scheme, it's hard to tell.
A few years ago I was experimenting with 900 MHz LoRa for a work project -- we had need to communicate a very small data payload from inside elevator cabs, with forgiving latency requirements. So we took a LoRa board to a hotel building 2 city blocks away from our lab and cranked the coding gain up to the max, which gave us about a 1 byte payload every second. Perfectly sufficient for our application. Astoundingly, we had great copy in our lab even when the doors of the elevator cab were closed, inside a building 2 blocks away. I can't remember the power level, 500mW I think, but I may be wrong.
People use WSJTX software and Q65 mode
It's 1 watt per antenna. They have 240, or 53.8 dbm. So assuming 39.3 and your 283 (which seems to be around what I'm seeing online) that's -283+(39.3*2)+53.8=-150.6 dbm receive power. That should be plenty.
It's theoretically possible.
63.1 dbW = 93.1 dBm (240 watts + 39.3 dB gain)
path loss at 5760 MHz = 283.2 dB (at perigee)
RX gain = 39.3 dB
93.1 - 283.2 + 39.3 = -150.8 dBm
Noise floor at 1.2 dB noise figure and 500 Hz bandwidth = -151.9 dBm
SNR = +1.1 dB (easily detectable by ear with CW).
A few hundred Watt at a minimum would be my first guess.
Yeah that is what is used for moonbounce today (if not full legal power - 1500W for US amateurs) but these little panels won't put out anything remotely close to that. Hence my skepticism.
This was a Cold War thing to surveil Soviet air defense radars.
Latency?
1 sec up and 1 sec down... more or less. Speed of light and distance to the moon, two times.... roughly.
I'm more interested in bitrate.
300bps