Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Open-source communications by bouncing signals off the Moon

open.space

Post reply on HN
Print view View original

11–20 of 88 posts

Re: Open-source communications by bouncing signals off the Moon

#11

Post by drmpeg »

cactacea wrote: post #3

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.

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).

Re: Open-source communications by bouncing signals off the Moon

#12

Post by Neywiny »

cactacea wrote: post #3

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.

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.

Re: Open-source communications by bouncing signals off the Moon

#14

Post by firesteelrain »

dbcurtis wrote: post #10
cactacea wrote: post #3

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 c…

People use WSJTX software and Q65 mode

Re: Open-source communications by bouncing signals off the Moon

#16

Post by kieranl »

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.

Re: Open-source communications by bouncing signals off the Moon

#17

Post by mrtnmcc »

kieranl wrote: post #16

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!

Re: Open-source communications by bouncing signals off the Moon

#18

Post by [deleted] »

cactacea wrote: post #8
jacquesm wrote: post #6

Earlier quoted context omitted.

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.

[deleted]

Re: Open-source communications by bouncing signals off the Moon

#20

Post by lll-o-lll »

dreamcompiler wrote: post #19

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.

> I assume the goal is to do something cooler than that.

Yes. Bounce the signal off the moon. The moon.

Post reply on HN