[Breefield]

Just a guess: given that LoRa operates on line of sight, when trying to update a gateways with sensor status (e.g. GPS position of tracked item) the operator won't be able to get realtime reports if the gateway isn't positioned at a high enough altitude relative to the sensor.

You can mitigate this by having many gateway/collectors at high points on buildings/hills, but bouncing signals off the moon seems like an interesting alternative for connectivity in low coverage locations...

Perhaps this is clear to you I'm just trying to think it through out loud.

[teraflop]

This is a cool stunt, but it's not at all practical for IoT communications. For one thing, it requires a big dish and a huge amount of transmission power to get a barely-distinguishable reflected signal.

The other big issue is that it doesn't scale, because there's no directionality: the reflected signal will be scattered off the moon and received everywhere on the hemisphere of earth where the moon is above the horizon. So every single device that tried to use this strategy would have to contend for the same chunk of bandwidth.

[oolonthegreat]

it would be interesting to see where else it could've been picked up. like a scatter dispersion map

[detaro]

Moonbounce isn't practical for any real application nowadays. It's a fun experiment and a PR stunt.

[Breefield]

Why isn't it practical? Background noise makes it unreliable?

[detaro]

The fact they used a 35m radio telescope as the receiver station here, and transmission powers way over legal limits for normal LoRa-like applications is a pretty good hint. You lose a crazy amount of signal with moonbounce, the effort is always easier to put into different methods instead. AFAIK it's only non-experimental use predates human-made satellites (US military, as a further channel to reach far-away war ships even if terrestrial propagation conditions are bad). If you can't use satellites, and can't have a receiver station within a few thousand miles of your transmitter, then it maybe is sort-of an option, but that's not really a situation you have anymore.

Amateur radio operators still do it, and with purpose-made codecs and really slow speeds it's not that out of reach (i.e. at least for those you don't need a radio telescope dish), but that's just because it's an interesting challenge.

[vvoid]

Background noise - that's one way to put it! The path loss is around 250 dB, so a practical amateur moonbounce station makes use of a very powerful RF amplifier feeding an array of yagi antennas, all mounted on an altitude/azimuth rotator - in other words, it's a radio telescope, and the receiving side hopefully has something similar. You can do a google image search for "moonbounce," the setups are kind of amazing. A lot of investment mostly to exchange morse and specialized low-bandwidth digital modes.

The upshot is that you can communicate with any station that can also see the moon - somebody on the other side of the planet, 12,000km away. Plus there is the unique experience of hearing your own transmission echo, two seconds after you cease.

This kind of setup is well within reach for a commercial enterprise but will never be practical for IoT owing to the laws of physics. On the other hand, there is SNOTEL, a system that bounces snowpack telemetry off of the ionized trails left by meteors...

[virtue3]

Because the moon is 238,900 mi away. Nor does it stay locked in position. Nor is it perfectly reflective (albeit quite a high albedo) nor a perfect sphere.

[bigiain]

This comment has made me need to go listen to Albedo 0.39 again:

https://www.youtube.com/watch?v=ygcBT87K6BY

[op00to]

Path loss.

[snovv_crash]

LoRa doesn't have to be LOS, it depends on the carrier frequency you use. 900MHz LoRa is used for building penetration of control signals for racing drones, for example, with the open source ExpressLRS system.

[bigiain]

I have a bunch of (low powered, runs for 24+_hrs on a single 18650 cell) 433MHz Lora/Meshtastic nodes - I can get 10km or so range with simple 1/4 wave dipoles indoors in urban environments. Hills kill it a bot, but I've got one shot that gets 3.3km non line of sight with a hill between the nodes.

[walrus01]

> given that LoRa operates on line of sight

not exactly, no, one of the most common uses for LoRA is in the US 915 MHz band where it can function in a very much non line of sight environment.