Impressed by the headline then I read they amplified it to 350W. Less impressive.
Bouncing a LoRa message off the moon
51–60 of 71 posts
Re: Bouncing a LoRa message off the moon
#52Earlier quoted context omitted.
LoRa isn't really a consumer protocol, more of an industrial one. It's mostly intended for widely distributed sensor networks.
Wasn't it designed for sending sensor data from oil wells spread out over vast swaths of land or something? I've always though of it as shortwave/vhf for packets
Started out being used for satellite communication between satellites. It's point to point nature and multiple frequency legs itself to sensor networks over extended distance or in dense areas like cities.
Re: Bouncing a LoRa message off the moon
#53of all the things to bounce off the moon, why a consumer IoT protocol? Alien 1: The humans are talking again. Alien 2: What did they say? Alien 1: The front door is locked.
The spread spectrum "chirps" that LoRa uses are really effective in allowing you to grab tiny signals from unreasonably large noise floors.
You can see the really obvious signal in the waterfall chart here: https://revspace.nl/DecodingLora
It's way way easier to grab those chirps out of the noise than FSK FM modulated signals or worse AM anything.
Re: Bouncing a LoRa message off the moon
#54Earlier quoted context omitted.
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 int…
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.
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.
Re: Bouncing a LoRa message off the moon
#55Earlier quoted context omitted.
Why isn't it practical? Background noise makes it unreliable?
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.
This comment has made me need to go listen to Albedo 0.39 again:
Re: Bouncing a LoRa message off the moon
#56LoRa has some ridiculous range with minimal use of power. Being able to bounce it off the moon may allow communication between a whole Earth hemisphere. At the least, this allows beyond-horizon communication.
A personal messaging system for you and all your friends who have a 35m radio telescope dish in their backyards...
Re: Bouncing a LoRa message off the moon
#57With a 25 meter dish, moonbounce is not hard. That's a sizable radio telescope. Radio hams have done this with a 3m dish and 150 watts.
Re: Bouncing a LoRa message off the moon
#58That would be a cool physics lab to replace the Lucite speed of light test
Re: Bouncing a LoRa message off the moon
#59LoRa has some ridiculous range with minimal use of power. Being able to bounce it off the moon may allow communication between a whole Earth hemisphere. At the least, this allows beyond-horizon communication.
They're bouncing them off the retroreflectors on the moon though, right? So that doesn't necessarily translate to being able to send messages to anywhere on the hemisphere.
Re: Bouncing a LoRa message off the moon
#60LoRa has some ridiculous range with minimal use of power. Being able to bounce it off the moon may allow communication between a whole Earth hemisphere. At the least, this allows beyond-horizon communication.
They're bouncing them off the retroreflectors on the moon though, right? So that doesn't necessarily translate to being able to send messages to anywhere on the hemisphere.
No, the radio waves bounce off the moon's surface. The retroreflectors are not necessary for that, otherwise stuff like Earth-Venus-Earth bounces[1] would not be possible.
[1]: https://amsat-dl.org/en/earth-venus-earth-experiment-of-amsa...