[HN Gopher] Bouncing a LoRa message off the moon
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Bouncing a LoRa message off the moon
Author : fortran77
Score : 93 points
Date : 2021-12-06 17:36 UTC (5 hours ago)
(HTM) web link (electronics360.globalspec.com)
(TXT) w3m dump (electronics360.globalspec.com)
| metal_am wrote:
| I'm having a hard time seeing what's special about this. This has
| been a HAM radio thing for a long time.
|
| https://en.m.wikipedia.org/wiki/Earth-Moon-Earth_communicati...
| sneak wrote:
| They did it with a data modulation mode (LoRa) which has the
| following properties:
|
| - it is very resistant to noise
|
| - it is low power
|
| - it is popular
|
| - it is patented/proprietary
| ricardobeat wrote:
| It's basically Wi-Fi to the moon. At very low bandwidth, but
| still amazing.
| bartkappenburg wrote:
| Cool! Dwingeloo is like 40km (25 miles) from here. They're doing
| interesting stuff over there (eg. being a test site for LOFAR
| [0]).
|
| [0] https://en.wikipedia.org/wiki/Dwingeloo_Radio_Observatory
| marcodiego wrote:
| LoRa 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.
| gregwebs wrote:
| The YoLink products use LoRa for home automation. I am quite
| happy using their water leak sensors now. You don't need the
| quarter mile range, but they communicate with low power
| successfully in situations where higher frequencies might have
| reflection issues.
| nogridbag wrote:
| I'm also a big fan of YoLink water sensors. I installed them
| under every sink and have probes going into the sump pumps to
| detect high water levels. We have a single hub in the basement
| and it has no issues reaching sensors two floors up at the far
| corners of the home.
| anfractuosity wrote:
| When it says amplified to 350W, how's that work out of interest,
| is that done actively with a 'power amplifier' or..?
| focusedone wrote:
| This. I guess the big deal is supposed to be the single chip
| transceiver, but that's not a huge step past some small SDR
| units hams use. Throw 350 watts behind it and most any potato
| could EME.
| authed wrote:
| Decoding LoRa: https://revspace.nl/DecodingLora
| YXNjaGVyZWdlbgo wrote:
| -
| ineedasername wrote:
| I'm not sure that was the point. Either way, accounting for the
| doppler effect is possible. We generally know what the offset
| will be for a given frequency based on the moon's position in
| the sky. The article itself mentions that the signal behaved
| predictably with respect to the expected doppler shift.
| jmole wrote:
| of 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.
| axegon_ wrote:
| I think this is a pretty good thing, certainly promising: IoT
| protocols are by definition accessible to the general public
| which gives a lot of potential for future developments. Surely
| not with LoRa in particular, given the microscopical size of
| the payloads but the fact that it is possible is really
| promising. Just a decade ago, this would have been unthinkable
| for any hobbyist. Hell, even the prices of sdr's a decade ago
| were off the charts and today a semi-decent one to get you
| started costs a few bucks.
| gh02t wrote:
| LoRa isn't really a consumer protocol, more of an industrial
| one. It's mostly intended for widely distributed sensor
| networks.
| Rebelgecko wrote:
| I think Amazon Sidewalk (included w/ every Alexa now) is
| built on top of LoRa
| blacksmith_tb wrote:
| It looks like they added LoRa to the most recent Ring
| Bridge[1], but most older Sidewalk devices do their
| connecting over wifi. Seems likely other new ones will do
| both.
|
| 1: https://fccid.io/2AEUPBHARB001/RF-Exposure-Info/RF-
| Exposure-...
| intpx wrote:
| 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
| intpx wrote:
| Maybe i'm thinking zigbee?
| gh02t wrote:
| Zigbee has always (or at least, for a long time) targeted
| a mixture of consumer and industrial applications and is
| focused on relatively short range mesh networks. It does
| have a lot of consumer uses now, it's one of the big
| protocols used for home automation. Not sure of the exact
| history of LoRa, but widely distributed oil well sensors
| would definitely fit the intended use of LoRa.
| Agriculture is another good use case.
|
| Low power sensors infrequently reporting (mostly one-way)
| small amounts of data back to a base station over really
| long distances is what it was originally designed for,
| though people have done other stuff with it. Zigbee is
| all about the meshing AFAIU.
| thedougd wrote:
| Zigbee has a serial bus mode that's identical to RS-485
| in practice. There were/are so many industrial
| applications of RS-485 that they could instantly convert
| to wireless mesh with a zigbee daughter board or chipset.
| 'Pro' versions had ~1.5 mile range between nodes.
| ineedasername wrote:
| Alien 3: We need to find this Alexa person
| walrus01 wrote:
| lora is used for more than just consumer iot control - it's one
| of the most effective ways to bridge a serial connection across
| a very low bandwidth/RF difficult or weak link.
| noman-land wrote:
| I think it would be extremely neat to have a fully citizen run
| global p2p infrastructure that is nearly free, resilient to
| electrical and internet outages, and able to reach remote and
| distant places.
| URSpider94 wrote:
| Check out https://helium.com - it's a blockchain-based LoRA
| network, where the blockchain is used to reward uptime and
| certainty of location of the base stations. Transmissions can
| be received from 10 miles or more away, if the receiver is
| located high enough.
| __MatrixMan__ wrote:
| I'd crowdfund the maintenance of LoRa repeaters on nearby
| mountaintops. I'd also do the hiking to maintain them, sounds
| like as good a premise for adventure as any.
| genewitch wrote:
| Winlink basically does this. I'm unsure if there's software
| for other OS, but winlink is email-ish that is p2p on the
| backend, and can also be used point to point. And don't tell
| anyone I said this, but if you have a real hardware modem for
| winlink you can get 3KB/second. It works on any frequency you
| can tune to.
|
| Also APRS, even though it seems like Google has a huge
| interest in it, is also a p2p communication network, running
| on 144mhz and 10mhz.
| giantg2 wrote:
| A consumer protocol, but also way over consumer power level
| (350W). No wonder it's the furthest LoRa message sent. Let's
| bump it up to 1kW and break the record again...
| numlock86 wrote:
| 1kW? Are you crazy??? Let's see 25mW, which is the maximum
| you are allowed to use in Germany for 868 MHz ...
| imoverclocked wrote:
| I agree, if we are doing this, go big. 1MW would be far
| more exciting and the experiment definitely wouldn't go
| unnoticed.
| stavros wrote:
| To be fair, it can do a few km at 25 mW, which is fairly
| good for consumer range.
| fortran77 wrote:
| That was the Effective Radiated Power. The actual transmitter
| was outputting consumer output levels.
| giantg2 wrote:
| I thought most FCC rules are based on effective power and
| that this wouldn't be legal for terrestrial/consumer use?
| jjoonathan wrote:
| Because it doubles the range of the PR stunt.
|
| If they had driven the chip with a raspberry pi (or, more
| importantly, said so enough times to land the keyword in the
| article), they could have quadrupled the range of the PR stunt.
| Breefield wrote:
| 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.
| detaro wrote:
| Moonbounce isn't practical for any real application nowadays.
| It's a fun experiment and a PR stunt.
| Breefield wrote:
| Why isn't it practical? Background noise makes it
| unreliable?
| vvoid wrote:
| 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 wrote:
| 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.
| [deleted]
| detaro wrote:
| 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.
| op00to wrote:
| Path loss.
| teraflop wrote:
| 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 wrote:
| it would be interesting to see where else it could've been
| picked up. like a scatter dispersion map
| snovv_crash wrote:
| 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.
| walrus01 wrote:
| > 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.
| mcpherrinm wrote:
| Amateur radio operators routinely do earth-moon-earth radio
| communication using specifically designed protocols. So using
| LoRa here is surely the point: to show what it can do -- not
| that it can be done at all.
| dhuk_2018 wrote:
| Hams around the world are already bouncing signals off the moon
| with a lot less power and gain, using modern signal processing
| techniques.
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(page generated 2021-12-06 23:00 UTC)