I’ve got a couple of use-cases that I haven’t seen anyone mention but I think are pretty cool and figured I’d mention what I’m working on.
I’m adding a Meshtastic LoRA transponder to the top of the mast on my sailboat along with a decent antenna to serve a couple of purposes.
The first purpose is for each of the crew to keep a LoRa device on them (shoulder area) so that if they fall overboard I can raise an alarm either because the signal dissapears or is beyond a “safe distance” and hopefully the device should stay above the water and help the remaining crew find them even in dark conditions out at sea.
Second purpose is as a way of communicating and tracking/finding crew that’s shoreside where there aren’t any cell phone towers or other means of communication though it certainly also helps in more populated marinas and cities.
In the process I’ve been trying to solve a couple of problems that people might be able to help me with.
Sailing means crossing regulatory regions but from the datasheet it looks like the SX1262 LoRa radio can cover 433/868/915MhZ but people still make 3 different kinds of devices. Does anyone know if it’s possible to switch frequencies in software assuming the antennas are multi-band or do the devices have band-filters limiting them to a specific frequency?
If no devices support multiple bands is the best way to use a RAK WisBlock based device and switch out the radio?
The reason I’m trying to avoid having multiple devices is that changing the radio means a trip up the mast and keeping 2 devices per person around and making sure they don’t get mixed up)
Does anyone know of a water tight (IP67+) case for a supported Meshtastic device?
The best I’ve come up with is LILYGO® TTGO T-Echo and waterproofing it or designing a new case.
I can see plenty more marine use cases like cheap low power AIS alternatives, messaging with other vessels if they happen to be on a collision course, booking visitor berths, reporting in for customs/immigration but I think those all require a more widespread adoption.
We’re building a “showcase” section of our website. This project would be a great addition. Please keep eye out for the showcase. We’d love to have you.
1 - There may be some matching circuitry (mostly a just capacitor or inductor) with the intended frequency, but in general all that does is adjust the SWR of the circuit to be “slightly better”. There’s no low-pass/high-pass or notch filter on the PCB. It’s really splitting hairs (think, a few percent difference). The biggest difference is in the antenna used. 868/915 are fairly similar and can generally use interchangeable antennas (but tuned antennas are better). You may be able to find multi band antennas to cover 433/868/915MhZ. Check digikey.
2 - I use this: https://amzn.to/3Emte4l … it’s easy to pass bulkheads for the antenna and charging.
Thanks for the recommendations, the Pelican case seems like a good match for a waterproof case for use onboard though I wish there was something as small as the ILYGO® TTGO T-Echo.
For the masthead repeater unit I’m planning on using a Poynting OMNI-402, it only has 1-3dBi in the relevant frequencies but I’m afraid anything with more gain won’t give a good signal when the boat is bobbing around.
Base on your description I want to talk about my plans on building a new dedicated board for Meshtastics.
Right now the firmware is running on either a nrf52840 or ESP32 MCU, and Lora is an SPI device and this chip is highly optimized and there’s no multiband version exist as I know. I want to make a new board with an Lattice FPGA carrier board to multiplex the IOs of each nrf52 or ESP to a new standardized sensor daughter board, with power dissipation monitoring and on demand I2C or SPI routing on a carrier board. What this means in plain English is that, you can choose the board you want, either MCU, any number of SX16/17xx or any sensor, to coexist on a single device.
This was due to my initial frustrations of RAK4630 encounter, which IO is highly flexible of nrf52840 is capable of choosing whichever you want on any pin, but constrained by Arduino firmware and the expansion routing of RAK WisBlock carrier board.
And if you want to use Lora beacon as a Direction Finding Tag, you will need a Watson-Watt or DF dedicated Antenna Array, and wideband SDR, and some GNURadio. I have done quite some work on that recently for non-Lora signals, but Lora signals might also could be as effective.
Right now I am finishing my first RAK4631 based board. If you are interested in testing a 3D SLS printed IP67 shell for it, I can design the hard point specific to your mounting requirement.
If you want to use Lora->Protobuf->Arduino->IO to control some relays, I would like to design some board for your project if you have very specific and thought out requirements.
For nodes located outdoors, I’ve used pvc pipe with end caps and they’ve worked very well for me. Not in a marine environment but if you glued a plain cap on one end and a screw lid on the other it should work pretty well. Easy to mount them anywhere, and enough room inside for the antenna (my next nodes will be TBeams with ipex connectors and a pcb strip antenna). Add a waterproof gland for power input and you should be good as.
I’d suggest just trying the little antenna that comes with the device and mounting the whole thing up the mast. They are omnidirectional and these lora modems are awesome line of sight
Are you thinking that you want to run multiple bands at the same time?
I started thinking along similar lines but since I don’t strictly need to run multiple bands at the same time I thought that there must be a way to get a single SoC to just change the frequency using software and figured I’d ask on this forum. I think an alternative approach would be to split up the SoC and use an external SX16/17xx?
Thanks for the offer, for now I think I can work with an off the shelf RAK block system for development, my boat is on dry land until spring so I’m not in a big hurry. I already have a pretty big relay board that I designed last winter so I think I’m OK on that front
Thanks, it’s a bit chunky but it’s essentially a breaker panel and relay board all in one, I’d probably make some changes if I’d redesign it and I’d love to add individual circuit power monitoring but I was already pushing the limits for size and cost because of the thick copper required to handle that amount of current.
What you don’t see on the picture is that it’s also got an interface for Seatalk and NEMA2000 giving me access to all other sensors and devices onboard. I’ll need to figure out a nice way to make it work with Meshtastic but it shouldn’t be too hard since I have a Raspberry Pi with Node Red onboard. Probably just serial but we’ll see.
You are not likely to run different bands on a specific chip, they might have different RF front end on die or specifically tuned on that band frequency.
Some of Lora chips runs on wide band, you will need RF switch and filters/LNAs for different band, as the RF sensitivity might or performance might suffer.
Reading the spec sheet for the SX1262 it didn’t look like there were multiple versions hence my confusion and wondering if there were band pass filters or/and one-time programmable memory to hard set the main frequency or if it could be changed after the fact?
I honestly don’t know much about RF engineering (I just dabble) but I did wonder if a single filter could do the job since 433 x2 isn’t too far of from 866-870 and 915-928, something like a 448.5Mhz ± 15.5Mhz filter second harmonic would be 866-928, I guess the alternative would be to use a programmable filter?
I haven’t yet dig much (honestly, null) experience make a Lora board not calculate the RF requirement it required. I will look into it when I start make my own Lora board.
Some guide lines in RF i believe:
*You need to filter LNA path first, in RF. Then do filter again after Mixer. Harmonics usually not a good thing and intuitively it won’t be considered to use as a multi-band signal processing technique;
*and designing a wide band filter to make both work sounds not practical, in IF.
*Lora signal is kinda chirp signal it might requires special attention and i don’t yet have experience.
Usually ASIC designer will leave some room for system designers to play with, if I found something interesting I will report back.
Following up on the direction finding discussion I think the following might be a good match though I wonder if it would have to also have the frequency shift information and timing that the LoRa devices have/use.
Hi ant
I have one of these for some time. Their Python script running on RPI is a bit wonky (a matrix math lib with some optimization algorithm). The bandwidth of this device is very limited, about 3.4MHz, you will need your own code to jump between different band, of course, and their stock Android program is a GIS and closed source.
All you need is the difference of phases on the antennae to make direction estimation, the chirp freq differences on them are the same i think.
Semtec already has the sx1280 2.4ghz LoRa SoC with range finding. It’s range isn’t as good as the sx1262, but it’s frequency is global and it’s ToF ranging function is supposed to be accurate to several meters.
If you haven’t heard of secure scuttlebutt, it’s a cool project started by a sailor that uses gossip based offgrid communication. Right now it only supports Bluetooth and WiFi, but I hope to someday implement it on LoRa.
Interesting, although not as good as having a direction and point locator just having the range would be beneficial, I wonder if there are any plans to add this functionality to the other frequencies later.
Hi! I’m also interested in how LoRa / meshtastic might be used with sailboats. I’d also considered data/text chat between crews on different boats in line of sight range. There’s other systems for this and VHF for voice, but I thought it’d be neat since the nodes (where each sailboat is a node mounted to the mast) can already announce its GPS position. Again, there’s other systems for location, so this would be less serious for actual navigation. (Although the sailboats I’m most interested in are too small for radar and sometimes camp out or “go on raids” to remote beaches rather than stick to marinas, so something less serious would be entirely appropriate.)
I’d messed around with secure scuttlebutt in the past, and I’m not entirely sure it is appropriate for LoRa. Happy to be proven wrong, though.
Some similar, cross-app + multi-networking-stack text based chat would be a huge win, though. Meshtastic and Disaster.radio have both implemented text but they’re not compatible. matrix.org and xmpp are probably both too heavy and web-centric to work.
