> LoRa can reach a range of up to 3 miles (4.8 km) in urban areas, and up to 10 miles (16 km) in rural areas
In mountainous area LoRa on 868MHz band reaches over 100km. Last month we had a stratospheric balloon with a Meshtastic node attached. It established direct (albeit intermittent) connection between Warsaw and Berlin.
It's a real shame phones don't have something like this built in. I mean, we literally have satellite communication in every iPhone – or, depending on how you count, every LTE phone, period!
Technically, it seems like 90% of what's required is already there anyway, but due to commercial and political pressures, we'll probably never see it happen.
There's a lot of cool radio-related things our smartphones could do but probably never will for regulatory/political/commercial reasons like you note.
My pet idea is to make some use of longwave! You know those time signals broadcast around 60 kHz? They cover thousands of kilometres from one transmitter. At 60 kHz the wavelength is 5 kilometres long and the RF tends to diffract around objects like mountains, buildings, etc. that get in the way. Longwave tends to penetrate underground, and through Faraday cages meant for short wavelengths.
Those time signals broadcast, in effect, 60 bits a second. The receiver is dead simple electronically and requires almost no energy to run. What if we broadcast a more modern error-corrected data stream? Every device could be supplied with a receive-only stream of a few kilobytes a second of whatever. I admit it's a solution somewhat in search of a problem. Weather updates? Emergency alerts?
Reminds me of what the messenger on the Cybiko was trying to be. Too bad LoRa wasn't a thing back then, it would have been more useful if it had a better range.
I remember seeing these on some tech show here in the UK - and being in love with the idea - seemed so cool and 'archivable' for a young person to own. A few years later they were dirt cheap on ebay - new/boxed, but by then the itch had gone, but I wish now I'd bought one.
If you want something like this with asymmetric encryption, a qwerty keyboard, mesh range extension, and a GUI, try a T-Deck running Meshtastic.
yes!!!
Or get a rak device that has a better antenna and range than the T deck
Oooh, which one has a keyboard?
It uses the slow method where you push the same key until you get the letter you want to show up? Does anybody remember T9? You push the keys for the letters you want and it figures out what you're typing from a dictionary.
Yeah I thought he was going to say it uses T9 too, but it uses an inexplicably archaic chip so there's no way you could fit a dictionary on it.
For anyone looking for an off-the-shelf solution for wireless texting, I've used the BTECH GMRS-PRO. You can send messages on the device, but it's much easier to connect it to your phone via BLE and text through the app.
However, it uses GMRS bands, not LoRA, so all the FCC restrictions apply.
While I highly doubt you'd ever get in trouble, data transmissions on GMRS are severely restricted by the FCC. You obviously need the license (though it's just a fee and covers your whole family).
In any case, I'm pretty sure this device is illegal to use for short text messages. It doesn't appear to comply with several of the restrictions on digital emissions in 47 CFR 95.1787(a), namely it appears to have a removable antenna. Removable antennas are fine for regular GMRS use, but not when the device can send digital emissions.
https://www.ecfr.gov/current/title-47/part-95/subpart-E#p-95...
Also I'd be shocked if it enforced the time limits for digital transmissions in software. This leads me to believe it's not actually type-certified for use which then calls into question anything else it does. Caveat emptor.
The antennas on mine don't appear to come off, at least not easily. I read somewhere that they came off on the early models but are now glued.
It does enforce time limits. If I send a message or something that uses digital communication (like gps coordinates), it won't let me send another one immediately after.
Wow I'm surprised - I based my message of the manual on their site which pretty clearly shows a detachable antenna and says nothing about time limits. I wonder if they received something from the FCC saying they can't market a GMRS radio that isn't type-accepted.
Why wouldn’t they comply with tx duration? You don’t want excessively long tx as you can’t rx at the same time. You’ll lose messages.
There is no amount of time that guarantees you won't interfere with another user on a shared channel without time division. Any protocol used has to account for it no matter what.
But discussion of that is irrelevant because the regulation is no more than one every 30 seconds and each one can't be longer than 1 second in duration. This necessarily limits the length of messages you can send or requires more efficient modulation and/or weaker error correction at the tradeoff of worse weak-signal performance.
Can you elaborate on the restrictions? Is it just that the Baofeng allows you to transmit on some frequencies that aren’t legal or at power levels that aren’t allowed or is it not allowed in the US at all?
To use GMRS you need a license to be compliant with fcc. It’s not expensive I think $60 for 10 years and it covers your family.
You can then use GMRS. GMRS is all the same FRS channels plus several more. GMRS can also transmit at up to 50mw on some of the non-FRS channels.
To be using GMRS in compliance you have to use an FCC Part 95E certified device. These Baofeng / Btech devices are usually not GMRS certified. So you need a HAM license to use them. . . But HAM licenses doesn’t cover GMRS frequencies. So there is no technically compliant way to use these devices and check all the boxes. Even if you have both HAM and GMRS you are using a non Part 95E certified device. You’re likely fine as long as you’re not harassing people or causing interference. Generally the FCC is pretty reasonable. They send a letter saying knock it off before they knock on your door. But if you continue to harass people or use high power that causes interference then you will get a hefty fine.
At the very least get your GMRS license. But I encourage you to get your HAM license. I have found that often HAM nerds are into a lot of other stuff I like and my local club has been a welcome place to make friends and build fun stuff.
Btech markets devices that are GMRS type accepted, it's actually one of their main businesses these days to take Chinese developed radios and modify them slightly and get them GMRS approved in the US.
You need a ham license to do most anything with a Baofeng legally.
Baofeng does make GRMS- and FRS-specific radios that comply with FCC regulations.
Not true, GMRS licenses are much easier to get
While true, it's important to remember that not all ham radios that can transmit on GMRS bands are legal to do so. GMRS and FRS don't have the same "anything goes" allowances that ham operators have. Radios for these bands must be purpose built for these bands. Of course no one is going to know your compliant GMRS/FRS transmissions are coming from part 97 radio. Although most quality ham radios don't allow transmission on anything but the ham bands. The increased FCC enforcement of these Chinese radios means that many now have extra filters to reduce spurious emissions outside the ham bands, meaning they shouldn't work as well on GMRS and FRS.
If you want to use GMRS, buy a GMRS radio.
While people did get really fast at typing on those num keypads, there was a lot of RSI injuries among people who did it often. a number key bad might be the best compromise despite that, but don't lose sight of just how bad they were and take effort to avoid the issues.
> ATtiny814
Why do people still use these ancient chips?
> ATtiny814
I personally like the new(ish) attinys because they're cheap, plentiful, stupid easy to program, and can be put into extremely low power modes.
Are there any free-to-tinker spectrum allocations not subject to the duty cycle limitations?
Neat! At 24mA the suggested battery will only last 10 hours. Shouldn't it be possible to use such a LoRa device - at least in listening mode without an active display - for much longer time periods?
LoRa is actually pretty thirsty on receive.
You’d need some scheme for synchronization if you want to reduce power consumption.
To elaborate on this a little bit, the conventional use isn't peer-to-peer but rather sleepy IoT nodes that periodically wake up to send to a listening base station. The IoT node transmits and then waits a specified amount of time listening for a response back from the base station.
The tradeoff is:
- The end nodes can spend the vast majority of the time in deep sleep without the radios turned on.
- The base station has access to a bigger power source (usually line voltage) and doesn't care about turning its receiver off.
- You can't, however, send data to the end nodes at arbitrary points in time. You have to wait for them to send to you and you have to reply back to them before they go back to sleep.
In a peer-to-peer system like the one in the article you don't get to make this tradeoff.
There's no reason you couldn't do this in a peer-to-peer system too, especially if you only have a few nodes. Imagine for 2 nodes:
1. Each node transmits a beacon once per second.
2. While they aren't connected, each node listens for sub subset of time (say 10%).
3. Eventually one node will hear the beacon from the other. They can use this to synchronize clocks (the better your clocks the better this works).
4. Thereafter they just wake up periodically at the same time and one transmits a beacon to the other to synchronize (alternating whose turn it is).
It's the same idea as sleepy edge devices used in IoT, but just both ways. Quite a lot more complicated of course, but you can totally do it.
Receipt for LoRa is low power, its transmission that kills the battery
For any radio system, receiving continuously also kills battery, just not as fast as transmitting does.
Low-power requires you to turn the receiver off for extended periods of time, but what you can do there is limited by how interactive the device needs to be, and how much the power the transmitter is willing to waste on retries/longer preambles.
For proper low-power (e.g., devices with ≥ 1 year battery life on small batteries), you're likely to need sleep periods of minutes to hours, or only waking up on physical interaction.
Sort of. Keeping the receiver on and listening 24/7 is going to still use significantly more current than not having the receiver on and putting the microcontroller into a deep sleep mode. The approach in my sibling comment explains how IoT LoRaWAN devices are able to use ~0 current the vast majority of the time and run off, say, a CR2032 battery.
Receiving is just transmitting nothing to see how it's getting disturbed
It's very beautiful, but are there apps that do this? Isn't that what Briar does? I think there may have been some others.
Amazing work with an ATtiny814, only 8KB. Love it.
The distinctive element here is the hardware. Briar allows you to sync via local wifi and bluetooth (i.e. the range is tiny) but since it's a mesh network your message will be relayed eventually.
This device though doesn't seem to support mesh connectivity because it doesn't have this short range limitation in the first place. It uses a LoRa chip with a range of a few kilometers. The bandwidth is tiny though, for reasons that are both technological and legal. In particular your are asked to respect a duty cycle of 1% (or even 0.1%, depending on the exact frequency you're using). That's 36seconds every hour. On top of that add some cities offer LoRaWAN gateways (between LoRa devices and the internet) and the limits are even more drastic like 10 messages per day, 51 bits being the maximum payload length.
LoRa was designed for async metering of IoT devices basically. This application is pushing it to its limits I guess.
I'm not an expert, I have a couple LoRa chips but never used them, however here are some back of the napkin calculations:
Assuming a spread factor of 12 (very long rage, very low bandwith) and a 1% duty cycle, you can send about 40 messages per hour if they are short like "yo what's up". 50 chars -> 20 messages/hour. 100 chars -> 10 messages/hour.
Does the duty cycle mean it's only sending a receiving for those 36 seconds of every hour? The hermit in me is enthused by communicating with this restriction.
IANAL/IIUC, it can also be, e.g., 10ms every 1000ms, and it only applies to emission side of it. You don't have to actually put away the device for an hour after picking up once if the modem is not sending 36 seconds straight. But it does divide the data rate by 100.