Walkie-Textie Wireless Communicator
technoblogy.com
technoblogy.com
There is no resend or reliability in the message sending. If it fails you must retype it. I can't remember exactly if it even indicates it fails? I remember testing with two devices, one in a faraday to test bad conditions.
In the end they got salvaged for parts from my kids for other projects.
The goal was to have a simple backup/emergency communication device and get to learn about LoRa. Not sure which other devices I will try but definitely know more what to look for now.
You must be mistaking this design for another one. This one was released only a few weeks ago, and specifically offers LiPo batteries:
"The PCB has space for a 2-pin JST socket that will allow you to plug in a standard LiPo battery, such as the ones supplied by Adafruit."
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.
On 868MHz with standard 5dBi omnis.
Thesis: as long you are using one of the more robust LoRa settings it always will work as long you have LoS or at least only lightly obstructed LoS.
A robust communication needs to work in valleys
However, in EU there is a legal limit of 1% duty cycle on 868MHz band and collision avoidance mechanism, meaning on average you can send a packet (up to 255 bytes) once a minute.
A G2 Basestation or rak device is ideal for node to node communication to act as a base station for range extension.
People interested in LoRa may also be interested in 802.11ah, or Wifi HaLOW
Thanks a lot I wasn't aware of this technology. Turns out you can already buy gateways and boards/modules, and it seems it wasn't the case last year.
Any tip on how I can power these things wirelessly ?
See, for instance
The major upside is transmit power and the downside is not being able to use encryption.
[0] https://meshtastic.org/docs/configuration/radio/user/#is-lic...
So if you like, get a license, crank transmit power, then use encryption all you want and don't worry about it.
It will be enforced about as fast as movie torrenting.
This is all deployed by hams down to around 1 cps, by the way (js8call.com).
https://www.cnx-software.com/2025/08/12/lilygo-t-lora-pager-...
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.
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, 1 bit per 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 hundred bits a second of whatever. I admit it's a solution somewhat in search of a problem. Weather updates? Emergency alerts?
Dim memory from my Ham Radio days that you’d need an antenna length of 1/4 the wavelength, which wouldn’t be very convenient for portable devices, unfortunately.
Many wristwatches are capable of receiving these LF time beacons, despite usually having antennas more compact than several kilometers.
For example, the German LF time signal, DCF77, dedicates some of its "spare bits" to broadcast civil protection and weather forecast information, the latter of which many simple LCD "home weather station" thermometers can receive and decode.
GNSS (navigation satellite systems like GPS or Galileo) are also an obvious candidate for this, given that essentially all phones already can receive their signals.
I wish the hardware was included directly in the phone. It would be super useful for outdoor activities where there's no cell service and you often end up just out of yelling distance.
It's next week, so unlikely to happen and I'm not sure what technology I would need to make it all work. Something like Lora plus a way to make the phones work.
Outside of the legal realm there are also ham radios that are either easy to frequency unlock or are pre-unlocked to do FRS+DMR for encryption though I would never do this outside of a dummy load.
Back in the day we would "find" spools of phone cable and string them between houses. If you found that much cable you could definitely wire up a few miles of woods.
Hook the speaker and mic up to the phone part, wire the hang up switch or rotary pulser to the musical tone button.
The ring might be a little quiet but this would be real easy to setup quick.
Currently we're working on a new wireless modulation that has much higher bandwidth (similar to HaLow) but 1000x better in BER performance than LoRa in limited LoS propagation model based on simulation. If we can get 100x improvement in real world testing for the high bandwidth version I'm more than happy. Our Japanese collaborators has tested the lower bandwidth version similar to LoRa bandwidth and frequency, and it work fine inside a bunker.
If you're interested perhaps we can collaborate on testing the solution. Already proposed to IEEE as new wireless PHY modulation but to no avail yet.
And I got like 3km range in my city so it was great !
But then I wanted to make it a ""usable"" thing and started getting stuck on designing a protocol that allows multiple senders at the "same time".
I thought of doing a time slice system since this whole project was inspired by a telecommunications class I had, but the issue would be that people you would need to know in advance the number of slices and your assigned one and also the devices would have to be synchronized, and I really wanted to make it dynamic, do anyone can just turn on their thing and it does a sort of handshake until everything works.
If anyone has pointers It'd be very appreciated, I found out about meshtastic.org while doing this project too.
In the end this was my first embedded experience, and my first embedded with Rust, so at least I got something "working" but I would love to make something as "usable" as this post.
How would you propose that those messages get routed if there is no connection to either the internet nor a cell provider?
Nothing preventing you from configuring a local SIP server or doing IP-to-IP calls, though. I think every platorm imaginable has some kind of free SIP client.
Here a quick search: https://www.reddit.com/r/sdr/comments/1bn1n5f/how_to_run_ope...
Legally? No. But it's totally possible.
There are micro-towers for cell phone testing you can buy and cell phones think it's a real tower. Law enforcement uses one of them to track criminals IIRC.
But it's very tightly regulated.
However, it uses GMRS bands, not LoRA, so all the FCC restrictions apply.
If you want to use GMRS, buy a GMRS radio.
Actually, no ham radios that can transmit on GMRS bands are legal (in the US).
See 47 CFR 95.1761:
https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D...
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.
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.
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.
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.
You’d need some scheme for synchronization if you want to reduce power consumption.
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.
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.
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.
With the walkie-textie type system you're making a different tradeoff here though that would have to be measured and assessed. Now you've got a couple of knobs to twiddle with:
- What's the max acceptable latency between sending a message and receiving it? That determines your beacon interval and becomes the factor that determines your battery life (effectively your Rx duty cycle + Tx beacon energy).
- Does transmitting the beacon at your beacon interval and only having the receiver run in a limited window around that beacon result in a larger or smaller net power consumption? That's going to depend significantly on your transmit power vs. receiver power.
On 868Mhz you get 36 seconds per hour or even 3.6 seconds per hour.
Depending on your power usage sending may also be very slow.
Then again, the primary user of 434MHz is actually amateur radio, on which you can operate beacon transmissions if you care to!!
Amazing work with an ATtiny814, only 8KB. Love it.
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.
Why do people still use these ancient chips?
The RP2350 is the same price and several orders of magnitude more capable for example.
Really though, how many of these is he making? 3? Cost isn't a factor.
I think this just comes down to philosophy. ARM gives you a way richer tool-chain… and you need it. The complexity to do anything skyrockets. You have a compiler in the loop so achieving deterministic performance is much more complicated... not to mention caches. The tooling for doing statistical analysis is infinitely better; but just sitting down with a pencil and doing static analysis will always be both simpler and more accurate. For cases where you're writing thousands of lines, I too will generally prefer ARM -- but if you're just writing a couple hundred instructions, assembly is just less to think about.
Similarly philosophical is "more capable" -- an RP can handle many more use cases, I agree, but if both handle a given use case, with the same quality, then neither is more capable /for that use case/. And the one that achieves that use case at quality with the simpler implementation is, in my philosophy, preferable.
Also, while there are equivalents to the CCL in other processor families, it's by no means universal; and it's not at all rare that the CCL saves one or two external chips.
I'm looking forward to seeing a LoRa texter that's several orders of magnitude more capable /i
Perhaps you're confusing it with the older ATtiny841 (released in 2012), which was an upgrade of the original ATtiny84.
If you get into deep shit, some amateur FM handy-talkies are IMHO more likely to be able to get you help. Or perhaps T-Mobile's T-Satellite service if you are headed somewhere really remote.
Unpopular opinion: Meshtastic is a solution in search of a problem.