Here's a summary of the themes discussed in the Hacker News thread:
LoRa Power Consumption and Battery Life
A significant portion of the discussion revolves around the power consumption of LoRa devices, particularly concerning battery life. While LoRa is often associated with low-power applications, its receive mode can be surprisingly power-hungry. Achieving extended battery life, measured in years, often requires aggressive sleep cycles, waking only for essential tasks or physical interaction.
- Tepix questions the battery life, stating: "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?"
- clbrmbr clarifies: "LoRa is actually pretty thirsty on receive."
- arghwhat explains the necessity of sleep cycles: "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."
- tonyarkles contrasts this with typical IoT usage: "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."
LoRa Power Saving Schemes and Synchronization
To address LoRa's power demands, especially in peer-to-peer communication, participants discussed various power-saving strategies. These often involve synchronized wake-up times and limiting receiver activity to specific, short intervals.
- clbrmbr suggests: "You’d need some scheme for synchronization if you want to reduce power consumption."
- tonyarkles elaborates on the widely used IoT model: "The end nodes can spend the vast majority of the time in deep sleep without the radios turned on... 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."
- IshKebab proposes a peer-to-peer synchronization method: "Each node transmits a beacon once per second. While they aren't connected, each node listens for sub subset of time (say 10%)... 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)."
LoRa Duty Cycle and Bandwidth Limitations
The regulatory aspect of LoRa, particularly duty cycle limitations, was a recurring theme. These restrictions significantly impact the effective data rate and the amount of data that can be transmitted over a given period.
- Xmd5a highlights these constraints: "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 36 seconds every hour."
- Xmd5a further quantifies the impact: "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."
- gausswho inquires about the practical meaning: "Does the duty cycle mean it's only sending a receiving for those 36 seconds of every hour?"
- numpad0 clarifies the duty cycle application: "IIUC, it can also be, e.g., 10ms every 1000ms, and it only applies to emission side of it."
GMRS and Radio Licensing Regulations
A considerable portion of the discussion devolved into the complexities of General Mobile Radio Service (GMRS) and amateur radio (ham radio) licensing, particularly in the US. Users debated which radios are legal for GMRS use, the necessity of licenses, and the restrictions on digital transmissions.
- patwolf mentions a specific device: "For anyone looking for an off-the-shelf solution for wireless texting, I've used the BTECH GMRS-PRO."
- etrautmann seeks clarification: "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?"
- sejje states: "You need a ham license to do most anything with a Baofeng legally."
- kingkawn corrects: "Not true, GMRS licenses are much easier to get."
- wildzzz emphasizes the need for specific equipment: "If you want to use GMRS, buy a GMRS radio."
- 7402 asserts a strong legal point: "Actually, no ham radios that can transmit on GMRS bands are legal (in the US)."
- pastorhudson provides an overview of GMRS licensing: "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."
- threemux raises concerns about compliance: "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."
Alternative Communication Technologies and Platforms
Beyond LoRa, several other communication technologies and platforms were discussed as alternatives or complementary solutions for off-grid and local communication.
- Xmd5a contrasts the discussed device with Briar: "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."
- lrvick suggests: "If you want something like this with asymmetric encryption, a qwerty keyboard, mesh range extension, and a GUI, try a T-Deck running Meshtastic."
- patwolf mentions the BTECH GMRS-PRO, which uses BLE for phone connectivity.
- lxgr muses about integrating similar functionality into phones: "It's a real shame phones don't have something like this built in."
- retrac brings up longwave radio for its exceptional range and penetration.
- password4321 expresses a desire for "push-to-talk over WiFi on my phone interoperable with dedicated devices with no monthly fees."
- RandallBrown mentions Rattlegram, an app that converts data to audio for walkie-talkies.
- f1shy notes that in Peru, operators were forced to offer a similar solution in case of earthquakes.
- pavel_lishin inquires about building a "personal" cell tower for family use without cell service. joshmarinacci replies it's difficult due to proprietary technology and suggests a local WiFi network with IP-based communication. f1shy mentions the possibility of using Software Defined Radio (SDR) for private cell networks, but cautions about legality.
Microcontroller Choices and Design Philosophy
The choice of the ATtiny814 microcontroller sparked a debate about the merits of older, simpler chips versus more powerful modern alternatives.
- IshKebab questions the chip selection: "Why do people still use these ancient chips?"
- addaon defends the ATtiny814: "They're cheap, robust, readily available, super easy to develop for, have a well-chosen set of peripherals that can reduce BOM even further..."
- IshKebab counters: "They have the same price and availability as Cortex M0 chips, are more difficult to develop for (8-bit AVR ouch), and seem to have a similar number of peripherals as any microcontroller."
- johnsondavies clarifies the ATtiny814's age: "The ATtiny814 is hardly an ancient chip. It's a member of Microchip's TinyAVR 1-Series that was released in 2017..."
Nostalgia and Early Wireless Devices
The discussion touched upon early personal communication devices, evoking nostalgia and comparisons to modern iterations.
- kube-system remarks: "Reminds me of what the messenger on the Cybiko was trying to be."
- ljf shares a memory: "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."
- shooker435 wonders: "Whoa, I wonder if I still have my Cybiko Xtreme somewhere."
- jvm___ proposes a fun intercom project: "I was thinking it would be funny to bring some old rotary dial phones and some sort of way of hooking them up..."
- IOT_Apprentice notes a similar concept in media: "They did that on the last episode of Star Trek Strange New Worlds (rotary phones)."
Meshtastic Reliability and Usability
Several users expressed frustration with the reliability of Meshtastic devices, even in simple setups.
- LastTrain reports: "I've tried and tried to use LoRA devices w/ meshtastic for various things, and can't get them to communicate reliably. Even with two devices sitting next to each other."
- loph offers a contrasting perspective to LoRa/Meshtastic: "I'll stick to a walkie-talkie. FRS radios are cheap, easily obtainable, and will work as far or farther than this 915 MHz stuff."
- loph also states an "unpopular opinion": "Meshtastic is a solution in search of a problem."
Input Methods and User Experience
The user interface and input methods for these devices were also a point of discussion, particularly regarding older keypad technologies.
- bluGill warns about RSI from number keypads: "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."
- nullsmack questions the input for the discussed device: "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?"
- triyambakam, referencing devices they owned, notes: "The typing as maybe expected gets tiring. There is no resend or reliability in the message sending."