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Walkie-Textie Wireless Communicator

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Re: Walkie-Textie Wireless Communicator

#11

Post by pastorhudson »

etrautmann wrote: post #6
patwolf wrote: post #4

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.

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.

Re: Walkie-Textie Wireless Communicator

#12

Post by [deleted] »

sejje wrote: post #7
etrautmann wrote: post #6

Earlier quoted context omitted.

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?

You need a ham license to do most anything with a Baofeng legally.

[deleted]

Re: Walkie-Textie Wireless Communicator

#13

Post by jpalawaga »

threemux wrote: post #10
patwolf wrote: post #4

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 removab…

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.

Re: Walkie-Textie Wireless Communicator

#14

Post by kingkawn »

sejje wrote: post #7
etrautmann wrote: post #6

Earlier quoted context omitted.

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?

You need a ham license to do most anything with a Baofeng legally.

Not true, GMRS licenses are much easier to get

Re: Walkie-Textie Wireless Communicator

#15

Post by kingkawn »

clbrmbr wrote: post #8
Tepix wrote: post #2

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.

Receipt for LoRa is low power, its transmission that kills the battery

Re: Walkie-Textie Wireless Communicator

#17

Post by gausswho »

Xmd5a wrote: post #9
guerrilla wrote: post #3

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 rea…

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.

Re: Walkie-Textie Wireless Communicator

#18

Post by hackcasual »

kingkawn wrote: post #16
lrvick wrote: post #5

If you want something like this with asymmetric encryption, a qwerty keyboard, mesh range extension, and a GUI, try a T-Deck running Meshtastic.

Or get a rak device that has a better antenna and range than the T deck

Oooh, which one has a keyboard?

Re: Walkie-Textie Wireless Communicator

#19

Post by tonyarkles »

clbrmbr wrote: post #8
Tepix wrote: post #2

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.

Re: Walkie-Textie Wireless Communicator

#20

Post by arghwhat »

kingkawn wrote: post #15
clbrmbr wrote: post #8

Earlier quoted context omitted.

LoRa is actually pretty thirsty on receive. You’d need some scheme for synchronization if you want to reduce power consumption.

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.

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