I would have loved this as a kid. Walkie-talkie range and battery life made them useless for my adventures.
Walkie-Textie Wireless Communicator
81–90 of 130 posts
Re: Walkie-Textie Wireless Communicator
#82Earlier quoted context omitted.
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 transmissi…
>not all ham radios that can transmit on GMRS bands are legal to do so.
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...
Re: Walkie-Textie Wireless Communicator
#83Earlier quoted context omitted.
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…
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. There…
Yeah I've actually built a system like this before. The nodes didn't have power supplies with strong storage capacity but did have an infinite source of limited energy harvesting (they could extract a tiny amount of power from the environment they were monitoring).
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.
Re: Walkie-Textie Wireless Communicator
#84Very nice. I'd like to see one like this that uses frequencies that can pass through 200m of rock. Obviously the radio frequency will need to be much, much lower (https://en.wikipedia.org/wiki/Through-the-earth_communicatio...). Why, you ask? Cave rescue situations.
Re: Walkie-Textie Wireless Communicator
#85Earlier quoted context omitted.
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, building…
Some countries already do this! 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 rece…
Galileo already has search and rescue (SAR) and emergency functions (EWSS)! GPS is trickier, as it's still sort of a millitary-first platform.
Re: Walkie-Textie Wireless Communicator
#86Earlier quoted context omitted.
What's the data transmission rate with the balloon, put of curiosity?
Hard limit is 3.5kbps with 148dB link budget (Medium Fast preset in Meshtastic [1]). In practice - a packet worth of hundred bytes every half a second or so. [1] https://meshtastic.org/docs/overview/radio-settings/
Is that the cap of the whole system or can multiple users use it with individual caps of 3.5kbps? That's somehow both faster and slower than I expected.
Re: Walkie-Textie Wireless Communicator
#87I'm backwoods camping next week, and we have 25 people spread out over three sites. I was thinking it would be funny to bring some old rotary dial phones and some sort of way of hooking them up, and then just have that as the intercom between sites for when dinner is ready or whatever. 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 w…
Cheap FRS walkie-talkies, can find plenty of these on ebay if don't want to buy new (will need new batteries though).
Re: Walkie-Textie Wireless Communicator
#88Earlier quoted context omitted.
Or get a rak device that has a better antenna and range than the T deck
Oooh, which one has a keyboard?
t-deck has a keyboard and is ideal for a personal handset.
A G2 Basestation or rak device is ideal for node to node communication to act as a base station for range extension.
Re: Walkie-Textie Wireless Communicator
#89[deleted]
Re: Walkie-Textie Wireless Communicator
#90Very nice. I'd like to see one like this that uses frequencies that can pass through 200m of rock. Obviously the radio frequency will need to be much, much lower ( https://en.wikipedia.org/wiki/Through-the-earth_communicatio... ). Why, you ask? Cave rescue situations.
It's not only lower frequency, it also need robust wireless modulation that can work with very limited LoS where LoRa perform badly. LoRa is pretty much useless in your use cases.
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.