Latest Raspberry PI and Meshtastic

Good day to all,

This is my first msg here. I live in Morges ( Vaud ).

I am doing my homework - first on paper, now ready to order hardware -, planning on setting up a sensor connecter to a Raspberry 5 to send a 50 characters string every second through a Lara transmitter to a Lara receiver connected to a windows PC, 24 hours a day.

I am planning in the future to use it in a large area with a high number of those. My money being limited, I’d rather go for the right one from the very first time :slight_smile:

I have been doing some research on the Net, and I found many different Lara devices. But since I intend to use a GPS, it looks like that the LILYGO TTGO matches those requirements.

My questions are :
1- could you please confirm that this is the right choice, and that this toy can stay up and running 24 hours a day ?
2- Should I plan for a cooling system specifically for that transmitter ?
3- I can 3d print but by experience I know that printed plastic does not like the sun. Would you know of any ABS enclosure which could hold both the raspberry 5 and the transmitter, taking apart the antenna for not resonating outside of the planned range ?
4- According to your experience and due to the ground mineralisation in Vaud, would you rather go for 433 or 868 MHZ ? I have used 433MHZ already for DIY drones but I have never played with 868MHZ ?
5- Do you have a favorite supplier in CH, passionate and knowledgeable about that transmitter, and ideally also selling the Raspberry 5 ?

Thank you so much in advance


  1. In general yes. Certainly if connecting to power, rather than battery.
    … one thing to be aware, most location have ‘duty cycle’ restrictions even on the ISM bands. So might have to be careful of transmitting too regually.

  2. Very unlikly to be needed. Lora is very low power compared to (most!) other RF solutions. Can vary the transmission power, but unlikly to be going over 150mW with consumer devices like the above.
    … would get very warm in direct sunlight. But probably wont be a problem.

  3. Dont know.

  4. Lots of subtly, but think the general rule us 433 gets slightly better building penetration. But 868 better bandwidth (due to higher frequency) and better long range use.

  5. Nope. But will say really like components. Used their lora boards, and their basic 868mhz antennas are reasonable. Although I have only used the RP2040 devices, and haven’t tried them with meshtastic yet (would need custom firmware)
    (so might be a little outside your scope, if wanting GPS+Meshtastic)

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Thank you for those answers.

Now having built drones a long time ago with little 433MHZ units for telemetry, I just recall that antenna orientation was very important and that GPS should also be as far as possible from both the antenna and the processor.

Any recommendation about a quality distant antenna and a quality distant GPS please ?

To be honest, not seen any issue of interference. But only tried a few devices. (have used ilabs challenger with a connected GPS, transmitting telemetry over lora. And seperately some heltec trackers with meshtastic)

Lora is rather ‘bursty’, ie very short spariodic bursts of transmission.

Wonder if the drone telemetry, was effectify continuously transmitting. Whereas with Lora, will be quiet times for GPS to work ok.

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Interesting post about 868MHZ antenna comparison, resulting in a surprisingly cheap winner.
I personally used the #10 on long distance drones a long time ago, it was very good, but due to drone itself changing position and balance while our installations are mostly fixed ( could be drones too actually :slight_smile: )

I live next to you, please don’t spam the frequencies.
On top of that there is the 10% limit that you would probably blew.

That is a nice and warm welcome thank you.

Nevertheless, this is a good point.
If sending, say, 50 octets every second so 180 kilo octets is considered like spamming by more just one individual then indeed that network is not the right one for me, I’d better built and place my own Lora repeaters and members.

So how much volume of octets by the hour is or is not acceptable on Meshtatic ?

Where is the threshold ?

Would one 100-caracter msg every10 seconds, thus 36k be below that threshold ?


didn’t mean to sound unwelcoming, but you arrive with your 1message per second, without having gone through the doc that explains the duty cycle that would clearly prevent your project to work.

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That is why God invented data buffers, heavily used at the beginning of Internet when I was paid to work with 9600 bauds modems

The EU regulations says duty cycle at 868 is 1% so half a second every minute. Neglictible.

Fair behaviour rule of thumb mentions 30 seconds air time per hour for uplink. That is a lots of data.

So in theory I would be using a tiny portion of the network.

But that is pure theory.

So the question is ( I am asking before because I try to be polite ) :
in reality, what numbers do you see ?

What is the transmission time ?

How many milliseconds are 50 characters taking to be transmitted ?
In. Slow mode and in Fast mode ?

How much data is spamming ? Again, where is the threshold ?

As long as you back your arguments up and provide information and numbers, you can be as unwelcoming as you wish, I don’t mind

In general I dont suppose Duty cycle will be too much of an issue. (as mentioned packets is sent as a databurst)

a SDR is a good way to measure transmission times

But there is also a offical Lora calucaltor LoRa® Calculator | Semtech will give something like “Time on Air: 25.63 ms”
will have to match the settings to the preset used
Radio Settings | Meshtastic
Above was using US MediumFast.

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Love your answers. Much appreciated. Thanks.