Hello, today I got my new LoRA modules (SX1278 LoRa Module 433M 10KM Ra-02 Wireless Spread Socket) from ebay. I want to build a project with them in order to learn. Do you have any suggestion of something that I could build with them? I am thinking of something new so as not to get involved with old ideas that have already realized in the net. I will use Pro Mini ATMEGA328P 5V/16M.
So the question really is: what can you do with a very low data transfer rate that has not been done before?
Depends entirely on what you are intending to do.
As a benchmark at 10mW and at a date rate of 10,000bps, a low cost LoRa device will cover more that 100km using simple antennas under line of sight conditions.
Can 10mW reach 100km? :o even at a LOS???
LoRa is able to receive signals below the noise floor...
wvmarle:
LoRa is able to receive signals below the noise floor...
So, how can it separate the noise from the signal?
alex5678:
So, how can it separate the noise from the signal?
Some very clever math is involved - which as far as I know is a trade secret of Semtech, and otherwise would no doubt be way over my head. Part of the trick is in the spread spectrum transmission they use.
The HopeRF datasheet of their RFM9x LoRa modules claims a sensitivity down to -148 dBm, and a SNR of as low as -20 dB.
But the most important thing: it actually works! There's a report of transmitting over a distance of 702 km using a weather balloon, but they used a bit more power than that 10 mW: their transmitter produced 25 mW.
alex5678:
So, how can it separate the noise from the signal?
It uses spread spectrum technology, in much the same way as GPS receivers do. There are some notes on the link below;
wvmarle:
The HopeRF datasheet of their RFM9x LoRa modules claims a sensitivity down to -148 dBm, and a SNR of as low as -20 dB.But the most important thing: it actually works! There's a report of transmitting over a distance of 702 km using a weather balloon, but they used a bit more power than that 10 mW: their transmitter produced 25 mW.
Well yes, but the so called sensitivity is lab based or was measured out by Pluto.
In the real World the RF noise floor is the limiting factor, and a typical receiver will be seeing circa -105dB of noise. When you test for real with a LoRa spreading factor that operates at -10dB below noise you will find comms fails when the signal strength seen by the receivers is circa -115dBm, even though the datasheet claims a sensitivity of -131dBm.