Excellent explanation of a whole range of radio concepts all in support of describing just how LoRa on 2.4 GHz can travel much farther than WiFi or Bluetooth on the same frequency.
Best 15 minutes you’ll spend this month.
- Frequency
- Penetration
- Modulation including AN, FM, ASK, FSK, QAM
- Noise and noise floor
- Fourier Transform
- Chirp and de-churp
- RF circuit design
- Diversity
- Open source project
- Drone control
Very cool, I didn’t know ELRS was LoRa.
I wanted to know more about the chirp, this video explains the details well: https://youtu.be/jHWepP1ZWTk?is=nadwHmLyK5TuqtVN .
Yes, that’s an excellent explanation, which is why I shared it 27 days ago 😁
Mind you, to be fair, our instance was having some synchronisation issues which might explain why your post is 42 minutes old, or why you didn’t see mine.
Either way, LoRa is pretty cool.
Wow! Okay that is a really cool video!
I am wondering though, how does the receiver and the sender match their chirping ? On the receiver he calls it ‘internal reference chirp’ but it can be seen on the time spectrum as having a starting point as well; I am wondering how that reference start is chosen?
There is a preamble, which is a known sequence. The receiver uses the preamble to find the timing and frequency offset for the transmitter. In most LoRA-like systems, the modulation parameters are manually configured at runtime, though there is no reason why dynamic payload params cannot be specified in a header. That’s just a bunch of additional complexity these systems try to avoid most of the time.
Starting with a disclaimer, I don’t know, what follows is speculation only.
I suspect that the only requirement is that the slope of the chirp at encoding and decoding is the same.
Ultimately, it’s used to remove noise in relation to a reference level.
I haven’t had an opportunity to do the math to confirm this and I’ve bookmarked a few LoRa videos to see if they get into the mechanics, but I’m not holding my breath.
Edit: This video seems to explain things pretty well.
