New LoRa RF distance record(thethingsnetwork.org) |
New LoRa RF distance record(thethingsnetwork.org) |
However sometimes you can get Troposheric propagation on these high frequency bands. This used to be common when I was a teenager living in the south of England in Kent and we could occasionally receive racy TV channels from Europe.
https://en.wikipedia.org/wiki/Tropospheric_propagation
From wikipedia:
> Tropospheric propagated signals travel in the part of the atmosphere adjacent to the surface and extending to some 25,000 feet (8 km). Such signals are thus directly affected by weather conditions extending over some hundreds of miles. During very settled, warm anticyclonic weather (i.e., high pressure), usually weak signals from distant transmitters improve in strength.
Radio Amateurs love this kind of propagation. It is very variable, doesn't last long, but can give you contacts over great distances on frequencies which are usually line of sight. I think the record for radio amateurs on the 70 cm band (430-440 MHz) is over 4,500 km!
No, LoRa can run on two bands in Europe, either EU433 from 433.05 to 434.79 MHz or EU863 from 863 to 870 MHz.
See e.g., https://www.everythingrf.com/community/lora-frequency-in-eur... or https://www.thethingsnetwork.org/forum/t/is-there-an-agreed-... or for a more dense, but definitive source https://docdb.cept.org/download/4316 ("EUROPEAN TABLE OF FREQUENCY ALLOCATIONS AND APPLICATIONS IN THE FREQUENCY RANGE 8.3 kHz to 3000 GHz (ECA TABLE")
Albeit I'm not sure what band they used here.
All of this has really nothing to do with LoRa and everything to do with physical properties of the emissions (frequency, power, polarization) and physical properties of whatever happens to exist in the world at the time.
So, any physics people here care to comment how this works? Is this pure atmospheric refraction or is there something else?
[0] https://www.camras.nl/en/blog/2021/first-lora-message-bounce...
> providing a standardized and objective measure of the technology's capabilities
Not really. The environment is still variable. A short message could have bounced off some random short duration reflector somewhere (aeroplane, meteor, lightning, ...) or have been refracted by some short term effect. Standardised and objective is an anechoic chamber or a cabled in attenuators/channel simulator.
From what I gather, the map says a "SF:12" which means a spread factor of 12, at a bandwidth of 125khz. With a code rate of '1' according to https://www.rfwireless-world.com/calculators/LoRa-Data-Rate-...
this means about 292 bits-per-second transmission rate for the packet. But I'm unsure if this is correct.
How hard would it have been to put that in the post? I feel like there is some conspiracy to never talk about bitrates/transfer rates in the LoRa world. Like, ever.
Just say it. It helps people understand what this tech is for.
On that point, have you looked at Myriota's research? (https://myriota.com/) In developing their system they went right back to the fundamentals and reworked everything around the idea of short messages. For example, an implicit assumption in the Shannon bound is that the message length is long, so they figured out that their short message system doesn't obey the Shannon bound and designed the coding and so on accordingly. It's fascinating stuff if you're into information theory.
maybe not mentioning the bitrate discourages misappropriation?
Literal-minded people are an endless source of joy.
ExpressLRS has taken everything by storm, partly because it's a well-governed open source project, and it manages to innovate many times faster than the old companies manage to fix bugs in their own products.
At this distance you need a 130km-high tower for line of sight due to earth’s curvature. The previous record was set on a balloon flying at 38km height. LoRa uses high frequencies so shouldn’t benefit from the ground effect?
On VHF/UHF it's usually atmospheric ducting where radio signals are getting reflected between two layers of air.
There isn't any opensource modulation scheme that comes even close to LoRa.
Not until it becomes widespread. For-profit companies are not charities and they patent things for a reason.
No, to be honest: Very impressive. It's kind of a "dream" of me, to bring Internet to the river/picknick area two kilometers away from me. LoRa would probably be the way to go, will have to look further into that.
(Fwiw I wasn't the one who downvoted but thought it'd be worth mentioning)
https://www.youtube.com/watch?v=hMOwbNUpDQA&list=PL3XBzmAj53...
1. How to increase range: https://community.emlid.com/t/increasing-lora-s-range/32597
2. LoRA repeater: https://hackaday.com/2019/05/02/simple-self-contained-lora-r...
3. High altitude LoRA receive-transmit: https://www.daveakerman.com/?p=2828
I've had a plan to blanket my city (Vienna) with LoRa and create my own local Internet, wiring up only retro computers .. seems like its time to break out the ol' lunchboxes and get cracking.
Or just you know, use the 4G that is probably there already.
Yeah... Projects like open WiFi are probably becoming less and less useful, as everybody is carrying 4G/5G modems in their pocket.
They're referring to this:
There's more differences but those are the ones relevant to this discussion.
A different, low resolution internet basically. But LoRA is too slow for a lot of things. Too.
Still nice.
For some reason, I don't find LoRaWan at all alluring. As far as I can tell, in the end it's in the hands of one company and that really defeats the spirit for me. I mostly just use LoRa for point-to-point connections with my own shitty networking stack.
(For those that don't know duty cycle limitations: https://www.thethingsnetwork.org/docs/lorawan/duty-cycle/)
Who knows, maybe we will have a retro- net up and running in the next few days ..
As an aside, would radio via the moon ever be practical? Without pumping out so much transmit power that you pick up the signal anyway, without pointing a receiver at the moon. I think it would be neat, if only for the sake of novelty.
Here's a C program with the correct equation.
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main(int argc, char **argv)
{
double d, f, lambda, loss;
if (argc != 3) {
fprintf(stderr, "usage: moon <km> <frequency(MHz)>\n");
exit(-1);
}
d = atof(argv[1]) * 1000.0;
f = atof(argv[2]);
lambda = 299792458.0 / (f * 1000000.0);
loss = (0.065 * (1.738e6 * 1.738e6) * (lambda * lambda)) / (631.65468167 * (d * d * d * d));
printf("EME path loss = %f dB\n", 10 * log10(loss));
return 0;
}
Satellites make moonbounce impracticable.