[FrankPetrilli]

Notably, Wez's flight was done with 2.4GHz LoRa (this was one of his main points, to address naysayers who claimed a 2.4GHz link could never achieve >100km) while Charles is using 900MHz - the same setup that achieved 100km (100mW with a lightly directional antenna on one end, ExpressLRS 50Hz RF mode) would have a theoretical range of >500km on 900MHz. LoRa at longer wavelengths can achieve some incredible feats - like microwatts or nanowatts of power to >1 mile as we saw here. :)

[jorvi]

Were the naysayers saying 2.4GHz was impossible at all, or were they saying in a normal setting?

The distinction is quite important because I imagine anything bigger than the tiniest of villages will be swamped with interference..

[FrankPetrilli]

In particular, people used to plain FSK RC protocols like Spektrum DSM, FrSky D8, Futaba FASST, and similar which tend to failsafe around <1km even with 100mW of power believed that a 2.4GHz link could never do 100km regardless of interference or noise issues.

Also notably, LoRa does tremendously well with real-world noise and interference. Of course any receiver is susceptible to frontend overload, but in "normal" situations I never worry about flying 2.4GHz even in crowded cities, and have never had a failsafe even in some ridiculous situations. As someone above mentions, LTE on the 800MHz band with 900MHz control links are much more of a problem - I've had a failsafe for that exact reason at <200m total distance from takeoff.

[jorvi]

Damn, that's quite impressive. Thank you for clarifying!

[topspin]

> Were the naysayers saying 2.4GHz was impossible at all, or were they saying in a normal setting?

The naysayers, even if they aren't strawmen, weren't "saying" anything of note. There aren't any mysteries or questions here: what can be achieved is predetermined by the factors involved. The key figures of merit are power, gain, path loss, noise and receiver sensitivity. Whatever those factors are determines feasible range, and they are all well understood.

[api]

Should we be looking for evidence of LoRA style transmissions for SETI? The energy required to get a loud conventional signal to go dozens or hundreds of light years is insane. But it seems like this kind of modulation might allow interstellar range with “only” gigawatt scale power levels.

It’d be an ideal way to create a signal with the potential to reach, say, a large fraction of the galaxy without requiring a Dyson swarm to power the transmitter.

Of course there are so many modulations this might be combinatorially impossible unless we can make some rational guesses about what a rational intelligence would use for interstellar communication if they wanted others to notice.

[wildzzz]

You get added again out of a spread spectrum signal and it helps with interference too but the main issue is that with the power spread out, it's much harder to detect at long distances. It becomes even harder to detect when you don't know the spreading sequence. You may "see" some RF power in the spectrum but without knowing the chip sequence, it might as well be noise. LoRa uses a type of spread spectrum method that is even harder to detect if you aren't expecting it. There's an example of someone using it for a 100km data link for an RC plane but you know what works at an even longer range? CW, aka Morse code, at low frequencies (1-30MHz). They can wrap around the earth even at relatively low power. LoRa is nice because it's modern and you can get nice data rates that are appropriate for machine-to-machine communications but spread spectrum waveforms will never be useful when you just want any signal to go as far as possible.

[saidinesh5]

Yeah.. but with 900Mhz won't there be a lot more interference from 4G towers though? I remember there were a bunch of "Crossfire failsafed near a 4G tower because i chose the wrong region" videos.