So, you thought that machine was airgapped....
Broadcasting LoRa packets wihout a radio [video]
11–20 of 36 posts
Re: Broadcasting LoRa packets wihout a radio [video]
#12This could be very useful as a covert channel on a hacked device, there goes your air gap!
Re: Broadcasting LoRa packets wihout a radio [video]
#13Earlier quoted context omitted.
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 - li…
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..
> 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.
Re: Broadcasting LoRa packets wihout a radio [video]
#14I transmitted this way using a raspberry pi and a basic filter and antenna and was heard one day in New Zealand from Ohio. https://github.com/JamesP6000/WsprryPi
Re: Broadcasting LoRa packets wihout a radio [video]
#15From the github repo:
>Because we rely on harmonics and aliasing, the primary frequency components emitted by your microcontroller are going to be in portions of the RF spectrum where RF transmissions are banned. Please filter your output or perform your tests in an area where you are unlikely to leak significant RF. The overall EIRP output is genreally ≪300uW across the whole spectrum spread out over hundreds of emission frequencies, but there is virtually no way a device deliberately transmitting on these frequencies could ever pass FCC part 15 compliance, even with filtering.
While low over the whole spectrum, on the desired harmonics the power is higher, just how far does it go. I'd also worry about getting into trouble experimenting with such things. Some wilderness areas utilize radio to track and monitor wildlife and resources, hopefully it wouldn't interfere with those. Though maybe it is not easy to get in trouble doing so because of the low power output.
Re: Broadcasting LoRa packets wihout a radio [video]
#16Earlier quoted context omitted.
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 - li…
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 Dyso…
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.
Re: Broadcasting LoRa packets wihout a radio [video]
#17I transmitted this way using a raspberry pi and a basic filter and antenna and was heard one day in New Zealand from Ohio. https://github.com/JamesP6000/WsprryPi
Wow! What were the specifics?
Re: Broadcasting LoRa packets wihout a radio [video]
#18I really liked the explanation of how he used harmonics to get to the frequency he desired. Also, LoRa is really good when it comes to low power data transmission. To share a recent example, with just ~100mW of transmission power, they managed to fly an RC plane to a distance of 100km: https://www.youtube.com/watch?v=CYJ2UOrlXgM .(Their transmitter from the ground station was configured at a higher power, but the tra…
I looked a bit into the LORA protocol. It does offer reception below the noise floor. LORA doesn't do anything to attempt to make other LORA transmissions seem like noise to a receiver that's attempting to lock to your transmission. This makes it possible for a transmission that's closer to the receiver to essentially jam a transmission that's far from it. I guess since LORA isn't used that much, it's not a problem t…
RC stuff (ELRS, Crossfire, etc.) like the parent post mentions mostly avoids this issue by also using FHSS.
Re: Broadcasting LoRa packets wihout a radio [video]
#19I really liked the explanation of how he used harmonics to get to the frequency he desired. Also, LoRa is really good when it comes to low power data transmission. To share a recent example, with just ~100mW of transmission power, they managed to fly an RC plane to a distance of 100km: https://www.youtube.com/watch?v=CYJ2UOrlXgM .(Their transmitter from the ground station was configured at a higher power, but the tra…
Doesn't LoRa have a pretty constrained duty cycle? I read the regs on LoRa (for the US at least) and found that you're required to limit transmission frequency to 1% (36s/h). I'm guessing you'd have to go well past that to operate an RC aircraft in the conventional manner. If you're just commanding waypoints I suppose you could be compliant.
Per channel. Frequency hopping mostly bypasses this issue.
Re: Broadcasting LoRa packets wihout a radio [video]
#20I really liked the explanation of how he used harmonics to get to the frequency he desired. Also, LoRa is really good when it comes to low power data transmission. To share a recent example, with just ~100mW of transmission power, they managed to fly an RC plane to a distance of 100km: https://www.youtube.com/watch?v=CYJ2UOrlXgM .(Their transmitter from the ground station was configured at a higher power, but the tra…
100km @ 100mW is not impressive when it's attached to a 30dBi antenna...
30 dBi means that much reduction from every other direction, unless you're doing active beam forming.
So which directions you excluding?