Correct. The LoRa configurations mentioned which offer 100× the speed of Meshtastic/Core operate at 800 kHz and 1.6 MHz bandwidth, which are permitted by the FCC in 15.247.
As far as I know there's not actually anything particular to 2.4 GHz allowing higher throughput for LoRa than that the corresponding Semtech chip happens to support wider bandwidths. (I.e. no legal barrier.)
The tradeoff is less range due to lower link budget. Doubly so because 2.4 GHz has higher free-space path loss. You're not going to get outside your house with these speeds. The primary use (as stated in the original post) is likely through clear space with a directed antenna.
(The 2.4 GHz band is better suited to this use since you can use antennas with higher than 6 dBi gain. If my math is correct, anything higher than 11 dBi is a win even accounting for FSPL and the power derating the FCC imposes.)
At least in Europe the 868 Band is is in contrast to 2.4 allowed only for low duty cycle applications that do not actually occupy the channel for more than 1% afaik (given space multiplexing). I also remember also that the free to us band was quite narrow by design (we built sensor nodes bit banging a PHY transceiver that were in the grey area of unenforced rules, 20 years ago .l)
What issues does it create for others to use too narrow of a bandwidth? Why “should” the FCC care if someone is only using a small portion of the spectrum that would otherwise be fine fr them to use?
The legal power limit in these bands is 1 W. If you spread that out over 500 kHz, that signal is weaker than background noise at any given frequency for anyone more than about a city block away. (Give or take many factors.)
But, if you compress that 1 W into, say, 12.5 kHz (typical for FM voice), your signal is now detectable (and will interfere with other, possibly licensed, users) at over 6 times the distance.
There are probably other factors. For example, it's not legally sufficient to simply reduce your power by a corresponding factor. I suspect it may simply be the FCC's goal to reduce conflict between users by mandating spread-spectrum technologies for unlicensed use.
Note also that 47 CFR 15.247(e) [1] gives a spectral power limit which corresponds approximately with the 1 W max / 500 kHz min specified in (b)(3) and (a)(2).
Final side note – https://docs.fcc.gov/public/attachments/FCC-02-151A1.pdf is interesting reading as to how the current form of 15.247 came to be. Specifically it changed the rule from specifically DSSS to digital modulation generally, which in turn allowed the transition from 802.11b (DSSS) to 802.11g (OFDM) on 2.4 GHz.
The idea with either requiring very wide band or frequency hopping on the 900Mhz band is to make it so that usages of the 900Mhz band 1. are tolerant to some loss (ie: by temporary collision) and 2. don't collide continuously (by using wide band or frequency hopping).
It's a mechanism to try to make the 900Mhz band more useful to uncoordinated users.
There is in fact no photograph of treetops glowing.
There is a digital UV-wavelength video of the corona, and a visible-wavelength video of the trees.
The paper [1] contains a sole picture with tiny circles indicating where the UV-video detected corona events, overlaid over a frame of the visible-wavelength video.
The paper does also contain a video [2] which overlays a somewhat processed version of the UV video over the visible wavelength video, where UV photon events are indicated by decaying red dots.
Do you think they are not photographs of the Sun because these are not what I see if I look at the sun with my eyes? (In which case I'll see pure white then perma black, I assume.)
Sure, a photo taken in non-visible spectrum is still a photo. And stacking photos taken with different wavelength filters or sensor can also be considered a photo. For example the headline image of the spruce tips taken in a lab is photo. And based on the description of the UV camera in the paper, they did generate UV video of the tree tops.
However, the linked article and associated paper don't have any such photos (or video) of the corona in the treetops. Instead the UV video was processed with a detection algorithm, and then the visible-light photos and video were annotated with graphed dots of where detections were seen. Those dots aren't a photo of the corona by any reasonable definition.
While reading I thought this is basically visual tinnitus and then the author used exactly that term. As someone with tinnitus, I can definitely understand the longing for "absolute darkness".
They're the same as looking at the sun with your eyes. You won't go blind looking directly for a short time. It's just best not to stare for a long time.
At work, some guy has been pushing a 2-day feature into its 5th week now, with questions like "what do you mean by (database) table?" "Is <not_a_database_table> a database table?"
Etc...
We have to fill-in RFDs to answer those kind of questions, so the process is massively slow and st...(expunged due to HN guidelines).
So yeah, some people really love their semantics and are willing to do whatever it takes to keep it that way.
[You can take a guess at where this startup will be in 2-3 years ...]
Sorry, in what way is this not a photograph? Are you saying that a video is not a sequence of photographs, that UV photons captured by a sensor don’t count because human retina sensitivity is low in that range, or some hopefully-less-semantic argument?
The headline suggests that people have seen treetops glowing and it just hasn’t been captured on video before. The actual pictures and video is of something that nobody could have seen with their eyes.
This reminds me of a chat room interaction I had maybe 25 years ago. The other person was adamant that humans can't see the infrared from TV remotes, and I was adamant that I could. It was pretty a widespread belief (even in school science books) at that time that humans couldn't see infrared. Since then more science was done to prove that, in fact, some humans can see some infrared under some conditions.
I share that mainly to state that humans are amazing and have a wide and inconsistent range of capabilities (and sometimes even mutating into new capabilities!) Personally, I will always hesitate to say "nobody" and I lean towards "no typical human" instead. :)
The faint red glow is actual red light as many IR LED's (esp the ones used in cameras for night illumination) are close to the visible spectrum and have some visible light emission.
You can absolutely see corona discharge like that with your eyes.
If you come to my day job, and we shut off all the lights in the test room, after your eyes adjust in the dark for a minute, you'll see the soft purple glow coming from the edge our 160kV test rig.
Definitely emits UV, but there is enough visible to see it for sure. It comes from the electrons exciting nitrogen in the air.[1]
> (1:If you come to my day job), and (2: we shut off all the lights) (3:in the test room), (4:after your eyes adjust in the dark for a minute), you'll see the soft purple glow coming (5:from the edge our 160kV test rig).
So, 5 different things that make it glow "not coming from treetops". Parent poster wanted to see glowing treetops in a forest, where we might not be adjusted to dark for a minute.
You can also see such corona discharge with benchtop tesla coils even in lighted room, but those are not trees in forest glowing from a storm.
Even a smallish Tesla coil easily produces voltages north of 160kV. I built one using 4" PVC for the secondary with a wound length of maybe ~2 feet of secondary? From memory of the calculations I did at the time I think it was around 350 kV peak? Might have been higher. Threw 24 inch sparks quite easily.
I don't really blame the researchers here but this is yet another article that is happy to have a clickbait headline which any reasonable reader is going to assume will include a picture of "treetops glowing".
At least personally I scanned the article for it and only found the picture at the top, which I was then frustrated to learn that's just a lab photo, and I came here wondering where the actual image is of it in the field so I found OPs comment helpful to indicate that the suggestion there would be a beautiful picture of glowing canopy somewhere is basically a result of editorializing.
It's true that the image isn't fiction or a purely fabricated "artists rendering" from data. But it's also true that "filmed" and "glowing" are unusual ways to refer to what happened.
You don't usually say filmed when talking about recording uv or microwaves etc. You technically could, and probably back when film was actually how uv was recorded a few people working in the field probably did, but almost no one else does, or no one at all since decades, which means the author of the title is the one out of step, not the people reading it.
They actually recorded something, and this title is misleading. Both things are true.
When I worked in a lab that took videos with a UV camera, I still called them videos, and I would absolutely have said that I took a video of the subject (a methanol flame in this case).
Essentially every color photograph you have ever seen is a composite of a red photographic, a green photograph, and a blue photograph.
I've taken the "captured on film" out of the title above and used representative language from the article. If someone can suggest a better (more accurate and neutral) title, we can change it again. (But the subject is interesting whether on film or not, let alone "for the first time".)
Half of the comments are in this subthread which derailed the discussion on this submission before it even started.
Here the damage is done but maybe, please, refrain from doing so elsewhere.
I am just getting into the packet scene in the Boston area.
APRS aside, as far as I've found, there are about a half dozen Winlink nodes in the area and one BBS. And one lovely node in Cambridge (KZ2X-1 [1]) which provides connectivity to a bevy of ancient (though virtualized) OSes.
I don't know how much AMPRnet activity there is. There are only 7 allocations in the area (mine included). I'd love to be able to e.g. log in to my home network from a few radio hops away but I don't think there's any infrastructure in place for that (such as Mobile IP).
Hah! I was literally about to open up my nascent userland AX.25 stack. Is yours open-source, or would you mind sharing? (My e-mail is in my profile.) I want to get something running on an ESP32-S3. My goal is to turn a Cardputer into a companion TNC console for my Kenwood TH-D74.
It is technically! I sent you an email. It's very POSIX-y, unfortunately, but if you were to make some sort of shim for file descriptors (big ask heh) you would be able to use it just fine.
I have nostalgia for Wario Land, because I played it for 5 minutes in a Toys'R'Us, and it's a good game which I never got to play in full until decades later. But I never owned one, so everything else you said rings true to me.
Never used a Virtual Boy, but I'm somehow nostalgic just for the development tool -- grey metal boxes with vents, LEDs, and rocker switches transport me into an optimistic future of the past.
