@bob @h @wakest One area of research I want to get into once I get a viable Kestrel Computer platform is free-space optical networking. There's RONJA which predates me, but its range is limited (by necessity; the farther out you go, the more amplification you need on the input stage, which means higher impedance on the LNA. Coupled with the capacitance of the photodiode array, that drops input bandwidth *fast*). Free-space optical is a prerequisite in my mind for true grass-roots networking.
@h @bob @wakest You can go sea-level to the moon if you want. The trick is to NOT USE LASERS, as everyone is so keen to do. Lasers decohere almost immediately as soon as it hits any particulate matter in the air, or has nasty diffraction effects in weather cells. A *fat*, incoherent tube of light works a lot better (that's why lighthouses work so well in stormy weather). Audio bandwidths have been communicated up to 230+ miles on a single link this way.
@wakest @bob @h I should point out that the reason the bandwidth was limited to a single AF channel is because of the time-constant effects between the photodiodes and the high impedance of the LNA, which combines to make a low pass filter. If you can work around that, your bandwidth can be improved markedly.
I have some ideas on this front, but I need the time and equipment to play, hence one of my private motivations for my Kestrel project. :)
@h @bob @wakest Some inspiration for consideration: http://modulatedlight.org/optical_comms/optical_index.html
Audio as in ultrasound, I assume?
What would have to be the power of the ultrasound signal?
You enter a territory marred with medical concerns due to the biological implications if you're going to use these networks in a space where humans, animals, and other living things exist.
@h @bob @wakest You're not understanding; it has nothing to do with wired or wireless. :) The issue is the receiver's *amplifier*. With greater distance, your received power drops off with the square of the distance. So the further away your transmitter, the greater amplification you need to recover a usable signal. (In a wire, you have Ohmic effects which degrade the signal; in free-space, it's just normal optical effects and scattering).
@wakest @bob @h To amplify incredibly weak signals, you need enormous gains, on par with a radio telescope in fact. The input impedance for such an amplifier must be very high, tens of megohms at least, so as to not put load on the receiving transducer (a photodiode in our case).
The photodiodes themselves are operated in a reverse bias, which means there is actually a degree of capacitance to them, measured in nanofarads. If you multiply 1nF * 1 Mohms, you get 1 millisecond, which means 1kHz
So, let's see if I follow you. You're saying that the optimal frequencies to transmit *and* receive are in the audio range (humanly audible frequencies, from 20 Hz to 4 Khz). You're saying that free-space is better to avoid Ohmic effects.
I'm trying to understand what medium and environments would match the ideal conditions you think would be workable.
@h @bob @wakest It's not that there is one preferential bandwidth; it's a function of distance. (It's also why you can't get DSL service beyond a certain radius from a telco). The further out you go, the slower the link. The closer you are, the faster you can push it (you can get by with lower impedance amplifiers at the front-end of the receiver). RONJA gets 10Mbps (literally, it's 10-base-2 ethernet over optical!). But it won't cover a 200+ mile distance at those speeds.
What would the medium look like?
What would be the ideal setting?
Drastically varying density of populations means that in different segments you need to optimise for different needs. Connecting two towns separated by 100 miles is not the same as connecting two neighbours separated by a few blocks.
@h @bob @wakest So, you would need a line of sight from point A to point B, obviously. Otherwise, you'll need some kind of repeater station to overcome the shadow created by the intervening obstrction.
That said, assuming you have line of sight, a 100 mile link can probably be bridged with a single transmitter on one end, and a receiver on the other. Each would be about the size of a 15" SONY Trinitron monitor (mostly empty space for the optics required), and they'd face each other.
I think that this is the kind of project that would require a very well defined product that is relatively less DIY in which many people can participate with minimal knowledge.
Say, three different types of kit usable at different ranges.
The people inclined to do the harder work linking cities and towns may sometimes not be technically oriented, they could be non-technical activists bridging working groups together.
Considering what's possible is exactly what we were doing.
I was replying to Sean who suggested that everything exists already because ham radio users have been doing it for ages, which is missing the whole point.
Making it a workable product for adoption by non-radio-people is the whole point, and as you're aware, an entirely different kind of job.
I wouldn't trivialise it saying it's just productisation. It's work that hasn't been done, work that somebody has to do.
I'm frequently confused here too. The limits of the medium become apparent when you use it anyway, that's not a bad thing.
Maybe something that will be alleviated using a forthcoming Mastodon client that does threading better.
Someone showed me a GUI that did display Mastodon threads as a tree graph. It was an interesting experiment some months ago, perhaps I should look again into it.
I am aware that radio exists and that people use it for things.
You may have missed some earlier toots.
I'm not trying to discover radio waves, I'm trying to find a different ways of applying already-existing tech.
Different uses have different constraints and require different ways of delivering a product that works for specific purposes.
We were discussing something different, not ham radio, which I am already well aware it exists.
Maybe read what we discussed earlier?
The idea is to reuse existing software, and *adding* on top of that. Then integrating tools it in such a way that it helps control, routing, QoS handling, etc. so that the *goal* of assembling co-op operated networks and ISPs becomes easier or hopefully trivial work in the future.
This is *not* ham radio. This is a different application of radio, and existing software.
Sorry, it's just that maybe you should assume that the people involved have a basic level of understanding of these things.
Whilst we may not remember the exact name of the software packages, we have known that digital information can be transmitted as audio for decades.
I understand the enthusiasm and spirit that motivates the urge to contribute and that can't be a bad thing. Please consider that frequent derivations can be distracting from the focus of the discussion.
@h If you really cared so much about avoiding distraction you could have simply not responded. But correcting people who might have made bad assumptions about your knowledge or what you meant seems to be more important to you than avoiding deviations from the core discussion.
@wakest @h @bob I've historically also been a fan of token-ring networks, if for no other reason than the fact that it achieves 90% efficiencies effortlessly. They're not as useful in a LAN situation, but for a backbone, they'd be great. A mesh network is theoretically great for hauling a lot of data, but in practice, I'm not so sure. Maybe 50% at best. Any real-world network will likely be a combination of the two, especially as usage scales.
@bob @h @wakest There's another issue, which is that people expect to reach the services they consider "the Internet" (Facebook, Twitter, Instagram, whatever). There are no transparent FOSS workalikes out there, which means people don't use them. This also means negotiating uplinks from the mesh to the public Net... which means running right into de facto censorship.
Also, fucking Android...
More poignantly, mesh networks collapse under their own weight once you grow the network beyond a certain inflection point. Link maintenance overhead starts to dominate traffic, and you get diminishing returns after that. Network partitions will become frequent under even moderate load.
And we know there'll be load from spammers.
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