As my cabin project is slowly evolving from one small shelter to a few tiny structures with the potential to include automated small-scale farming in the future, I was looking at the possibility of connecting them together in some fashion that didn't involve wires. I dislike tech for tech's sake so everything needed a purpose. More importantly, I didn't like the idea of babysitting the network. Writing and enjoying a wood stove flame seem like a better use of my time.
Off-the-shelf access points with open source firmware was the easy choice. Probably those capable of OpenWRT or DD-WRT. The device and antenna would likely need to live outdoors for better connectivity, which means I'd rather have a single wire coming through the walls of the structures. That narrows it down to Power over Ethernet capable devices.
These "connectivity nodes" will then have the following constraints:
- They must be remotely updatable
- They must be powered off-grid
- They must survive exposure to sunlight
- Thay must withstand heavy wind, rain, and snow
- They must be immune to occasional smoke (I.E. from a wood stove)
The last requirement might be particuliar to my situation, but I don't plan on burning a lot of wood. If anything, my own stove experiments have shown that it's possible to be efficient and have a relatively clean-burning fire with properly seasoned fuel and a good stove design.
I would likely have to create my own antenna to get decent reception since most stock devices come with omnidirectional antennas. I probably won't need modify the rest of the device functionality.
The case would probably need to be made of UV resistant resin, transparent to RF, and still durable in the outdoor environment. I'll have to conduct some experiments to see what works.
Meanwhile, I came cross this particular antenna, featured by Andrew Mcneil, that seems relatively easy to make with plain copper sheets. Provided, I use the correct measurements.
I thoroughly enjoy that channel, not just for the information, but his manner of presentation too. Andrew is a bit like the Bob Ross of antennas.
I don't think I'll need the extra elements since I plan on keeping all structures within line-of-sight. I prefer the 2.4GHz frequency range since it's still relatively good in bad weather, even heavy snow.
What I like the most about this design is its solid construction and lack of a PCB. This means I don't have to fiddle with etching to make these and instead, simply cut copper sheets to size and shape. Etching PCBs is always a messy affair, especially with the harsh chemicals involved, and I'd rather avoid it if I can.
The design itself is relatively flat, compared to most other Yagi-based antennas, which means it will be less prone to collecting ice and snow and less likely to act like a sail in high winds. I can mount it directly to the side of each structure that needs connectivity, like a porch light, while aiming at the next closest node to create the wireless mesh.
I'll probably need to copy the overall shape of the enclosure seen in Andrews' original presentation of the antenna.
The node hardware platform will likely revolve around a small travel router or access point board, with an external antenna and PoE capability.
I have several in mind like the GL-AR150 and similar devices. At present, OpenWRT 18.06 seems to be supported on that device. I want to make sure whichever device I settle on as a base for this will be at least be secure for the foreseeable future, if not feature rich. If I use two antennas, I can dedicate one to transmit and the other to receive, creating a true duplex link.
There's an old truism in marine research: "Don't put anything in the ocean you don't plan to lose". Or something to that effect. The harsh environment of the ocean and its vast depths being the biggest enemies. There's a much less intense parallel on land; Anything exposed to the Sun and the elements will eventually degrade and malfunction.
The enclosures that come with most access points are no match for the elements, which means I would either have to make a DIY case for it with an outlet for the ethernet cable or buy a NEMA-rated enclosure and modify it to my needs. I'd rather not have a large, ugly, portruding "thing" outside my structures, even in the name of better connectivity, so some customization will be necessary anyway. The devices themselves will need to be tested independently to ensure they can survive the temperature swings. I can at least control the humidity by using adequate seals on the cases.
The cases are probably going to be the most complicated parts. UV resistant resins are available in the market, usually labled "marine grade", but I have no experience casting shapes from these.
Another useful skill to learn.
All in all, it's been fun exploring what options are available to me should I pursue this path to connectivity.