Monthly Archives: November 2013

The hard part of wireless networking: the wires.

It’s actually an old joke in the wireless networking world: what’s the worst part of wireless networking? The wires!

(OK, it’s an old dumb joke…)

While having WiFi all over the farm is incredibly useful, the only way to make it happen is using Ethernet cables. While Ethernet cables are very simple devices, there are an amazing number of variations and types of Ethernet cables, an choosing the wrong ones (or using them poorly) can cost you time and money.

What is an Ethernet cable?

Courtesy of WikiMedia

Ethernet cables all have some common characteristics: they contain 4 pairs of wires, with each pair twisted around each other (so they are called “twisted-pair” cables). They have an outer sheath to protect the wires inside and they use RJ-45 connectors to connect to networking devices.

The 4 pairs of wires inside the sheath are usually colored green, brown, blue, and orange – one solid and one striped for each color. The wires are usually 100{8fd1ffa65f67a2e931916b3c1288d51eed07dc30586a565c92d055673de7c64e} copper, but some cheaper cables are made of alloys. Alloy cable works OK for short lengths, but should not be used for cables longer than 25 feet. There is sometimes an uninsulated wire running down the middle of the cable called a “drain wire” – this is meant to provide a common ground for the equipment the cable is connected to.

The wires are usually about 24 gauge (AWG), but some cheaper cables use 26 gauge wire, and some more expensive cables use 22 gauge wire. Obviously, the bigger the wire the better, as long as it’s pure copper, but bigger wire also makes heavier cables. It makes a difference if you’re hauling it up a ladder, believe me.

Kinds of Ethernet Cables

Under the sheath, some cables have a shield made of metallic braid or foil. This shield keeps outside noise from penetrating the cable and disrupting the signal on the wires. Unshielded cables are designated as “UTP” (Unshielded Twisted Pair), while shielded cables are designated “STP” (Shielded Twisted Pair). Our experience shows that any cable over 25 feet should be shielded to prevent corruption of the data on the wires and maintain the speed of the data.

You will see, shopping for Ethernet cables, that there are several “Categories” of cable – Cat 5, Cat 5e, and Cat 6 are the common ones available now. The differences are in the speed rating of the cables – Cat 5 can pass data at 10 Mbps or 100 Mbps, Cat 5e can pass data at 10, 100, or 1000 Mbps, and Cat 6 can go up to 10 Gbps. Any of these will work well with AyrMesh equipment – we usually buy Cat5e cables because they are less expensive and widely available. The main physical differences in the cables is how tightly the wire pairs are twisted together.

Finally, the sheath itself can differ quite widely. The normal sheath is usually a form of polyolefin, which does not burn easily. “Plenum-rated” and “Riser-rated” sheaths are coated with a low-smoke PVC, which makes them even more flameproof and reduces the toxicity of the smoke if they do catch on fire. “Direct burial” cables generally have a very thick and heavy sheath, and they may contain a gel that prevents a nick or cut in the cable from admitting water into the cable. Obviously, if water gets into the cable, the wires can corrode and the cable will go bad, but direct burial cables are usually very stiff and very heavy, making them extremely difficult to work with.

Whichever cable you choose, it is imperative that you handle it correctly. Because the cable consists of a bunch of small wires, it is really no stronger than any of those wires. It’s very easy to get a kink in a cable when you’re pulling it through a hole, for instance, and break one of the wires. When that happens, the cable is generally useless.

General Guidelines for Ethernet cables used with AyrMesh products

  • Make sure the cables are all-copper and shielded (STP) if they’re 25 feet or longer.
  • Try to get 24 or 22 AWG wires in the cable.
  • Get plenum-rated or riser-rated cables for use indoors, but don’t use direct burial cables unless you’re going to bury them – they’re too hard to manage.
  • ALWAYS leave a “drip loop” when you’re bringing a cable run from outside to inside a building so water doesn’t run down the cable and ruin equipment!
  • Be VERY careful pulling cables – they are more fragile than they seem!

Using the Internet on the Farm

It seems almost impossible now, but it wasn’t very many years ago that the typical farmer would have laughed if you said that he’ll need Internet access everywhere on the farm. The benefit of surfing websites (when they were just static information pages with pictures) was unclear, but the idea of carrying around a computer in your truck, tractor, sprayer, or combine was patently absurd. The dust, temperatures, and vibration were far too much for the computers of the time.

But then came the Blackberry, and everyone discovered the convenience of getting email on-the-go. So everyone realized they needed a Blackberry and constant access to email – why would you need anything else?

But the web grew up. More and more information was either available exclusively on the web, or was at least a lot more convenient to get on the web. Furthermore, it became about more than just getting information: you could increasingly actually DO things on the web – ordering parts and supplies, keeping records, planning, and even marketing. But laptops have never been practical on the farm: keyboards are too easily gummed up with dust, screens on hinges are too fragile, and they just take up too much space.

Then another device came along: the iPad. I have joked that EVERY farmer in America got an iPad for Christmas last year, and tablet computers like the iPad seem like they were made for farming. Adam Gittins has written an excellent blog post about the use of tablet computers in agriculture – the bottom line, though is that they are durable, easy to carry, and provide an excellent platform for using web applications.

Of course, they need to be connected to the Internet to be useful. Almost all the tablets on the market are available with some sort of cellular modem that allows them to access the Internet, but fast cellular data signals (“4G”) are rare in the rural U.S., and there are a lot of areas with only very slow or no cellular Internet access. Furthermore, a cellular modem does not provide you access to your Local Area Network (LAN) the way the AyrMesh network does. Finally, of course, the cellular options in the tablets cost extra, and the cellular companies like to charge quite a bit per month for Internet access.

Using the AyrMesh system, you can have fast WiFi access all over your farm, with access to your LAN for accessing the data sources and control mechanisms on your farm, and it makes your tablets and smartphones just that much more valuable.