Burying ethernet cable (or wireless??)
October 19, 2021 6:45 AM   Subscribe

I think I need to bury about 80m of ethernet cable, in order to extend Internet access from an old house to an even-older barn. We have a tractor and willing hands. What else do we need, and how do we do it?

A pair of wireless repeaters would be easy, but possibly ugly; it is an old site, after all. We have line of sight, though, so I am willing to be persuaded by anyone with good experience here. At the same time, we're well within the 100m limit of ethernet, as long as we don't have any big detours.

This is in New England, so it gets cold. Do we have to go below the frost line?

What kind of cable -- Cat7?

And last, what kind of conduit do we use? A roll of something (similar to PEX), or rigid segments that get stuck together?

I do know that we should bury warning tape on top of any conduit or line (a few inches shallower), and also that we should run a second, idle line Just In Case. The organization is all-volunteer, and would prefer to do it ourselves instead of paying a cabling contractor.
posted by wenestvedt to Computers & Internet (24 answers total) 4 users marked this as a favorite
First, you may require electrical permits/inspection, depending on your jurisdiction. Second, you should perform a site survey to check for any buried utilities (they can be in surprising places); power/gas companies will usually do this for free.

You can buy ethernet cable, in bulk, that's rated for "direct burial" (that is, no conduit necessary). Direct burial is often better than conduit because water can get into conduit and do bad things, but a direct burial cable is basically impervious. If you have moles and the like, then go for metal conduit and resign yourself to water getting in there somehow (so beware where the conduit terminates lest it pour water into your house, and use a direct-burial cable in the conduit anyway). Leave a pull string in the conduit just in case.

Regarding depth, if you DO need an inspector, it is very possible that they will interpret NEC Article 820 as something that applies to direct burial ethernet (I do not believe it does, but you are unlikely to win an argument with an inspector) -- so in that case, bury at least 12" down lest the inspector object.

Use "lazy" corners (big radii) for any turns. Bury below the frost line, especially if you're using conduit (lest the heaving break the conduit). Consider putting pea gravel in the bottom of your trench to help with drainage.
posted by aramaic at 7:02 AM on October 19 [6 favorites]

Does the barn's power come from a different transformer than the house? You will have lots of electrical gremlins because of the difference in ground potential if that is the case.
posted by JoeZydeco at 7:05 AM on October 19 [5 favorites]

JoeyZydeco raises a very good point: ground loops are bastards. Some tips.
posted by aramaic at 7:09 AM on October 19 [2 favorites]

The other relevant thing with ground loops (as aramaic's latest link identifies) is that you have to be careful about shielded vs. unshielded cable. The shield in a shielded cable should be grounded (on one side only of the installation), and to avoid a ground loop you want to make sure you run *un*shielded cable between the shielded jack and the powered electrical equipment on one side of the run. You should never have shielded cable just hanging out by itself without the shield going to ground.

Another way to avoid dealing with ground loops is to run PoE and just not connect any equipment to mains power on the barn side. Still have to run shielded cable though.
posted by goingonit at 7:13 AM on October 19 [1 favorite]

You may be able to get away with just a single high gain directional WiFi antenna on the house pointed at the barn. You might be able to mount the antenna inside the house's attic (depending on how thick the wall/roof is) so it's not visible.
posted by soylent00FF00 at 7:14 AM on October 19 [1 favorite]

I'd recommend just going wireless if ground loops become a possible issue.
posted by JoeZydeco at 7:15 AM on October 19 [1 favorite]

Ars Technica recently did a review of long range wireless bridging that seems like a whole lot less of a pain in the butt than trenching ethernet, but it depends on your requirements - if you want to get gig out in the barn so you can move your homelab out of the house, wireless probably isn't the best option, right? But if it's just "eh, connectivity to the home wifi kind of sucks, but doesn't suck enough to kick my phone over to cellular", that might be a solid answer.
posted by Kyol at 7:29 AM on October 19 [4 favorites]

I'd run fiber. It will save you a huge amount of worry about electrical issues, and while it's a bit more expensive, you can get a 100M pre-made direct burial fiber cable off Amazon for a couple hundred bucks, and you can find cheap ish switches with sfp ports and DACs to connect between the fiber and the switch (that might need eBay, or maybe not).
posted by wotsac at 7:49 AM on October 19 [11 favorites]

We ran cables rated for underground use for both internet and TV about 75 feet and protected it using PVC pipe. We dug below the frost line (northern Wisconsin) and have had no problems at all. It's been 18 years.
posted by carmicha at 7:52 AM on October 19 [2 favorites]

If I was doing this (and have actually done so at a previous house) I would lay fiber optic, in conduit. That would get rid of ground loops but also protect against induction by lightning strikes, even when those wouldn't hit the house, barn or the route of the trench directly. Converters to go from wired ethernet to fiber aren't that expensive nowadays (you of course need one at each end); the fiber itself will be about the same price as direct burial cable but you'd have to add the price for the conduit.
posted by Stoneshop at 8:12 AM on October 19 [6 favorites]

I would consider using two of these Ubiquiti Nano Station 900 MHz units. I successfully used them to beam an Internet connection from my house to a business I owned that was just over 100 meters away (and the wireless signal had to pass through a residential property located between the two buildings). Yes, I lost some bandwidth, but I was able to obtain a fairly stable, usable connection on the far end (with bandwidth around 10-20 megabits per second). The Ubiquiti units are not ugly and can be mounted outside -- though in my case, they were both indoors, near windows. Note that if you get these units, the included instructions are completely useless, but some kind soul left a detailed comment on the Amazon page with directions on how to configure the devices. If you have unobstructed line-of-site, you'll probably get great results. It's a lot less effort and expense than burying a cable.
posted by alex1965 at 8:20 AM on October 19 [2 favorites]

You don't have to use conduit: direct burial ethernet cable should work, but it's still vulnerable to the random shovel digging in the area. One trick is to put some gravel or sand on top of the cable in the trench in the hopes that anyone digging in the future will say "hmm that's strange" and not break your cable.

I just buried some irrigation wire (similar to ethernet) and elected to put it in 1/2" PVC pipe conduit. I'm guessing 80m would be about $150 to protect your cable. Thread a string through the conduit too so you can pull extra cable in the future if you need it. We didn't bother gluing or sealing the PVC joints, just pressure fitted them.

Be aware there's a 100m limit on ethernet length. You can cheat this in most circumstances, and you're under that anyway.

Wireless absolutely could work; I used a pair of Ubiquiti Nanos for this purpose a few years ago, see this AskMe for details. The Ubiquiti setup is kinda complicated and a purpose-built solution like Mikrotik Wireless Wire may be easier. Or as soylent00FF00 says, a single good WiFi antenna at the barn might be sufficient. I'm not up to date on recent products in this area but I'd expect it to be a couple hundred bucks. Any wireless device will be conspicuously computer equipment, but relatively small.
posted by Nelson at 8:24 AM on October 19 [1 favorite]

Also, if you are going to use conduit, the choice between a single length of PEX or a number of lengths depends on how many lengths you would have to use (iow the number of joins and especially how smooth they would be on the inside) and whether there will be any bends in the trench. Bends, or when you can only get conduit that doesn't couple with smooth joins on the inside: use PEX.

I don't see anything but PEX or a similar type of continuous tubing for buried fiber here.
posted by Stoneshop at 8:30 AM on October 19 [1 favorite]

I recommend a couple direct-burial single-mode fiber pairs. An SFP transceiver on each end is pretty cheap compared to the hassle of long wire runs between two buildings. Fiber rather than STP will about double your run cost. If you go through a fire-rated wall at an ingress point, use approved methods and materials to maintain that rating.

*If* you're absolutely stuck with Ethernet over twisted pair: Cat 7 S/FTP, direct burial; two cables in the trench; warning tape not strictly needed (the shielded cable will show up quite well) but can't hurt if you can afford a roll. The above advice to only ground one end is ... tricky. Grounding one end solves your ground loop problem and *probably* makes your lightning strike induced voltage performance better, but can make it *worse* in some circumstances. (It's difficult to model because, for short runs like yours, you have to model the near field effects and the ground potential rise.) Ethernet is well-isolated at 1.5 kV but nearby strikes can readily induce many times that. Consider lightning protection equipment for the line. Yay.

Again: fiber is so much simpler for slightly more cost.
posted by introp at 9:17 AM on October 19 [5 favorites]

Having done both, for me the decision between wireless and running a cable (I do agree that fiber is preferable, but not strictly required here) comes down to your priorities and tradeoffs.

Pros of wireless:
  • Less labor to install.
  • Lower equipment and material costs.
  • Possibly easier to service/upgrade down the road.
  • If you try it and it doesn't work well, you can still trench and run a cable, and you're only out a small amount of money and effort.
Pros of running a cable/fiber:
  • The resulting network connection will be faster.
  • It will be more reliable.
  • It will probably be more aesthetically pleasing (no visible wireless hardware needed.
So, really, do you care more about fast to install and cheap, or about high performance and reliable? That will make your decision for you.
posted by primethyme at 9:43 AM on October 19 [1 favorite]

If you have clear line of sight, you can get a pair of 60GHz wireless bridges for a couple hundred bucks that will have no problem doing 1Gbps.

If you prefer to bury cable, do fiber and put a media converter on each end. fs.com has everything you need. If you are going to put in switches with SFP or SFP+ ports on either end anyway, fs.com optics are under $20 each, but media converters are less likely to require fiddling.

Long copper runs are a good way to get equipment blown up by lightning. By the time you install a protection system that will do anything but make you think you aren't going to get bitten you'll have spent more than the cost of the preterminated fiber.
posted by wierdo at 10:56 AM on October 19 [1 favorite]

Get a set of ubiquity nano bridges that is going to be your best option. Alternatively get a length of pre terminated direct bury fiber with media converters at both ends. Don't run copper network between buildings.
posted by jmsta at 10:58 AM on October 19 [1 favorite]

You will have lots of electrical gremlins because of the difference in ground potential if that is the case.

I don't think this is true with Ethernet, at least not with the unshielded twisted pair that is commonly used in the US. (I think it's a problem if you are using Euro-style shielded twisted pair, and don't do the thing where you intentionally lift the shield at one end of the cable).

I'm not totally hip on how the latest generation of twisted-pair Ethernet PHYs work, but old ones used to have actual transformers for each "loop" (where a loop is a pair of wires, e.g. "white-green" / "green" or "white-orange" / "orange"), in order to change the push-pull balanced differential signaling on the line into a single-ended voltage for the PHY chip. It may be that modern units use some sort of solid-state tech like optoisolators or something, rather than literal magnetic transformers, but I find it very hard to believe that this functionality has been eliminated completely, since it's a core part of how twisted-pair cables manage to transmit the bandwidth that they do over relatively long lengths and reject interference. This article from 2016 says quite clearly that "magnetics are not optional", which tends to make me more confident this is still the case.

Anyway... if I was going to go to all the effort of digging a trench, laying cable, etc., I'd sure as hell bury several of them. And probably a piece of fiber as well, just for future-proofing. Even if you don't use the fiber right away, eventually Ethernet is going to hit the theoretical max for twisted-pair and you might want it.
posted by Kadin2048 at 11:32 AM on October 19 [2 favorites]

but old ones used to have actual transformers for each "loop" (where a loop is a pair of wires, e.g. "white-green" / "green" or "white-orange" / "orange"), in order to change the push-pull balanced differential signaling on the line into a single-ended voltage for the PHY chip.

New ones still do as they are part of what's necessary to run PoE. You don't want those 48 volts (or even the lower voltages fake 'PoE' uses) to come anywhere near your ethernet chippery, and those transformers can do double duty separating the DC voltage between pairs from the signal as well as dealing with balanced signalling and correct termination.
posted by Stoneshop at 12:15 PM on October 19

I live in Canada (where it also gets below freezing) and have a plain old ethernet cable running into my house from a modem that's attached to a utility pole about 60m away that itself has an ethernet cable running from my neighbor's house that's even farther away. So, other than the daisy chain, it's a similar case to what you want to do. We have the cable inside a flexible black plastic tube about 1" in diameter. Im not sure what it's called, but the walls are probably 1/8" thick and it's not super bendy. It's buried in some places where the yard occasionally gets driven on, or where it runs along a walkway, but there are definitely places where it's just above ground or only an inch or so below it. We havent had problems with temperature as far as I can tell.

That said, our internet maxes at about 5mb which although enough to stream and do video calls is certainly not the kind of speed you might have/want and I'm not sure if higher speeds are affected by temps.

We just dug the ditch where it was needed with pickaxes and shovels.
posted by ananci at 1:11 PM on October 19 [1 favorite]

Be aware there's a 100m limit on ethernet length.

That's for wired ethernet; fiber is good for at least 500m even with the least expensive cable and converters, so if for some reason you have to make a detour (tree roots, rocks, an underground secret survival bunker) you won't be stuck for distance. Keep in mind that for consumer-grade networking like this there are two kinds of fiber: multimode and single mode, and the optical side of your converters (most often an SFP) has to match that. The connectors on the cable obviously has to fit the converter as well; if you have SFP 'optics' the fiber should have LC connectors.
posted by Stoneshop at 1:56 PM on October 19 [1 favorite]

The 100m limit is not actually true (mostly) anymore. It derives from the Carrier-sense multiple access - Wikipedia era. Back on thick and then thin cable days computers were daisy-chained in a line. The limit of length is a calculation based on the shortest possible packet getting from one end to the other and back. A machine on one end must be able to send a packet and if coincidentally the machine on the other end sends a packet at the same time the packets must overlap to create the jam/collision signal. If the cable is longer.... it's possible for a machine on one end to send a packet and not know that there was a collision. With switches and twisted-pair it's not the same as there are only the two machines on the same link instead of many. You can go a good bit further than 100m (if needed).

I would also lay some sort of conduit, install a 170m pull string (make sure to physically attach each end on each side so that you can't accidentally pull your pull string through. Then it's fiber and a couple of media converters. You're going to a barn, you don't need some fancy router with a SFP and a ton of ports or such, just a little box with a wall-wart on each side that does the fiber to ethernet conversion, then you can use a cheap switch or even just plug in an access point.

I didn't know that there were just toss in a hole in the ground ethernet cables. Wow. My big university network engineer sort of mind just goes "hell no" at just burying a cable in the ground. That's just not how we do stuff.

Two fiber-ethernet converters on either side, a buried (whatever works for you) pipe with a pull string inside and then pull some fiber through... no fuss, no muss, no worries. I'd support that.
posted by zengargoyle at 6:03 PM on October 19 [4 favorites]

The 100m limit is not actually true (mostly) anymore. It derives from the Carrier-sense multiple access era.

Not wanting to derail too much, but cable lengths for twisted pair ethernet are limited by signal degradation, not CSMA/CD considerations[0]. Because those signal level limits are based on worst-case conditions, and as signal processing in the network equipment tends to be able to still deal with signals that have dropped a bit below the minimum level specified in the standard you can usually exceed that maximum length by 20..30% without the link falling over. On top of that, the network gear on both ends will try to negotiate a speed at which they can maintain a stable link, and if that's 100Mbit/s due to the cabling they will just do that even if they're both capable of 1Gbit/s. So you'll see a stable link, just not at the speed you're expecting.

[0] CSMA/CD only applies to 10Mbit/s networks with multiple devices strung together using coax cabling, and their maximum lengths are actually 500m for 10b5 (thickwire) and 185m for 10b2 (thinwire).
posted by Stoneshop at 1:42 AM on October 20 [1 favorite]

Could plc be an option ?
posted by nicolin at 11:41 AM on October 20

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