Hardened Ethernet cable goes underground
How to environmentally "harden" a Category 5 UTP cable.
Philip Freidin, Fliptronics, Sunnyvale, CA; Edited by Brad Thompson and Fran Granville -- EDN, February 2, 2006
An application required the extension of Ethernet (IEEE 802.3u-1995) service from a home to a garage, a distance of approximately 300 ft. Wireless communication using IEEE 802.11a/b/g equipment had proved unreliable due to the buildings' construction, which comprises stucco over embedded wire mesh. In effect, the buildings' walls form Faraday cages that attenuate radiated signals. Straight-line aerial deployment of the Ethernet cable between buildings would have required installation of support poles, and simply laying the cable on the surface of the ground would expose the cable to damage from automobiles, hungry pets, and inquisitive children. At first glance, burial of the cable appeared impractical due to the presence of a large concrete surface between the buildings. However, an alternate route through an adjacent garden would avoid tunneling beneath the concrete slab but would expose the cable to environmental hazards, such as spade work and burrowing animals.
This Design Idea describes how to environmentally "harden" a Category 5 UTP (unshielded-twisted-pair) cable conforming to EIA/TIA 568B and ISO/IEC 11801:1995 that's terminated with RJ-45 connectors (ISO 8877). Without adding repeaters, a Category 5 Ethernet cable can extend to 100m, or a little more than 300 ft. In this application, the cable run comprises 100 ft of exposed cable, 100 ft of "garden-grade" protected cable, and 100 ft more of exposed cable. To apply the idea, you have to find a way to protect and handle the exposed 200 ft of cable.
Depending on your installation's requirements, you will need various numbers and lengths of the following parts: a 100-ft-long garden hose whose fittings conform to the ANSI/ASME B1.20.7-1991.75-11.5 NH thread-form standard; a 4-Gbyte SCSI disk drive, which need not be functional; a continuous, 300-ft-long Category 5 Ethernet cable terminated in RJ-45 connectors; a 120-ft-long, nylon twine; a 5-in.-long, electrical-grade, adhesive-backed tape; a 2-in.-steel, socket-head-cap, ¼-20-thread machine screw (ANSI/ASME B1.1-1989); and two bricks.
To construct the design, uncoil and stretch the garden hose as straight as possible, perhaps using a driveway as a work surface. Place a brick on each end of the hose to prevent it from curling. If you use only one length of garden hose, cut off and discard the hose fittings. Using Torx or Philips screwdrivers as appropriate, dismantle the 4-Gbyte SCSI disk drive by removing all of the screws that retain the drive's cover. If the cover resists removal, look for screws beneath labels. Remove the drive's head-positioning magnets, which can exert a strong pull on nearby ferrous objects. Use caution to avoid pinching your fingers between the magnets and the steel surfaces. Discard the remainder of the SCSI drive.
Securely tie the nylon twine to the ¼-20 steel machine screw and insert the screw into one end of the hose. Apply the magnet to the hose's exterior to attract the machine screw. Slide the magnet along the hose to pull the nylon twine through the hose. When the screw reaches the hose's far end, untie the twine and save the screw for future use. To ease manipulation of the Category 5 cable, deploy it from either its original dispenser box or a spool mounted on a suitable axle so that the cable can easily unwind. Securely attach the twine to one end of the Category 5 cable. Walk to the far end of the hose and gently pull the cable through the hose. If you encounter excessive resistance, investigate the cause and remove any cable kinks or feeder-end snags.
When the cable appears at the pulling end, stop for a moment. Go to the other end of the hose and wrap an inch or two of electrical tape around the cable where it's just about to enter the hose. Return to the far end of the hose and continue pulling the cable through the hose. Stop pulling when you see the electrical-tape marker. You now have a 300-ft-long Category 5 cable whose central 100 feet the garden hose protects. If you decide to protect more of the cable, repeat the process by feeding the twine through a second length of hose. Use the hoses' couplings to make a watertight joint between lengths. If you take this approach, make sure that you properly orient the hose segments before you spend too much time threading the twine through the hose.
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Well, I appreciate the comments, both good and not so complementary. To answer a few comments, I had tried the shop vac, but in blower mode at the end I was feeding in the twine in a previous project and had not had good luck. When this little project happened, the magnets were just sitting there already, so the shop vac did not get another thought. I'll remember it for next time. As for the destruction of the disk drive, these days the current price and interface standards that are used in PCs makes a 4GB SCSI drive pretty much worthless. It really is not worth the effort of connecting to a system given IDE and now SATA drives. In my case I had a small pile of drives that I had paid $1200 to $1600 each. This seemed a suitable way to decommission them, given that they had old, proprietory data on them. As for electrical conduit, my intent was to run it through a garden area, that has bugs, leaves, water, etc. A garden hose is designed for this environment. Electrical conduit would probably rust. The article was edited by EDN staff, and while there were some improvements, they also added some embelishments and some of my description did not quite get through the way I intended. For example the title now implies burial of the hose, which was never my intent. It sits on top of the dirt, maybe covered in leaves. Another departure is that in my situation, it is actually 100 ft of cable in one building, 100 ft of garden grade cable between buildings, and 100 ft of cable in the other building. I didn't really need 100 ft in each building, but I have learned that when ever you cut a cable to length, it is too short. So I made it as long as the standard allowed. Obviously the article could have been reduced to "If you need to run an ethernet cable between buildings through a garden area, consider running it through a garden hose".
For those of you who felt that this article was not worth the paper it was printed on, you will be glad to know that having now got my first design idea published, I am inspired to submit some more, and they will be much more technical in nature.
Thanks for the rest of your comments.
Philip Freidin - 2006-5-3 18:30:00 PST -
I must say, I was impressed that one can call out the specification for garden hose threaded coupler. But to over-engineering a problem make me wonder if this is not just another BS gone wild?. Distroying a harmless harddive to make a cable-puller is over-kill. See the other responces about the vaccuum-pullers.
FYI ... Pulling one cable at a time through conduit is a bad pratice. One should pull all the cables necessary at the same time; even adding in 'spare' cable(s) to cover future damage is a wise pratice.
Hugh Weinrich - 2006-16-2 11:07:00 PST -
A much easier way to get the string thru the hose is to use a wad of cotton or foam and a vaccum with a hose attachment. tie the string to the cotton or foam, insert the cotton or foam in one end or the hose(it should be just large enough to fit without having to be forced in). tie off the other end of the sting so you cant pull it out from the other end of the hose. use the vaccume at the other end of the hose to suck the string thru.
Steven Cohen - 2006-10-2 05:48:00 PST -
Dear me, is EDN becoming a hobbyist magazine? Or are they desperate for something to publish? And yet they turn down useful design ideas....as it happened to me a few months ago. There must be something wrong in the article selection guidelines...or somebody thinks that this kind of articles attracts more readers.
Mario Pazzini - 2006-2-2 23:58:00 PST -
The garden hose idea is pretty neat but there's a lot simpler way to pull a string through a tube or conduit (metalic or plastic) than by using a magnet and screw. Use your shop-vac or other vacuum cleaner to suck the twine or string through - works great.
Steven Haynie - 2006-2-2 13:43:00 PST
