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Wireless Networking Hardware

Propagating a Signal Through Old Walls? 64

Posted by Cliff from the guiding-signals dept.
avjewe asks: "I have a wireless (802.11) network in my 100 year old house. The walls are thick plaster, with enough metal in them to block the signal quite effectively. The floors, however, pass the signal just fine. Does anyone have any experience or suggestions as to how one can propagate a signal through a maze of faraday cages? I recently added an omni-directional antenna which, as one would expect, boosted the signal where I already had one, but didn't help the dead spots."
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Propagating a Signal Through Old Walls? More

Propagating a Signal Through Old Walls?

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  • Sledgehammer? (Score:5, Funny)

    by swillden ( 191260 ) * <shawn-ds@willden.org> on Wednesday August 04, 2004 @06:36PM (#9883856) Journal

    I realize it has some downsides from the aesthetic point of view, but, really, what's more important?

    • Re:Sledgehammer? (Score:5, Funny)

      by HRbnjR ( 12398 ) <chris@hubick.com> on Wednesday August 04, 2004 @07:16PM (#9884247) Homepage
      As a corollary to this, I would suggest the following:

      a) a large drill
      b) a large spool of cat 5 cable
      c) a crimping tool
      d) electrical tape*

      * One might incorrectly assume the electrical tape is just for use with the cat 5 cable, when in fact it's primary use is for tying up your wife to keep her from hurting you while you drill cable holes through the living room wall :)
      • One might incorrectly assume the electrical tape is just for use with the cat 5 cable, when in fact it's primary use is for tying up your wife to keep her from hurting you while you drill cable holes through the living room wall :)
        Make sure to save a little bit for some "fun" with the wife afterwards :P
      • You need a home powerline network [macwireless.com]!

        The MacWireless Powerline Network Adapter allows you to route your network through the electrical lines in your home or office. With speeds up to 10 times faster than DSL, this is a great way to get your ethernet network to other floors or rooms in your building, without the need to run wires. Powerline Network Adapters are particularly useful when concrete, metal, or other obstructions in the walls of your home or office block your wireless signals.

        • Current wiring standards use either 4 or 8 wires in a twisted pair setup. Power lines provide only three wires and there is no guarantee you will find a nicely twisted pair there.

          Tim

          • Re:Sir (Score:3, Interesting)

            by Jeremiah Cornelius ( 137 )
            Yeah - but we arene't sending 10+ MBPS 802.3 signal, either.

            Powerline networking is using live, unshielded, untwisted electric wiring as a collision-tolerant physical medium to trancieve the equivalent of 802.11 datagrams...

            It's "wired" wireless - for the scenario in question.

            (Thinks me, to myself: "Was that a subtle troll?")

      • Most fairly modern houses (built in the last hundred years) have pretty standard construction. Lath and plaster is a bitch to patch up, so make your cable holes small, and if possible in corners where you can hide them with stuff.
      • Might I also suggest a "flex bit." They're $20-30 at the local hardware superstore and since they are 4-5 ft. in length, can also be used to fish the walls. Just be sure that if you are drilling through a fire break that you are perfectly vertical, else you WILL drill through the side of the wall.
      • I convinced my wife (easily) we needed crown molding in the babies room.. (it's between my office and the master bedroom) she readily agreed to add it to the list of renovations for that room, (she was 'nesting' dontcha know)

        then she agreed to the cables run behind the molding...
        3 strands of cat 5, and 5 rca lines... wheee!

    • I guess that's a workable solution -- as long as you don't obsess over silly little issues like "Does that beam help hold up the roof?"

  • multiple antennas (Score:4, Insightful)

    by TheSHAD0W ( 258774 ) on Wednesday August 04, 2004 @06:37PM (#9883864) Homepage
    You might be able to connect multiple transmit and multiple receive antennas to the same access point. I don't know how well it'd work, especially with the receive portion.
    • that would whack the impedance of the output line. Even if you retuned the line with some passive component you'd end up with nasty losses, reflections on the bifurcations and phase interference between the antennas; this kind of stuff is only worthwhile if you're making a phased array (now that'd be fun: make an access point that tracks your position and target enough power to your receiver. but you're still linited by your laptop antenna range & power).
      • Remember that each of the antennas will effectively be isolated from the others due to the "shielding" provided by the walls. You're right about the impedance, though; I suppose an amp/impedance converter would be useful.

        Since you seem to know a lot, what about the receive side? What complications are there in typing multiple input antennas together onto the same line?
        • Hey, thanks but I really don't know much about uware design. Anyway I suppose on the recieving end you'd have the same problems as separated "captators" are injecting phase delayed versions of the same signal. If the source is up front reaching the antennas at the same distance (in phase) with equal cables the signal will sum (possibly overdriving the LNA because of the doubled antenna gain). If the source is off axis the signals injected by the antennas into the amp will be out of phase possibly canceling.

  • Attic? (Score:4, Insightful)

    by Omega1045 ( 584264 ) on Wednesday August 04, 2004 @06:40PM (#9883886)
    Have you tried putting the WAP in the attic? Perhaps there isn't metal in the ceilings?

    • Re:Attic? (Score:3, Insightful)

      by cybermancer ( 99420 )
      That is a good idea. Maybe putting one in the crawl space too.

      Another posibility would be to drill small holes in the walls (along the baseboards or close the to ceiling maybe) and run a wire through the wall with an antena attached on both sides. Maybe a powered repeater.

      I'd try the attic / crawl space first. Let us know if that works.
    • Nice, and if there's any metal or foil in the roof, it will act as a reflector to beam the signal down through the house.
    • Worked for me. I put the access point in the middle of the atic (roofspace), and now can even access it while I'm baby-sitting for the kids down the street!
  • Anybody have experience with Powerline technology in the home?

    http://www.linksys.com/products/product.asp?grid =3 4&scid=33&prid=416

    I've heard Siemens also has some good gear. Better than Linksys?

    • Re:Instant PowerLine Etherfast 10/100 Bridge (Score:4, Informative)

      by mrscott ( 548097 ) on Wednesday August 04, 2004 @07:42PM (#9884472)
      I happen to have experience with many of the various powerline home networking options. Actually, they're VERY cool, and will probably work even on your old cabling. If you're just trying to get one remote system up and running, you'd need two (one for the computer and one to connect to your router - all via Ethernet) and they're around $70 each or so.

      They're not speed demons at 4-8Mbps in real life, but still faster than broadband and not a bad choice at all.
      • Do you have any particular recommendations, or even ones to definitely avoid?

        Thanks!
        • Really none to avoid that I can think of. I've used the D-Link, Netgear and Linksys units and like them all. Actually, they're all identical under the hood and work well together, too. Scott
          • This knowledge is pure gold for me right now. Thanks!!!
            I'd been quite hesitant to buy until now.
            Would you be able to tell me whether they're able to communicate with units that are plugged in on another circuit breaker?
            I've heard rumors that they sometimes do and sometimes don't. Not sure which scenario is more likely. Your experience, thus far?
            • So far, I've had no trouble at all using the units across circuit breakers. They're designed to work that way, even.

              If you happen to have a circuit breaker that has surge protection at the panel (VERY rare), it won't work. Also, don't plug the unit into a plug strip or surge protector. Surge protectors filter out the frequency range used by the power line equipment, so you really do need to plug it directly into the wall. However, if you're concerned about surges coming over the wiring, don't worry. T
    • I am currently using 3 of the Netgear XE102's with good results, much more reliable than the 802.11b I use with my laptop.
  • I dont know if its possible, but could you actualy use the metal in the walls as an antenna? Just expose a part and attach your AP directly to the metal in the wall?

    • Re:use the walls themselves... (Score:5, Informative)

      by j1m+5n0w ( 749199 ) on Wednesday August 04, 2004 @07:07PM (#9884149) Homepage Journal
      I dont know if its possible, but could you actualy use the metal in the walls as an antenna?

      If the antenna isn't properly matched to the radio you can end up with high SWR (standing wave ratio), which could potentially damage the radio. The energy, instead of being transmitted out the antenna, gets reflected back to the transmitter, which can cause it to overheat. That's my understanding, at least. If someone else knows better, feel free to correct me.

      -jim

      • I happen to be a ham radio operator (so I have to know all about SWR and things...), and I'll say you did a fine job of explaining it... except, at 200mW, high SWR isn't likely to create enough heat to kill it... it may get hot to the touch, but I don't think that any irreversable damage will be done. But, yes, SWR will be a problem with that.
  • You could take two antennas, and connect them with LMR. Put one antenna in an area with signal, and the other in a dead zone. Each antenna will catch some of the signal for the other to radiate. Granted the losses are high, but you can bend radio around a wall.

  • My solution (Score:4, Interesting)

    by teknikl ( 539522 ) on Wednesday August 04, 2004 @07:19PM (#9884270)
    My house is old, real old. We have wires running inside old gas light tubes for conduit and lots of knob and tube to mess with signals. The radiators don't seem to be much trouble, unless you're tx/rx ing right in front of one, course they are by the windows so it's never a problem. And yes, we have the old old plaster - very think stuff. Can't even nail in it. Still I managed to find a central location for my little netgear mr814v2 with a stock antenna to do its thing, after some trying. My perfect spot was at the VERY top (9ft up from 1st floor level - we have high ceilings) of the basement steps - attached to the ceiling. From this location it was: a) in the center of the house (very little signal leakage to outside world) b) in between the first and second floors c) hidden away where I could forget it was there and just use it. My advice is - mount it up a wall in the center of your home. Higher the better. For me... this was enough. I still have dead spots where the oversized central 19th century chimney simply refuses to pass a signal. That just means you have to sit on the OTHER sofa to check your email.

    • Re:My solution (Score:2, Interesting)

      by dchamp ( 89216 )
      My house is a 2 story, 3 bedroom built in 1923, and has plaster over wood lath, not wire mesh... so I don't have quite the farraday cage issue.

      My WAP (a DI-614+) is in the basement - about 5 feet off the ground on a shelf. It works great in the whole house, using just the stock antennas. Oddly, I get better reception on the 2nd floor than I do in the 1st floor living room right above the WAP.

      Even though it's in the basement, I can still pick with netstumbler about 50 yard down the street with the laptop s
      • Yeah my basement has 4 ft wide x 8 ft long x 10 ft high field stone pillars upporting the wooden frame. It was very necessary to get the AP out of the basement.

        Location Location Location

    • Re:My solution (Score:1, Funny)

      by Anonymous Coward
      My house is old, real old.

      "really".

    • Oh yeah? Re:My solution (Score:1, Funny)

      by Anonymous Coward
      Well... I live in a 12th century castle (Ok, ok...not technically a castle, but most Americans would call it a castle) with walls that are four to six feet thick. I tried wireless exactly once for about an hour. Gave up quickly and I just have duct taped Cat5 to the raw stone ceiling now.
      Life is tough in medieval europe.

  • I know it doesn't have the coolness factor of WiFi, and it doesn't help you contribute to the criminal deliquency of your neighbors' little wannabe hacker kids, but you could try regular old CAT5, just tack it down along the edges of the walls somewhere and cover it up with some moulding.
    • Due to Military housing regulations, we couldn't drill through the walls and we have 1 phone jack in the entire house. We ended up buying flat 5e [www.vpi.us] cable for the job. Fits snugly up against the walls and we don't have to worry about the doors pinching the cable. VPI didn't give us any problems and worked with us very closely to ensure it would go out with a non standard shipper to get to Europe.

  • Try this (Score:3, Funny)

    by aminorex ( 141494 ) on Wednesday August 04, 2004 @07:38PM (#9884435) Homepage Journal
    solder one pole of your antenna cable to one end of
    the wire mesh behind the plaster, and solder the
    other pole to the other end of the mesh. Voila,
    what was previously shielding has become your
    antenna.
  • Write in from my little sister: Drill little holes and put picture frames over them

  • Short and simple summary and solutions... (Score:5, Informative)

    by stienman ( 51024 ) <adavis@@@ubasics...com> on Wednesday August 04, 2004 @08:15PM (#9884767) Homepage Journal
    Your problem is that you want to get network access to all parts of your home with a minimum of fuss, ideally wireless.

    The walls prevent a single wireless access point from working throughout your home.

    Your implicit question is: How can I, without investing in more equipment, get wireless throughout the home?

    The answer is: You cannot.

    Solutions:

    1) Place multiple access points throughout the home. Honestly, you can get one for $19 now - why are you so worried about it?

    2) Wire passive repeaters throughout the home. Get two 802.11 antennas, put one on each side of the various offending walls, and connect them with their very short cables through the wall. Not great, causes other small problems, but recent radios and APs can sort those out with some loss in quality and speed.

    3) Use APs with two antennas, and mount an antenna on each side of one wall. Means you don't have to have an AP for each section, one AP can serve two sections.

    4) Use wireless bridges and repeaters - again, one antenna on each side of a wall.

    5) Use an amplifier with your AP. DLink, Linksys, etc - they all have amps. Mount the AP and both antennas in the attic. Spread the antennas out, 20-30 feet apart to get the largest cover area.

    6) Use a powerline to wireless adaptor, and place them all over the place. Should be able to buy these very cheaply online now.

    There are many other solutions, but these are the ones that come to mind readily and should be easily implementable by even the most technophobic individual.

    Hopefully you know how to repair cracks and holes in plaster.

    -Adam

    • Re:Short and simple summary and solutions... (Score:1, Informative)

      by Anonymous Coward
      "Use APs with two antennas, and mount an antenna on each side of one wall. Means you don't have to have an AP for each section, one AP can serve two sections."

      You evidently don't know why an AP has two antennas. Typically one is used for transmitting, the other for receiving. Putting one on either side of the wall is a great solution... if you want half-duplex operation.

      Chuck
      • You evidently don't know why an AP has two antennas.

        I guess I could say the same to you, however it occurred to me that there may in fact be a stupid manufacturer (or a very specialized use) that would make an AP in this way. I would appreciate a factual treatment on this claim of yours, since I want to know about these units and manufacturers - and either learn about the benefits, or stay as far away from them as possible.

        Two antennas are used in a diversity situation. They are typically placed a f
        • Mounting one antenna on each side of the wall will work. It may or may not work as desired. Like you suggested, run the AP in diversity mode. (generally the default) The drawback is that with the signal from one antenna getting blocked you will see the strength of the signal pulse. (I have some that do that because they use the stock rubber ducky for one antenna and an aftermarket for the other. It has worked fine for nearly 2 years)

          Other options would be to run a couple cables and wire in more than one
  • If you place your AP in the right location, maybe the reflections will make there way through the house to construct at the dead spots.

    You could stick passive "repeaters" in the walls. This would consist of an antenna attached to an antenna, so the signal gathered by one would be radiated from the other. This would involve holes though...if you're running holes, might as run LAN cables through them.
  • While I've never messed with wireless it occurs to me that you may be able to put the access point on the roof or the side of the building and put the antennas outside.

  • 100 year old plaster? (Score:3, Interesting)

    by millia ( 35740 ) on Wednesday August 04, 2004 @10:13PM (#9885484) Homepage
    don't worry, you're living on borrowed time. that plaster's about reached the end of its lifespan, and when you have to put up sheetrock, problem solved!

    but seriously...
    i have a similar situation, and i solved it by using my cellar to poke up cat5 and repeaters. (i've got a 65 year old house, but it's plaster *on* sheetrock- best of both worlds) my faraday cage used to drive me nuts- move 6 inches over, lose a signal. i just hid the repeaters behind furniture. *note* - i am a bachelor.

    somebody needs to make a repeater/access point that fits in an electrical outlet wall-box, btw. what with schools wanting wireless everywhere, that would make it easy to do. i digress, however.

    now, if you need to run cable, the trick some people do in old houses- take off the- aw dang it, words fail me. the boards around the periphery of the room, on the wall? take those off, and then raise em up about half an inch- run the cable there, and put quarter round molding in front to hide the gap and wire.

    similarly, you can hide wire behind a picture rail. drilling a hole through plaster is always fin, though, as you know. (i always start a hole with, like, a 1/16th inch bit, then after i've drilled through, go back with the size i really need.)

    if you try any of the verious antenna repeaters, let me know. i'd like to get a signal outside in the backyard...

  • Make use of this... (Score:1, Informative)

    by Anonymous Coward
    http://webphysics.davidson.edu/Applets/Poisson/Far aday.html
  • My house built in 1954, is plaster. I have a 802.11 AP and can get signal 3 houses down on each side of me and to the street behind.

    Where does this metal come from and what is it for?

    Your linksys has 2 antennas. Perhaps you can run one with coax to a new location and end up with a better line-of sight. Like move an antenna to another room, so they have different visibility?

    It's a hack, and I don't know if the router can handle it, but it could work.

    • It's called lath. It's basically wire mesh that the plaster is applied to. It was less labor intensive than installing the wood lath strips you would find in even older homes.

      If your house really has plaster and was built in 1954, it's probably sheetrock with a plaster skimcoat.
  • I have the same problem in my house. For us (we're renting and can't make mods to the house) the simplest answer was to use ethernet to powerline bridges. Plug the brick into the wall, plug your ethernet into it, and all the computers on the network are sharing the powerlines at 14 Mb/s.

    It's not terribly fast, but it's easy and reliable. All the adapters I've seen come with DES encryption built in, and you'll wanna set that.
  • Have you looked into radiating cable (aka leaky coax)? It's useful stuff. [timesmicrowave.com] In effect, it's an antenna distributed along the length of the cable. I've used it to get cellular coverage into a metal-walled room. A little more elegant than APs everywhere...

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