WiFi Antenna Location Sensitivity

Discussion in 'Computer Support' started by Jeff Wisnia, Mar 14, 2009.

  1. Jeff Wisnia

    Jeff Wisnia Guest

    I'd like to learn why sometimes moving a wireless adaptor's antenna by
    just a few inches can cause a significant performance difference.

    Ex: Today SWMBO came down to my office (We both work in our own
    business' office.) complaining that internet access on the computer in
    her office was slower than molasses in January.

    We use a Linksys WAP54G router to service the five computers in our
    business. Her computer has a Linksys WUSB54G adaptor plugged into it.

    I gave her my usual reply that MY computer was connecting just fine and
    that she has so much junk and obsolete files stuffed in her computer
    that it probably needs an enema to get its performance back to where it
    used to be.

    That strateguy didn't work, so I hauled my ass down to her office and
    had a look.

    She was correct, internet access on her computer was awfully slow, even
    though none of the other computers in the office were in use then.

    Her computer is the closest one to the router, only about 25 feet away
    with nothing more than a couple of drywall partitions in the way. The
    adaptor software reported excellent signal strength and I checked to
    make sure that the wireless channel we were using was still unoccupied
    by any of our neighbor's wireless systems.

    To make a long story shorter and less boring, I solved problem by simply
    moving the wireless adaptor about four inches sideways on the bookshelf
    it sat on, and her computer instantly regained its usual internet access

    I understand how multipath signals can cause RF nulling, but I'd expect
    that the adaptor's software would report "poor signal strength" under
    those conditions. It's the "good signal" report combined with lousy
    performance that has my inquiring mind wondering what's really going on.

    Thanks guys,

    Jeff Wisnia, Mar 14, 2009
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  2. Jeff Wisnia

    Mike Easter Guest

    Because it is a radio transmitter-receiver and "all kinds of crazy things"
    can affect the quality of the signal getting around. Including
    .... and other stuff. Gee, /only/ 25 feet of walls and all of the things
    that are next to and inside walls and in between walls on the floorspace.
    Imagine trying to shine some kind of light-like beam which can penetrate
    some things better than others from some kind of undescribed 'adapter'
    back and forth to some kind of router antenna.
    Sometimes that information is worthless.
    3 quick adages. I would rather be wired than wireless. I would rather be
    able to see (with my eyeballs) one antenna from the other than not. And
    you can't trust 'excellent' signal strength to mean excellent clear
    Mike Easter, Mar 14, 2009
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  3. Jeff Wisnia

    Helpful guy Guest

    See Mike Easter's reply.

    Moving a flashlight a few inches can cause it to completely miss the window
    25 meters away.
    RF (Radio Frequency) is not very different. If you could see it like you can
    see light you would immediately see the answer to your question.

    If you want a reliable network use wires.
    Helpful guy, Mar 15, 2009
  4. Jeff Wisnia

    Helpful guy Guest

    Same with 25 feet :)
    Helpful guy, Mar 15, 2009
  5. Jeff Wisnia

    chuckcar Guest

    Wrong. We're talking microwaves here. That's line of sight. That's *why*
    weather radar (and plain radar) works.
    chuckcar, Mar 15, 2009
  6. Jeff Wisnia

    Helpful guy Guest

    Don't worry I know what an omnidirectional antenna is.
    I think you should go back to wireless networking school.
    When did you last see a laptop user carrying a Yagi around with it?
    The Yagi antenna is a Japanese invention but not relevant to this thread.
    Helpful guy, Mar 15, 2009
  7. Jeff Wisnia

    Helpful guy Guest

    Ok and how is this relevant to what the OP asked??
    Do you suggest he gets a Yagi for all of his users?
    Or would 25 feet of wire and a few holes in the drywall be a more economic
    and reliable option?
    Helpful guy, Mar 15, 2009
  8. Jeff Wisnia

    PeeCee Guest


    What Philo says is right, multipath can cause distortion as well as nulling.
    Think of a TV picture with ghosting in it, the signals are strong but arrive
    at differnent times and distort the picture.
    In the case of WiFi the data bits are what get distorted so the routers
    spend all their time resending packets because the checksums don't add up.

    Mike's advice is also worth noting:
    Use wire if you can.
    Wireless works best when you can eyball antenna to antenna.

    It's also worth noting that WiFi is slow compared to Wired networking.
    Even the new 'N' standard is slow compard to the Gbit Wired NIC's most PC's
    come with today.

    PeeCee, Mar 15, 2009
  9. Jeff Wisnia

    Evan Platt Guest

    A CB license? Wow.

    Must have been tough. I'm sure the toughest part was making out the
    check to the FCC.

    What license do you have now?
    Evan Platt, Mar 15, 2009
  10. Jeff Wisnia

    Jeff Wisnia Guest

    That's the answer I was seeking, the TV ghosting analogy was appreciated.


    Jeff Wisnia, Mar 15, 2009
  11. Jeff Wisnia

    Evan Platt Guest

    Do you mean Ethernet?
    No you don't.
    Why not?
    Splitters??? What are you talking about?

    You really have no clue do you?
    Evan Platt, Mar 15, 2009
  12. Jeff Wisnia

    Whiskers Guest


    'Something' was in the way of the direct path between the two aerials;
    could have been an ornament, or a water pipe, or a length of cable, or a
    steel joist, or a drawer full of cutlery. WiFi signals are easily
    reflected or blocked. You can turn a normal omni-directional WiFi aerial
    into a directional one with a bit of aluminium foil, and a baked-bean tin
    (with or without the beans) would be enough to create a 'blind spot'.

    That a small movement of one of the aerials improved performance, suggests
    that the obstruction was close to that aerial.
    Whiskers, Mar 15, 2009
  13. Those are for the coaxial cable. You can't plug a coax directly into a
    The coax feeds TVs, or more often, a digital TV box. The normal
    definition of a "cable modem" has nothing to do with TVs.

    One feed from that splitter can/may feed the actual cable modem, whence
    you would plug in your router (multiple PCs) and then via Ethernet cable
    to the computers. If you have multiple "cable modems" you need multiple
    IP addresses.

    I have a one-to-four splitter. One goes to a digital TV box for a LCD
    digital hi-def TV, one goes to an old analog TV, and one goes to my
    cable modem, where there is Ethernet to router, thence to three
    computers via Ethernet cables. The fourth is unused.
    Absurd question.
    Not true, based on your post. You have no clue about cable internet...
    Beauregard T. Shagnasty, Mar 15, 2009
  14. Beauregard T. Shagnasty, Mar 15, 2009
  15. Jeff Wisnia

    Evan Platt Guest

    Hmm. Funny, I can't get my etherenet cable to plug into that.
    With a splitter.
    No, you don't because you mentioned a splitter for HOME NETWORKING.

    You going to use RG58 for home networking, stoopid?
    Evan Platt, Mar 15, 2009
  16. Jeff Wisnia

    Evan Platt Guest

    Evan Platt, Mar 15, 2009
  17. Beauregard T. Shagnasty, Mar 15, 2009
  18. Jeff Wisnia

    G. Morgan Guest

    That is not the optimal setup. You should have the main drop split with a
    2-way, one to the modem and one to another 2-way splitter with both TV's
    connected to it.

    If you need an explanation why, I can provide one if necessary.

    "Newspaper claims car thief transformed into a goat"

    **Important Update**
    Magic goat detained for armed robbery:
    G. Morgan, Mar 15, 2009
  19. Jeff Wisnia

    G. Morgan Guest

    G. Morgan, Mar 15, 2009
  20. Jeff Wisnia

    G. Morgan Guest

    G. Morgan, Mar 15, 2009
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