signal variations

Discussion in 'General Discussion' started by yensch, Dec 9, 2005.

  1. yensch

    yensch Network Guru Member

    hello @ll,

    i have some problems with WRT 54 G there is a oproblem with signal variations all router (8) have the same problem the first 2 min the signal is ok but than i have variations for 50 sec. after this time the router comes back to a normal signal and down after the next 1 min.

    any idea what can i do ??


  2. Esquire

    Esquire Mesquire Staff Member Member

    Have you tried changing your wireless channel to see if you are being affected by interference?
  3. simax

    simax Network Guru Member

    Yes, that seems a lot like a dense channel area.

    REMEMBER, there are actually only THREE "real" (isolated from each other) channels: 1, 6 and 11.
    Do a site survey and try to get as far as you can from the local channel usage.

    And let us know.
  4. Esquire

    Esquire Mesquire Staff Member Member

    All channels on a router are "real" channels. The claim that only 3 of them are real is based on a misapplication of frequency spectrums.

    While channels 1, 6, 11 are said to be non-overlapping with each other because their frequency spectrums do not overlap, these spectrums do overlap with that of the channels next to them, i.e., channel 1 will overlap with channel 2, 3, 4, etc., and channel 6 with 4, 5, 7, 8, 9, so on and so forth. Thus the real benefit of non-overlapping channels is exaggerated, especially in an environment in which all router channels are being occupied. This is made worse by the fact most manufacturers default their channels to either 1, 6, or 11, hence increasing the potential of causing more interference to neighbouring networks.

    In fact, the same "misunderstanding" can be applied to other channel sets, such as channels 2, 7, 12 since the channels within each set do not overlap with each other, so if one wants to use a different channel, try all channels available to the router - 1, 6, 11 may not be good enough.
  5. simax

    simax Network Guru Member

    Certainly. You just took the time to explain it fully. However, there's no doubt that, say, if the local survey gives you a lot of usage of lower channels few on the 6-9 (for instance), the best choice is 11.

    I usually don't comment on >11 since those are not allowed in all markets.
  6. Esquire

    Esquire Mesquire Staff Member Member

    Right, but if and only if there isn't any other network on channel 11. If the next strongest signal after your own is (say) another Linksys broadcasting at its default channel 11, placing your own at 11 will create the worst possible interference with each other.

    Don't forget there are also household 2.4GHz cordless phones, microwave ovens, and other radio devices to contend with, which can be broadcasting on the same frequencies and they go undetected if they do not use a Wi-Fi radio chipset (my two 2.4GHz phones are case in point - only the one using a Atheros chip is detectable). Having said that, a good cordless phone will jump to the next best frequency if there is intereference in order to maintain signal quality, which can either be good or bad to a wireless network, depending on situation.

    A local survey can also provide the strength of the surrounding signals and of their consistences. Armed with such information, one can possiblt place the network in a channel least occupied and with the max separation from other channels in use, which may not may not be channel 1, 6, or 11, provided there isn't any undetectable household phone present on the same frequency (the effect of which will not be known until the network is in use).
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