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Thread: Does cable length affect signal quality?

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    Default Does cable length affect signal quality?

    OK, so i have an Edimax 7318USG USB adapter for use with BT3. The good thing about this adapter is that it has an external aerial socket.

    I bought a length of "extension cable" that would allow me to put an aerial further away than I would normally get with a plain old aerial.

    I would love for someone with some knowledge of aerials to tell me *why* when i hook my extension cable and aerial up to my card, the signal is WORSE? than without.

    Without the external aerial I can see MORE APs than when i plug the extendor in, and put the aerial outside my window.

    Does the LENGTH of cable matter? or is it just a duff aerial.

    Thanks

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    Senior Member streaker69's Avatar
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    Quote Originally Posted by mcai8rw2 View Post
    OK, so i have an Edimax 7318USG USB adapter for use with BT3. The good thing about this adapter is that it has an external aerial socket.

    I bought a length of "extension cable" that would allow me to put an aerial further away than I would normally get with a plain old aerial.

    I would love for someone with some knowledge of aerials to tell me *why* when i hook my extension cable and aerial up to my card, the signal is WORSE? than without.

    Without the external aerial I can see MORE APs than when i plug the extendor in, and put the aerial outside my window.

    Does the LENGTH of cable matter? or is it just a duff aerial.

    Thanks
    It absolutely does, especially in the 2.4ghz range that Wifi operates on. Longer cable means more attenuation of the signal. Plus, each connector in the path adds attenuation.

    Card -[<- Extension -[<- Antenna cable

    in that configuration you've attenuated your signal through the extension as well as through two extra connectors.

    You really want to keep the number of connections down when dealing with Wifi, especially at the low powers that are used.

    If you do need to use an extension or need longer cable, then get the good stuff, like LMR-400 or better.
    A third party security audit is the IT equivalent of a colonoscopy. It's long, intrusive, very uncomfortable, and when it's done, you'll have seen things you really didn't want to see, and you'll never forget that you've had one.

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    Senior Member Thorn's Avatar
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    Quote Originally Posted by mcai8rw2 View Post
    OK, so i have an Edimax 7318USG USB adapter for use with BT3. The good thing about this adapter is that it has an external aerial socket.

    I bought a length of "extension cable" that would allow me to put an aerial further away than I would normally get with a plain old aerial.

    I would love for someone with some knowledge of aerials to tell me *why* when i hook my extension cable and aerial up to my card, the signal is WORSE? than without.

    Without the external aerial I can see MORE APs than when i plug the extendor in, and put the aerial outside my window.

    Does the LENGTH of cable matter? or is it just a duff aerial.

    Thanks
    Without going into a bit of RF theory, suffice to say that just like other things, length matters. Understand also, that some signal is ALWAYS lost in the cable. This is called attenuation. In your case, there is no doubt that you are killing off a significant portion of your signal.

    The idea is to gain more signal via the antenna, than is lost in the cable.

    RF cable is actually VERY finicky. The type, diameter, and impedance all influence how much attenuation occurs. That's why RF types (freq geeks) tend to carry all sorts of meters and other devices with them, to eek out the last possible millivolt from the cable.
    Thorn
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    Default Thanks to you both

    Thank you Thorn and Streaker for you informative answers,

    My extension cable is approx 10m long. That, plus the 3 connectors... I now understand why there was no improvment in the signal quality using the cable.

    Thanks again.

  5. #5
    My life is this forum Barry's Avatar
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    It's a usb adapter, so use a longer usb cable. That part is only limited to the limit of usb, which is around 16 feet.
    Of course, if you really wanted to have some fun, go to Wal-Mart late at night and ask the greeter if they could help you find trashbags, roll of carpet, rope, quicklime, clorox and a shovel. See if they give you any strange looks. --Streaker69

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    Very good friend of the forum Virchanza's Avatar
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    If the signal is analogue, the longer cable will just result in signal attenuation at higher frequencies (the cable acts as a low-pass filter). The idea is that you put the aerial in such a place that the stronger signal will counteract the loss in the cable.

    If the signal is digital, it's a lot worse, you'll get attenuation along with slurring of the square wave and also intersymbol interference.

    At the moment I've got a 5-metre USB extension lead for my Alfa and a 9-metre extension lead for my aerial, and sometimes I get "100%" signal.
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    Senior Member streaker69's Avatar
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    Quote Originally Posted by noway View Post
    itink it's effect
    Are you going to actually post something useful?

    We've already answered this thread to the OP's satisfaction. It would appear, you're just attempting to increase your post count with post after post of mindless blather.

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    Quote Originally Posted by streaker69 View Post
    Are you going to actually post something useful?

    We've already answered this thread to the OP's satisfaction. It would appear, you're just attempting to increase your post count with post after post of mindless blather.

    User Reported.
    You beat me to the punch I was looking at the user profile and noticing that the majority of the OP's posts contain about 3 words each.
    To be successful here you should read all of the following.
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    Failure to do so will probably get your threads deleted or worse.

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