• I use calibrated RF cables at work all the time. I'm lucky in that I have a spectrum analyser with a built-in calibration function!

    Anyway, I thought some of you might be interested in seeing what some real cable losses look like.

    You might think that when someone gives you a figure of say 2.1 dB loss, that that is the loss across the entire 2.4 GHz band. Not so! And below are some values that show this.

    To make this kind of a product evaluation, I took these measurements from a Trendnet, model TEW-L202, 2 meter long cable. This cable has a Reverse Polarity connector on one end, and N on the other.

    The actual data was reported to 5 decimal places, but for the purpose of this post I'll round to the nearest 1/10 db.

    CH Loss (dB)
    1 1.8
    2 1.8
    3 2.0
    4 2.2
    5 2.5
    6 2.7
    7 2.7
    8 2.5
    9 2.1
    10 1.8
    11 1.7
    12 1.8
    13 2.0
    14 2.3

    Avg. 2.1

    If you plot this data, you'll find a semi-sinusoidal pattern. Try it, you'll like it. Sorry, I can't post my Excel plot here.

    Lest you think these are poor loss values, or are not representative of any other cable, I'll tell you right now these are pretty repectable values for this type of cable.

    For my purposes, I don't need a super low loss cable. I just need one that is calibrated, and stable.



  • Wlanman,
    have you tried testing the same cable several times in various different deployment situations? I'd be curious what are the differences between say a 12" radius bend and a 1" radius bend.

  • Jon,

    Sorry, but no I haven't. This is a cable I need to keep in good shape, so it's not going to "get bent" any more than necessary.

    More tests like what you're suggesting are planned for the future though.

    I do have other cables (<4" long and .037" diameter) that were bent around small posts ~ 1/16" in dia. that increased their losses by over 8 dB !

    I also have some measurements for cables and their losses due to varying pin height. These were semi-precision custom cables, so the variation is VERY small, but it is still measureable (given that I can get 4 digits accuracy - hee hee).

    You can also see (with a microscope) where on one of them someone slipped with a wrench on the flat of one of its adapters, causing the connector to be set deeper - which raised the loss by over 10%.

    I need a more constant access to a network Analyzer, in addition to the Spectrum Analyser, to make a thorough study. The plots are still very interesting though.

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