WiFi Antenna Signal Cable Question

Discussion in 'Wireless & RF Design' started by cds333, Feb 25, 2015.

  1. cds333

    Thread Starter Member

    Nov 5, 2007
    16
    0
    So I am needing to set up a directional antenna for 2.4 GHz on the roof. The antenna will most likely be something like this. I am needing maximum range and directionality, so the high db antennae is not just to counteract the potential signal loss.

    The total cable length will be probably around 30-40 feet, and I was looking at a few attenuation charts, and it seems 9913 coax would be the way to go, from this site I found, although it seems there would still be some signal loss, up to 7db or so.

    So my question is: is there a better cable than 9913 coax, for WiFi frequency ranges, that's not prohibitively expensive...

    and... would it be better to just put the NIC card or router up on the roof right next to the antenna, and then run a powered USB cable down into the building? Can anyone think of any compelling reasons why to go with one way vs the other?

    (I realize I would have to weatherproof the enclosure and manage the heat in the summer)

    Thanks in advance!
     
  2. skeptic

    Active Member

    Mar 7, 2010
    51
    9
    I' go with putting the router on the roof next to the antenna. Have you checked the rules for the maximum EIRP you're allowed at that frequency?
     
  3. Papabravo

    Expert

    Feb 24, 2006
    10,147
    1,791
    To combat the high loss of coaxial cable at those frequencies you would normally use hardline with foam dielectric. As you have already observed, cost is a problem. USB cables don't operate at 30 to 40 feet that I aware of. High-Speed is 480 Megabits per second. I think you're between a rock and a hardline - so to speak.
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    you would probably have to run an eathernet connecton to the router to get the speed.
     
  5. Reloadron

    Active Member

    Jan 15, 2015
    963
    232
    When I experimented with this years ago I found the best way to go, in my case. was the router was beside the antenna on the roof. I finally used Belden 83265 50 Ohm Coax (RG-178) in a length of literally about a foot. Also had to consider the loss through my adapters. Tried various antenna designs both commercial and home brew and actually had my best luck with some "cantenna" type designs. This was all maybe 10 plus years ago. Anyway, best results were router at antenna. The best I managed was maybe 400 feet, line of sight unobstructed with a factory Linksys router, maybe it was a WRT54? Been a long time. It was ethernet to the router, either CAT5 or CAT6, I forget but that run was less than 100 feet.

    Ron
     
  6. cds333

    Thread Starter Member

    Nov 5, 2007
    16
    0
    Yeah I was planning on using my Alfa adapter, since it works so well with linux and is configurable up to 1W output power (2W on the new model). I was going to use an active USB repeater cable or perhaps a USB over cat5 to extend the effective range. When and if I need to host wifi from up there I'll set up the router which of course can just use the cat5.

    I'm not sure about the EIRP, if that's the same as the max output power I think that's set by region, and can be changed by using command line utilities in linux.

    Thanks so much for everyones input!
     
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    wifi is covered under the FCC part 15 rules. those rules say that wifi equipment must use the antenna it came with when type accepted. there have been $11,000 fines for not doing this.
     
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