Match Antenna to coax

Discussion in 'Wireless & RF Design' started by FusionState, Jun 2, 2015.

  1. FusionState

    Thread Starter New Member

    Jan 29, 2014
    3
    0
    I've taken the antenna out of a wireless internet box. It consists of 4 square panels on PCB, that meet at a junction point, (4 squares connected together). Each panel is about 2.5" sq. I've connected a length of coax to the panels and run this to a cell phone, then wrapped a few turns around the phone it self as an air gapped couple to the internal antenna of the cell phone. We were able to improve a little, the reception.

    The coax in question is: RG 6/u 18ga CATV. Nice stuff by the way but perhaps out of spec for 800 mhz.

    Question: How do I determine if and what values the RC network should be to match the cable to the antenna.
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    The chances of finding the answer to your question are virtually negligible without the "right" test equipment - such as a network analyser.
    I don't think using discrete RC matching networks will meet your requirements either.
    The antenna is probably a patch type microstrip design. It may well be designed for 2.4GHz. Is it a 50 ohm or 75 ohm design or some other impedance? Too little information to work with.
     
  3. MrAl

    Well-Known Member

    Jun 17, 2014
    2,423
    490
    Hi,

    What gave you the idea that you should use an RC network?
    I ask not to mock, but to find out if you found a legitimate reason for doing this.
    Normally you use a transformer, coil, capacitors, or a stub transmission line. Resistors loose power so you dont normally use them, you use active devices like coils and caps.
    You could probably find out more about this on line, i dont remember that much on this subject as i did not have to work with it in the past except for fooling around a little with the ideas.
     
  4. FusionState

    Thread Starter New Member

    Jan 29, 2014
    3
    0
    Thanks MrAI for the contributions. I don't have much experience in RF and only basic to intermediate electronic theory. The hunch to use RC matching networks is based on low frequency knowledge. In a day or so we'll try to see if this kluge works at all. As I mentioned, the number of bars improved but it is likely there will be considerable signal degradation due to reflections in the COAX. I'll drop a line once I get a chance to work on the set up again. This is for use in a rual area with no local cell tower. However, depending on atmospheric conditions and a little climb up the hill, reception is improved enough to make a call; so I though perhaps an antenna would work.

    Regards,

    fusionstate.
     
  5. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    You could try this simple approach if you have the right phone with an accessible antenna port ....



    One can probably purchase an antenna with the correct connector fitting to plug into the port.

    For instance, I have an older Samsung phone which has this feature ....

    Antenna Point on cell phone.jpg

    Not sure if this an actual antenna input....
     
    Last edited: Jun 4, 2015
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