Two wireless devices with coaxial cable

Discussion in 'Wireless & RF Design' started by ivars211, Jul 25, 2016.

  1. ivars211

    Thread Starter New Member

    May 5, 2013
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    Might be really dumb question, but just curios. (couldn't find anything useful).
    Let's say I have two wireless devices, both have SMA connectors for external antenna. Can I connect them both with some form of coaxial cable together? Would they still work for like 100m, or would the signal be too week?
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    The problem is more likely to be that the signal would be too strong and swamp the receiver. A simple resistive attenuator would make it work.
     
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  3. BR-549

    Well-Known Member

    Sep 22, 2013
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    Coax is an attenuator. The amount of attenuation depends on coax type, frequency and length.

    A length of coax can make an excellent dummy load.

    Depending on that frequency and power level, you probably can't get a signal thru 100 ' of coax.
     
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  4. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    The attenuation of 100' of RG58 at 443MHz is 10dB so a 10dBm transmitter level may still be too much for -110dBm receiver.
     
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  5. ivars211

    Thread Starter New Member

    May 5, 2013
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    I am thinking of RFM69HW 868Mhz on both ends (tx @ +20dBm). 100m RG6 @ 868 has attenuation of 20dBm. I guess that's still too much power for receiver end?
     
    Last edited: Jul 25, 2016
  6. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    If you haven't got a spec for the receiver max input power it's difficult to say for certain. 0dBm may well be OK - it's not going to damage anything so you can try it and it's easy enough to add some a couple of resistors to reduce it if need be.
     
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  7. bertus

    Administrator

    Apr 5, 2008
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  8. ivars211

    Thread Starter New Member

    May 5, 2013
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    I figured, I can always reduce RFM69HW output power if needed. Thank you guys, much appreciated.
     
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