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Re:: EFHW tuner

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  • cloud runner
    I remember reading that trying to keep the common mode off the coax is not a good idea in this instance. Further, keeping the coax short IS a good idea. In
    Message 1 of 2 , Mar 29, 2013
      I remember reading that trying to keep the common mode off the coax is not a good idea in this instance.
       
      Further, keeping the coax short IS a good idea.  In fact, I often use no coax at all, mount the radio on the pole with direct connection, but right now am using a five foot piece of RG-174.
       
      Am getting ready to do some tests on tuner efficiency.  Getting a match isn't always a good thing.  it may be a dummy load ;-)
       
      fred - kt5x
       
       

       

      Also, has anyone tried using an isolation transformer three feet down from a EFHW antenna to isolate the common mode RF that limits deployment to short lengths of coax, or would several turns of RG-174 around a toroid be sufficient to isolate the antenna from common mode currents as well?  I don't always want to have to be stuck feeding the thing very close to the tuner.

      Thanks,
      Chris KQ6UP
       
      .

    • Chris Maness
      Yes, there needs to be a small counterpoise. The common mode on the coax is the counterpoise, so I was suggesting putting the choke at three feet from the
      Message 2 of 2 , Mar 29, 2013

        Yes, there needs to be a small counterpoise.  The common mode on the coax is the counterpoise, so I was suggesting putting the choke at three feet from the antenna so that longer there is still some common mode current.

        Chris KQ6UP

        On Mar 29, 2013 8:48 AM, "cloud runner" <just.one.hill@...> wrote:


        I remember reading that trying to keep the common mode off the coax is not a good idea in this instance.
         
        Further, keeping the coax short IS a good idea.  In fact, I often use no coax at all, mount the radio on the pole with direct connection, but right now am using a five foot piece of RG-174.
         
        Am getting ready to do some tests on tuner efficiency.  Getting a match isn't always a good thing.  it may be a dummy load ;-)
         
        fred - kt5x
         
         

         

        Also, has anyone tried using an isolation transformer three feet down from a EFHW antenna to isolate the common mode RF that limits deployment to short lengths of coax, or would several turns of RG-174 around a toroid be sufficient to isolate the antenna from common mode currents as well?  I don't always want to have to be stuck feeding the thing very close to the tuner.

        Thanks,
        Chris KQ6UP
         
        .



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