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Discussion in 'CB Antennas' started by Hotrod2020alabama, Aug 16, 2018.

  1. Hotrod2020alabama

    Mar 18, 2018
    Likes Received:
    Collinear antenna for cb band. I have thought about getting 2 spt 500 and put one up and then one down without the ground plane but how would I connect the two? 75 ohm coax cable or 50 ohm coax? Anyone got a way I could do this and it work?

  2. Shockwave

    Shockwave Sr. Member

    Sep 19, 2009
    Likes Received:
    Since a 5/8 wave antenna can be matched at 50 ohms with just an inductor placed in series at the feed point (no tap to ground), why not consider replacing the ground plane radials with another 5/8 wave radiator and matching inductor below the first? Then it's a balanced antenna where both coils can be fed with the coax through a ferite balun.

    People have been doing this for years with high impedance ladder line feeding the two 5/8 wave antenna sections but I think a pair of inductor coils at the feed point could directly match this collinear antenna to 50 ohm coax with just a balun added. Two Sirio Tornado 5/8 wave antennas without the radials would lend themselves well to this modification since their matching coils are not DC grounded.
    #2 Shockwave, Nov 8, 2018
    Last edited: Nov 8, 2018
    Shadetree Mechanic likes this.

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