In a message dated 05-01-14, Roy Witt said to Holger Granholm:   
      
   Good morning Roy.   
      
    HG> Roy, you are confusing the issue. While Tom is correctly writing   
    HG> about director lengths you are suddenly writing about radials.   
      
   RW>What's confusing about that? Directors are radials and vice versa...   
      
   Nowhere have I heard or read that a Yagi antenna has radials.   
   A yagi has a driven element and parasitic elements of which the ones in   
   front are named directors and the one(s) behind the driven element are   
   named reflector(s).   
      
   RW>The other issue is that Tom is thinking that a yagi and a LPA are   
   RW>one and the same antenna, when in fact they are two different   
   RW>designs and each is engineered differently.   
      
   Agreed.   
      
   RW>i.e. The LPA antenna normally consists of a series of dipoles   
   RW>(directors, radials) positioned along the antenna axis, which are   
   RW>spaced following a logarithmic function of the frequency.   
      
   Actually there are two different kinds of log periodic directive   
   antennas.   
      
   The LPA antenna you are writing about has several driven elements that   
   are fed by crossing the feed to every element next in line. The lengts   
   of the driven elements are staggered to achieve a broader bandwidth.   
      
   I know this type particularly well because I have built and measured   
   several concepts for both 2 m and 70 cm and used them actively.   
      
   Behind the stack of driven elements there usually is a reflector and in   
   front of the driven elements directors. This antenna is often called a   
   KLM-yagi because the KLM company was the first to manufacture antennas   
   of thes kind originally presented in an article in QST.   
      
   The other kind of LPA is one built on two booms insulated from each   
   other and fed from (often) the front end. The elements are not dipoles   
   per se but are quarter wave length directors staggered on the twin booms   
   so that each director is only half of a director the second half of it   
   being placed where the next director (in a yagi) should have been.   
      
   73 de Sam, OH0NC   
      
   aka Holger   
      
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