Greetings TOM!   
      
      
    RW> TW>> I have one of the antennas I am talking about on my roof   
    RW> TW>> constructed from the Pure Origional LDPA theory drawing,   
      
    RW>> You mean the schematic of such an antenna. Pure LPDA is built with   
    RW>> two booms and follows a formula, which is where the LP comes from.   
      
    TW> All antannas are built form some Schematic or theory Drawing aren't   
    TW> they?   
      
   Not always...I have the makings of a LPDA in my shop, that will require me   
   to cut the elements as I assemble them to the booms. The only drawing is   
   one that I used to help me see it in my mind. No theory, just lengths and   
   spacing dimensions from an experimental antenna built years ago.   
      
    TW> Well when you stand above the antenna I am talking about it looks   
    TW> just like the theory drawing and uses the Same Formulas of the LPDA   
    TW> antenna so how can it NOT be an LPDA antenna?   
      
   Because it isn't. What you may think is a LPDA when you look at it, is   
   actually called a 'bandpass yagi' in KLM's book.   
      
    TW> As I mentioned the Two boom implimation was only used to make the   
    TW> antenna easier and cheaper to manfacturer.   
      
   Wrong. The boom is an integral part of the LPDA and only a neeessety in a   
   yagi with insolated elements. i.e. the LPDA boom affects the 'excited'   
   part of the antenna, while in a yagi, everything but the driven element is   
   parasitic.   
      
    TW> But no all manfacturers did so.   
      
   If they wanted to have someone believe their product was an LPDA, then   
   they built it accordingly.   
      
    TW> And it is Not the booms that make it a "Dipole Array" but the dipoles   
    TW> themselves differing in size and all being connected to the feed line   
      
   It is the booms that make it a "Log Periodic"...and not one LPDA is feed   
   with anything but coax to the booms.   
      
      
   The antenna you speak of is a "bandpass yagi". The one I have of their   
   models is called - KLM-27el-UHF-BandPass-Antenna, Model KLM-420-470-27.   
      
   The model number speaks for the antenna;   
      
   Manf - KLM * Band - 420-470MHz * Elements - 27 * Length 120" aka 10 Feet.   
      
   It has 4 elements that are considered to be LPDA, while it has 23   
   parasitic elements that are called directors with one reflector.   
      
   Each director and reflector element are one piece, like a yagi.   
      
   The 4 element 'dipole array', are seperated and fed with the cross links   
   as you describe, but the factory labels them as 'phasing straps'...   
      
   Since the directors and reflector are insolated from the boom as well as   
   the driven elements, the boom doesn't do anything but support the   
   elements. BTW, the mounting or balance point is between director 13 & 14   
   using a non-insulated metal plate. If you did that to a LPDA, the antenna   
   would be shortened physically and electronically, if it worked at all.   
      
   So, the antenna has a LPDA section, but is called a yagi by KLM, the   
   manufacturer, it's only relationship to a true LPDA is the fact that it   
   has an excited area of 4 dipoles in a true LPDA array. But, because of all   
   the parasitic elements, it is merely a yagi.   
      
      
       Have a day!   
      
            R\%/itt - K5RXT   
      
   --- GoldED+/W32 1.1.5-31012   
   --- D'Bridge 3.99   
    * Origin: HAM Radio, aka Amateur Radio. 804? Over! (1:387/22)