Greetings TOM!   
      
      
    RW>> Here's a vertically polarized LPDA:   
      
      
    RW>>           + what are these?   
    RW>>           | +   
    RW>>           | | +   
    RW>>           | | | +   
    RW>>           | | | | +   
    RW>>           | | | | |   
    RW>>  closed|------------+----feed point   
    RW>>    loop|____________+----feed point   
    RW>>          | | | | |   
    RW>>          | | | | +   
    RW>>          | | | +   
    RW>>          | | +   
    RW>>          | +   
    RW>>          + and these?   
      
      
    TW> Directly fed elements.   
    TW> A normal YAGI only has one directly fed element.   
      
   A yagi has one boom and the "elements" are insolated from it. Also, a yagi   
   is cut to cover as much bandwidth as it can while using all of its   
   "elements" to direct, transmit and reflect RF.   
      
    TW> The advnatage of the LDPA is increased bandwidth but at the expense   
    TW> of antenna Gain.   
      
   LPDA antenna gain is commenserate within 2db with a yagi if tuned   
   properly. There are no free lunches in either design, but the LPDA will   
   have more bandwidth than a yagi.   
      
    TW> But it does make it possible for a single antenna to be used with   
    TW> wider range of frequencies at a reasonable SWR   
      
   Why is that? Because there are two possible scenarios. One being an   
   'inactive region' and the other being an 'active region'. Thus, in the   
   antenna above, each "element" can be active or inactive, depending on the   
   frequency in use.   
      
   If one of those dipoles is reactive to that frequency, the "elements" fore   
   and aft of it will act as director and reflector. Each contributing to   
   the radiation of the antenna.   
      
   The "elements" that are in the 'inactive regions', are too short and will   
   be too capacitive to radiate and those that are too long will not radiate   
   very well.   
      
    TW> Create sells 2 "similar"(the ones I was adressing in my previous   
    TW> posts) antennas one with a 105 to 1300 MHZ bandwidth and another with   
    TW> a 50 to 1300 Bandwidth with a claimed 2.0 SWR or less   
      
   Which one are you gonna buy?   
      
       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)