Greetings Holger!   
      
    HG> In a message dated 05-16-14, Roy Witt said to Ed Vance:   
      
    HG> Hi Roy,   
      
    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?   
      
    HG> All "these?" are driven elements cut to lengths for various   
    HG> frequencies within a specified frequency band.   
      
   Actually, they're all passive until either a received signal excites them   
   or a xmitted signal does. Usually, depending on the number of elements and   
   their lengths, there are active zones and inactive zones with at least one   
   of the 'elements' acting as a dipole and the elements fore and aft of it   
   acting as director and reflector, at that frequency.   
      
   If the frequency changes, so may the reactive dipole element.   
      
    HG> The booms are not a closed loop.   
      
   I realized that after it was sent already. Only you and I noticed it.   
      
    HG> The coaxial feeder is fed through one of the booms with both ends of   
    HG> the shield connected to the boom and the center conductor is   
    HG> connected to the other "boom" at the small end.   
      
   Never heard of that. The coax feeder is strung along the bottom of the   
   lower 'boom' and then the center conductor connected to the upper boom and   
   the shield connected to the lower boom at the forward end of the antenna,   
   aka the shortest element end.   
      
    HG> The outer jacket of the coax shall be removed for the entire length   
    HG> of the "feed through" boom and the shield be allowed to make contact   
    HG> with the boom anywhere.   
      
   That isn't general practice either.   
      
    HG> The booms must be isolated from the mast where it is mounted or a   
    HG> non-conductive mast should be used.   
      
   Correct.   
      
    HG> This antenna has been fully described in the Ham Radio magazine with   
    HG> element lenghts for various bands of frequencies.   
      
   Perhaps, but who reads magazines these days? Formulas for finding the   
   lengths of elements and booms are available on the internet and readily   
   used to design any LPDA for whatever use you have in mind. The only paper   
   you'll need is used as a notepad to write down the lenhths. All you take   
   to the workbench is the notes.   
      
      
       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)