f81c9ded   
   From: lumpy@digitalcartography.com   
      
   miso@sushi.com wrote:   
   > I can't say I've ever seen a big J-pole...   
      
   Very, very common for AM broadcast and shortwave.   
      
   It's much safer for lightning strike protection.   
   The element is DC grounded.   
      
   Typically an AM broadcast band array will be   
   several shunt fed verticals in a phased array,   
   like the CB twins on an 18 wheeler (only the CB   
   antennas aren't jpoles). That way they can change   
   the feed phase and adjust the directional   
   characteristics of the array to comply with FCC   
   or whatever governing body there is in their country.   
      
   The KFI article mentions a "top hat", a capacitive   
   bunch of metal which allows the vertical element to   
   appear longer than it is (longer in RF wavelength).   
   Hams do that all the time. They mount their yagi beams   
   on top of their tower. Then when they want to work   
   160m or other low freq's, they load the tower as the   
   driven element, and allow the yagi to serve as   
   a cap hat, making the element appear longer to   
   the transmitter.   
      
   > I still say the tower top looks like a plus symbol   
      
   I'm not talking about the air conditioners on top.   
   I'm talking about the shape of the structure. It's   
   three sided. Like a typical shed/garage/hanger is   
   4 sided, this thing is three sided. It's floor plan is   
   a triangle that's a bunch of stories high.   
      
      
   Lumpy   
      
   In Your Ears for 40 Something Years   
    www.LumpyMusic.com   
      
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