[TowerTalk] Practical Ground Screens for NVIS antennas

Tue Jul 26 08:17:48 EDT 2005

Thank you all for your thoughtful and informative replies. Having a large 
spool of light wire with which I can easily lay down a screen is the easiest 
way to go, much like the pattern of cooling coils in AC heat exchangers. 
This avoids the tedious placement of individual wires.

I remember the 0.05 wave max spacing rule from past discussions of 
conventional ground radials. On 80m, our local Virginia Phone net and 
emergency net meets on 3947. During the day, there's also a 40m freq... 
hmmm. I would have to size the spacing for the smallest wavelength (40m 
band).

lessee....  (11811/7.2)*.05 = 82 inches.  A nominal 6 foot spacing ought to 
do it for both 40 and 80m. I'm not quite sure how much overlap (lengthwise) 
to use. A halfwave on 80m is about 135 ft in wire.

Let me attempt some ASCII art to illustrate. How about something like this ?

(~6 ft spacing)
   |  |--|  |--|
   |  |  |  |  |
   |  |  |  |  |
   |  |  |  |  |  (abt 140 ft length)
   |  |  |  |  |
   |  |  |  |  |
   |_|  |_|  |

or (even easier), just zig-zags:

\   (6ft)   ^            ^            ^   ---------------------------^
  \          /  \          /  \          /  \                             |

|
   \        /    \        /    \        /    \                            |

|
    \      /      \      /      \      /      \                         (abt 
140 ft)

|
     \    /        \    /        \    /        \                          |

|
      \  /          \  /          \  /          \                         |

|
       \/            \/            \/            \   ---------------------V

Thanks - Mark