An all-bands random wire antenna
by sv3ora



The multi-impedance transformer has 9 quadrifilar turns wound onto an FT240-43 toroid and connected as shown in the next schematic. The 9:1 tap is only used for the random wire antenna. Other taps are there is other types of antennas are to be tried in future time.



The choke has 18 turns of RG-142 coaxial cable, cross-wound (Joe Reisert method) onto an FT240-43 toroid.



The monopole antenna wire length should be one from the table below. The band column show the lowest band that the antenna can operate properly, with the corresponding length. Obviously, choose the longest length based on your available space.

band mt   wire meters  
--------  -----------  
   20         8.84        
   40        10.82        
   40        12.50        
   40        17.68           
   80        21.64           
   80        25.60        
   80        32.61       
   80        36.27       
  160        45.11          
  160        61.87       
  160       105.77       
  160       124.05       
  160       128.93 

You must also connect a counterpoise at the ground connection of the transformer, for the antenna to work properly. A good counterpoise for a random wire antenna should have a length of 1/4 lambda at the lowest operating frequency (which for the 160m band means 40m). Such a counterpoise may be just laid down on ground in a straight line and/or looped around, trying to keep the loop as large as possible. Alternatively it's possible to connect a run of wire from the counterpoise connection to the ground and, from there, run whatever number of radials of various lengths and in various directions.

Special thanks to my friend Andrea from Italy, for pointing me in the right directions in building this antenna!

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