EV>I couldn't find any A.R.R.L. Radio Amateur's Handbook that had info   
   EV>on DDRR antennas.  The latest issue I have is the 1976 Edition.   
      
   EV>I looked under DDRR, Directional, Disconnunity and Ring in the Indexes   
   EV>of all of the A.R.R.L. Handbooks I have -1957 through 1976- and didn't   
   EV>find any reference for those.   
      
   EV>They weren't mentioned in the Indexes of the 1964 A.R.R.L Antenna Book,   
   EV>nor in the 1962 and 1975 Radio Handbook by William Orr W6SAI.   
      
   Here is a good description of the DDRR Antenna   
      
   The DDRR (Direct driven ring radiator) was invented by Dr. Boyer from   
   Northrop, for military applications in the 50s. It stayed classified   
   until Dr Boyer published an article titled "Hula hoops antennas" in   
   Electronics (Jan 11, 1963). "73 Magazine" published also a two part   
   article from Dr. Boyer titled "Surprising Miniature low band antenna".   
   The article is quite technical and contains a very precise mathematical   
   formulation of the DDRR based on transmission line theory.   
      
   In layman's terms a DDRR is just a short vertical monopole (vertical   
   post) attached to a transmission line tuned by a reactance (ring plus   
   vacuum capacitor). The reactance of the capacitor is transformed by the   
   transmission line and will under specific conditions (length, value of   
   the capacitor, etc.) make the vertical post resonant. Slight variations   
   of the capacitor will lengthen or make the transmission line "shorter"   
   and allow tuning of the antenna on a certain range.   
      
   Boyer designed two basic models: the one ring DDRR and the two rings   
   DDRR.   
      
   The first one is made of an opened ring made of aluminum tubing (4 in.)   
   over the perfect ground of a metallic structure like a warship, and with   
   two aluminium posts connected at the extremities of the ring. A set of   
   fiberglass post supports the ring. One of the vertical post is attacked   
   at the base by the coax, the other one contains a variable vacuum   
   capacitor to tune the antenna. This faded picture from the 50s from   
   Northrop show a set of concentric DDRR for 2 to 30Mhz. The engineer is   
   standing below the 75m loop (6 feet height) and is looking at a 50Kv   
   vacuum capacitor. This type of DDRR was installed on some special   
   communication and ELINT warships, and was apparently used in the early   
   stages of the Apollo project.   
      
   The advantages of DDRR compared to a vertical are obvious, especially on   
   a ship. Small size and height, remotely tunable, low noise due to loop   
   structure, extremely low impedance and therefore no or little influence   
   on connected electronic equipment from voltage transients and lightning.   
   Low angle for long range communication and possibility of a secondary   
   high angle for NVIS, indispensable in fleet communications, can be   
   achieved by using a configuration using a central post and two posts   
   with vacuum capacitors.   
      
   The second type is a double ring system isolated from the ground with   
   the same two vertical posts connecting the opened extremities of the   
   rings. One is solid aluminium, the other one contains a Vacuum. A third   
   aluminium post cut in the middle is used to feed the antenna and can be   
   moved to adjust the SWR. The coax enter in the middle of the right post,   
   then up then down to the "feed point" where the shield is connected to   
   the top part and the center of the coax to the bottom part of the post.   
   This configuration creates a coaxial balun for a symmetrical attack.   
   Matching is achieved by moving the "feed point post".   
      
   Contrary to the one ring model, there is no need here for a perfect   
   ground and Dr Boyer was confident that this antenna could perform well   
   even on very poor ground. He referred in his articles to the fact that   
   DDRR are essentially "magnetic" antennas in the near-field and that   
   losses in the ground my magnetic field are negligible.   
      
   Tests made by Boyer and his team for Northrop and the US Navy showed   
   that the antenna was very low noise and very low angle. This was done in   
   side to side comparisons made with a collapsible vertical on 160m in the   
   Arizona desert, using a half square mile ground plane made of solid   
   copper sheets soldered together   
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