On 10/19/2011 2:28 PM, shristov wrote: > > > Folding has nothing to do with either radiation resistance or ground losses. > It is impedance-transforming device only. > > You've just performed 1:4 impedance transformation, nothing else. > > 73, > > Sinisa YT1NT, VE3EA Sinisa, A well known broadcast consulting antenna group Mullany and Associates made a detailed NAB presentation in the 60's on why a folded unipole and a cage feed made significant improvements for stations with questionable ground systems. They presented FSM reading with and without to prove their point. From that point on it became sort of an urban legend. Other studies have discounted the claim completely. The acid test by du Treil, Lundin, & Rankin out of Sarasota, FL, was ungrounding and directly feeding a tower and hooking the cage to the feed point and getting exactly the same FSM reading at 1 mile with when the cage was fed unipole style! Their findings were presented at the 1996 NAB Broadcast Engineering Conference. The original Mulany papers in the early 60's suggested that by raising the feed point impedance less current was flowing in the ground system thus improving the overall efficiency. Many hams still believe that is still true. Thanks for the clarification. But the legend continues to have legs.
Herb Schoenbohm, KV4FZ _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
