Hi Mark: The tower (driven element) sits on a base insulator. So it is series fed.
73 Tim K3LR -----Original Message----- From: Mpridesti [mailto:mpride...@yahoo.com] Sent: Wednesday, January 31, 2018 4:46 PM To: k...@k3lr.com Subject: Re: Topband: Adding a parasitic reflector to a vertical Hi Tim Following this thread. Assume the tower is grounded so just how are you connecting your L network to the tower? A gamma wire? Tapped where? Appreciate your help! Regards, Mark, K1RX > On Jan 31, 2018, at 2:28 PM, Tim Duffy <k...@k3lr.com> wrote: > > I have been using a 3 element parasitic vertical beam on 160 for at least 20 > years. K9CT, NR5M, AA1K*, VE3EJ and most recently W5ZN have the same array. > It has instant switching in 4 directions. > > With 4 parasitic cut directors around the center driven element tower - it > is pretty easy to get over 5 dB of forward gain (over 40 KHz wide) and over > 30 dB of front to back (over a narrow bandwidth). Easy driven element match > with an L network at the base. Each parasitic has 3 modes. Director, > Reflector or float. Going from directional to Omni is easy as well. > > *AA1K has an additional director toward Europe. So he has 4 elements! > > As was pointed out - the magic in any vertical antenna is all about the > radials. Each parasitic wire (4) and the center driven element tower has 120 > radials that are 130 feet long (unless they cross the junction bus). I have > 67,000 feet of radials under my 160 array. > > I use a 120 ft 24 inch face solid leg tower as the driven element. The tower > sections are welded together to decrease any joint loss. The parasitic T > wires are #12 Copperweld. > > The last three editions of the Low Band DXing book describe this antenna in > the Yagi chapter. > > 73 > Tim K3LR > > -----Original Message----- > From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of W7RH > Sent: Tuesday, January 30, 2018 11:39 PM > To: Topband > Subject: Re: Topband: Adding a parasitic reflector to a vertical > > I've played with parasitic elements in antenna arrays for almost three > decades and the current antenna system I have used parasitic elements > both director and reflectors. > > With very careful tuning performance that of a all driven array can be > achieved. Tree is correct they due tend to be somewhat limited in in > bandwidth with relation to F/B ratio. Gain remains fairly constant. > > The tuning procedure that Tree suggested is absolutely correct. You > detune all unused elements and adjust the center frequency of the > parasitic for best F/B one element at a time. Parasitic elements I might > add are no different than driven and must have extensive ground system > to be effective. No exceptions. You know you have right by F/B ratio. > You can go one step further and measure the actual antenna currents > which I have done. In my system the parasitic elements achieve 80-85% of > the theoretical current at the base. > > de Bob W7RH > > > > > > > > > > > > > > > > -- > W7RH DM35OS > > > It has become appallingly obvious that our technology has exceeded our > humanity. > > Albert Einstein > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband