Hi Nick The wire will reduce loss on the transmission line given a better match and phase. In practice you can see change on the SWR and front back. If you have a good ground you probably won't see anything changing.
Regards JC -----Original Message----- From: Nick Hall-Patch [mailto:n...@ieee.org] Sent: Monday, December 12, 2016 10:59 PM To: JC <n...@comcast.net> Cc: 'topband' <topband@contesting.com> Subject: Re: Topband: Twist a Flag into a Bowtie? What kind of improvement in performance is observed by providing a better ground, JC? And, where would a ground wire (counterpoise?) be connected with the DHDL antenna system? Thanks and 73, Nick VE7DXR At 15:38 11-12-16, JC wrote: >Hi Mike and Don > >The DHDL as well as few other antennas, has a hidden component. The >bottom wire parallel to the ground is a transmission line, actually, >any antenna parallel to the ground is a transmission line. A beverage >antenna a is good example. > >The ground is the second leg of the transition line, for a K9AY loop >it is the same, the bottom wire and the ground form a transmission >line. The transmission line allows the Resistor and the Transformer to >be moved to the center of the loop. The VE3DO loop is also exactly the same. > >The same way, a DHDL antenna uses the ground to phase the two loops, if >you elevate the DHDL high far from the ground, the patter changes. The >DHDL is a ground dependent antenna, improving the ground with a ground >wire bellow the antenna can fix some ground problems. > > >My two cents. > >73's >JC > >N4IS > >-----Original Message----- >From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Don >Kirk >Sent: Sunday, December 11, 2016 10:13 AM >To: D Michael <damich...@verizon.net> >Cc: topband <topband@contesting.com> >Subject: Re: Topband: Twist a Flag into a Bowtie? > >Hi Mike, > >Funny you should ask that. > >A few months ago (September) I was looking at building a smaller size >DHDL using 4Nec2, and there were a few things I saw that I thought >needed improvement (I saw things in the full size DHDL that I thought >needed improvement, it was not limited to the small size DHDL I was >trying to design). Then I started to play around with the location of >its termination resistor as well as routing of wires, and wound up with >what I called the Terminated Bowtie. I built one in my backyard but my >yard is pretty small and the antenna was too close to existing objects >(house and chain link >fence) and I did not realize the S/N improvement that I expected, >nevertheless based on modeling it looks like a winner (9.5 RDF and >front to back ratio versus elevation angle very robust). > >I have attached the preliminary document I put together a few months >ago for you and others to view (it might not be perfect, but should >convey my design / thoughts). I would love someone to build one of >these out in the open to see if the real life build provides results >similar to the 4Nec2 modelling I did. > >Note: Bringing the feedline away from the antenna properly needs to be >looked at to minimize distortion of the pattern. As I recall the >feedline should not drop down to the ground until it's at least 5 feet >away from the antenna, and a greater distance would be best. The >feedline should also use choke with ground rod similar to what's >recommend for other RX antennas we use (beverages, flags, etc.) to >block common mode noise from making its way to the antenna feedpoint. > >Let me know what you think. It might not work, but sure looked good on >paper. > >73, >Don (wd8dsb) > >On Sun, Dec 11, 2016 at 9:41 AM, D Michael <damich...@verizon.net> wrote: > > > > > > > I have two flag rx ants and I was looking at the DHDL and DK6ED > > Double Loop System V2 and wondering if twisting my Flag rx ants into > > Bowties would improve the forward pattern and make them narrower > > with better front to back. > > I would just ""flip"" the termination resistor end to form a loose > > BOWTIE shape. > > I have no ant modeling software so I have no way to ponder this change. > > Maybe someone could model doing this. > > TNX es 73, Mike W3TS > > _________________ > > Topband Reflector Archives - http://www.contesting.com/_topband > > >_________________ >Topband Reflector Archives - http://www.contesting.com/_topband > >_________________ >Topband Reflector Archives - http://www.contesting.com/_topband Nick Hall-Patch Victoria, BC Canada _________________ Topband Reflector Archives - http://www.contesting.com/_topband
