Topband: Twist a Flag into a Bowtie?

[Nick Hall-Patch]

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-bounces at contesting.com] On Behalf Of Don Kirk
>Sent: Sunday, December 11, 2016 10:13 AM
>To: D Michael <damichael at verizon.net>
>Cc: topband <topband at 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 <damichael at 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
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> >
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Nick Hall-Patch
Victoria, BC
Canada