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:nhp@ieee.org]
Sent: Monday, December 12, 2016 10:59 PM
To: JC <n4is@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-bounces@contesting.com] On Behalf Of Don
>Kirk
>Sent: Sunday, December 11, 2016 10:13 AM
>To: D Michael <damichael@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 <damichael@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
> >
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Nick Hall-Patch
Victoria, BC
Canada
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