Topband: 160-80 rotary bean antenna that really works

[n4is]

Hi low band lovers

 

I would like to share with you a rotary bean antenna that really works. I
built it two month and only during the holidays I was able to fine tune it
and enjoy the results.

 

The experience of using this kind of antenna is identical as using a 2
elements cubical quad or a 3 elements yagi on 20 m. The directivity is right
there, it has two 30 db deep nulls at each side. The front/back is close to
30 db and the front lobe usable for 30 degree each side. The antenna is very
quiet and rejects high angle very well, the main lob peaks at 20 degree
elevation, and the antenna is on top of my second tower at 50 ft high

 

This performance made my best Christmas present ever. The antenna is “Just
Fantastic”.

 

Well, the “Waller Flag”, as I called it,  is not a new antenna project at
all, the idea of it started with WA2WVL articles QST Feb,1995, about “Is
this Ewe for you” at the end of the second article, Floyd mentioned the new
design of a dual Ewe in end-fire, but no constructions or practical
evaluations details. Few years later, Earl K6SE QST July 2000, working with
EA3VY come up with an improved project ground independent Low Band Receiving
Antenna and Earl called it “Flag Antenna”.  Earl also presented the project
of two flags in phase with a nice diagram. ON4UN also mentioned the project
idea on his book.

 

Three years ago Doug Waller, NX4D living on 1/3 city lot put a goal to work
as many DXCC on low bands as possible from his limited size lot. First he
built a rotatable flag and started to improve the project, Doug figured out
the possibility to build two small flags in end fire configuration. He
followed most of Earl’s recommendations on his article.

 

I learned about Doug’s Dual Flag, the guys here in Florida called the
antenna “Waller Adcock”, only few month ago and I jumped into this project
right way. Doug worked 5 Bands WAZ and over 208 counties on 160 m on the
last 5 years. More impressive was that Doug heard over 260 countries with
his dual flag antenna.

 

There is no “free beef” on top band.

 

First it was necessary  to detune my tower because I learned it in the hard
way, since I got my vertical full size, my Ewes just stopped  working, I
just lost they, before with my vertical at 85ft the Ewe’s always received
better then my vertical. 

 

I chose to transform my shunt feed vertical into a SKIRTED UNIPOLE and using
a detuning relay disconnecting the Skirt from the tune circuit I was able to
recover the reception on my Ewes. The Skirt works like a ¼ wave coax
transformer, it is grounded on the top of the antenna and open at the
bottom, so it has high impedance at the base. The skirt tunes at the exactly
at ¼ wave with a small 37 pF doorknob capacitor.

 

With my TX antenna properly detuned the noise level on my Ewe’s dropped 2 S
units just. The full size vertical was reradiating all that noise into my
receiver antenna.

 

Using the antenna is the best way to evaluate the performance, any time you
turn it you can see how the antenna is receiving signal A or dropping signal
B, but I found a way to measure the diagram using a program form G4HFQ, My
IC-7800 ha a SDIF audio output connected to high quality sound blaster.
South of me there is BC AM station on 1700 KHz, The signal is quite stable
early in the morning so I am able to measure my new antenna and do
improvements based on measurements results. This taking in considerations
the several errors that this system my have. The results are very impressive
but compatible with on air tuning using the antenna,

 

The RDF of the Dual Waller Flag antenna is 11.6 db, depending is you tune it
for max RDF it can reach 11.8 db, tuning for best Front/Back the RDF drops
to 11 db. I’m using 180 phasing line and R1=750ohms and R2=766 ohms. The
EZENEC Azimuth diagram is very close to 1.75 wave beverage and the
measurements I’m taking shows a 76 degree 3db angle. The beverage elevation
lob angle peaks at 40 degree and the Waller Flag peaks at 20 degree. The
diagram is very close to a well built 4 SQ receiving array but it peaks at 8
degree on good ground.

 

The Waller Flag is ground independent and can be installed on top of any
tower, even at 200 ft high if you want.

 

This does not com

 

You can see this project see in my simple web site. It is under construction
and I will upload the complete information to build it in few month, There
you can see the photo of my 160m vertical, Doug’s Walled Flag, my Big Waller
Flag, the chart at 1700 MHz with the antenna detuned and with no detune
effect, Very interesting plot. Also the diagram on 3.5 MHz, and 7 MHz, The
Waller Flag does not work on 40 m very well.

 

Sure I’m planning to test a small version for 80/40. I built my Waller Flag
bigger to avoid the use two preamps. I have a good signal level of using the
internal PRE2 on my IC-7800.but with a 20db external preamp the signal level
is very comfortable to work weak signals on 160m, 80m the WF has 20 db more
gain, so it does not need an external preamp at all.

 

www.n4is.com <http://www.n4is.com/> 

 

How to detune a tower on the NCJ website

 

http://www.ncjweb.com/novdec05feat.pdf

 

 

This project can be improved and I’m working on it. The ability to have a
rotary antenna on top of a 50ft tower can change your idea to buy 10 acres
just for beverages antennas. This is a working in progress but I’m exiting
to share project with the ham community. Any comments are welcome.

 

Regards

Carlos

N4IS (PY2DP)