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Topband: Bowtie Flags

To: <topband@contesting.com>
Subject: Topband: Bowtie Flags
From: Dennis W0JX via Topband <topband@contesting.com>
Reply-to: Dennis W0JX <w0jx@yahoo.com>
Date: Sun, 11 Dec 2016 22:00:12 +0000 (UTC)
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Mike and Don,

I have been using an expanded version of a DHDL here since November 2011. I was 
forced into going this way because the neighborhood around me has become very 
noisy and the antenna seems to be less susceptible to noise than my other 
antennas. I call it the Dual Flag array. I essentially expanded the DHDL deltas 
into the shape of a flag. My flags are large, approximately 24.5 feet tall and 
32.5 feet long and separated by three feet. The wires cross in the middle 
rather than at the bottom so the flags are 180 degrees out of phase. They are 
similar to a Waller Flag antenna in some respects.

My dual flag antenna is supported in the middle by a 31 foot pole made up of 
military fiberglas poles and the ends are supported by two trees. The bottom 
wire is 6 feet above ground. The feed transformer was wound on a binocular core 
with two turns on the primary and 7 turns secondary giving 918 ohms when fed 
with 75 ohm cable. I think my load resistor is 1290 ohms at the back of the 
second flag. You can put a variable pot there and tune for best F/B but that is 
not necessarily the best RDF.

I have found my dual flag array to be the quietest RX antenna in my RX system. 
It works very well on 160 through 40 although the pattern turns broadside on 40 
meters. It beats all my 450 foot beverages hands down and is a great compliment 
to my HiZ 4 square which is now on the main RX of the K3 with the dual flag on 
the sub RX. You can also build a switching system to reverse directions but the 
circuit is rather complicated so I have two of these dual flag antennas pointed 
in different directions. I manually switch directions by moving the 
transformers and loads around using banana jacks when really need to grab a new 
country.

As with all antennas of this type, an effective common mode choke at the feed 
point is an absolute must.SInce a rotatable version would be very difficult to 
build and support on a tower, the next logical step would be a smaller true 
Waller Flag like NX4D's Big Waller.

I must give credit to George AA7JV who modeled this antenna for me and provided 
the inspiration through his TX3A DHDL RX antenna.

73, Dennis W0JX 
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