Don,
The 64,000 dollar question: After adding the preamp, what is the 'effective'
sensitivity compared to station receiver?
For instance, using the Coastal Navigator DF receivers (that exhibit a
very useful unidirectional cardioid pattern that has a sharp null to the
rear) I can hear powerline noise above S7, in the S8 or stronger range
as shown on the Icom 756Pro3 station receiver connected to a
vertically-polarized antenna (a QW, 120 ft circumference, tuned loop).
A noise in the S9 or greater range on the IC-756ProIII is very easy to
pick up and locate with the Coastal Navigator receivers.
The wideband design of your design is a fantastic asset to tracking this
stuff down too, and the use with 50 Ohm input receivers (including
Spectrum Analyzers and lab-type impulse/EMI receivers) is a plus too.
73, de AA5CT Jim
.
.
On Thursday, February 20, 2020, 9:46:42 AM GMT-6, Don Kirk <wd8dsb@gmail.com>
wrote:
Numerous people asked for information about my portable terminated flag
that I built for MF/HF direction finding since it's unidirectional and here
is a link to a simple website I created to show my initial design.
https://sites.google.com/site/portableflagantenna/
My design may look crude, but I needed something quick, simple and cheap
for help in tracking some noise at the QTH of Mike (W9RE). A lot of
thought went into the design based on maximum allowable size for transport
in my car, minimum acceptable front to back ratio at very low elevation
angles, frequency coverage, complex impedance, gain (or lack thereof), etc.
The antenna has very negative gain especially on the lower HF and MF bands,
but with the appropriate preamp its become an extremely valuable tool.
It's much simpler and robust compared to anything else I could find. I had
been considering a sense antenna for use with my tuned loops, but wanted a
much less complicated system and the portable terminated flag has
definitely filled my immediate needs.
Flags and Pennants just want to work, and my small design is no exception.
Hope this initial info satisfies folks that had an immediate need for a
simple unidirectional antenna for DFing on MF and HF.
In the background I'm working on an article that includes a lot of charts
related to Front to Back Ratio Vs. Elevation Angle and Frequency, SWR vs.
Frequency, Gain vs. Frequency, etc.
Please don't laugh at the simplicity of my build.
Enjoy,
Don (wd8dsb)
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