It's taken me almost a year, but I've finished constructing and comparing
all four of K6SE's ground independent RX antennas. The following is a
summary of the performance of those antennas operated at my QTH.
OUTPUT LEVEL or "forward gain". This is important because it controls how
much coax loss (among other things) that you can tolerate between the
antenna and the preamp. Ranked highest output to lowest:
1) Flag
2) Pennant
3) Delta
4) Diamond
No secrets here, it's just as the models predicted. It's interesting to
note that the first three have sufficient output level to show no S/N
degradation with 350 feet of RG6/U between the antenna and preamp, but the
Diamond showed a bit with only 250 feet in the same setup.
DIRECTIVITY or F/B ratio. No ranking needed here. Under ideal conditions,
they all preformed about the same.
SUSCEPTIBILITY TO RE-RADIATION. This was a bit of a surprise because the
models didn't show the practical results. All four types exhibited similar
susceptibility to a nearby resonant vertical as would be expected. They
surprise came from the wide range of susceptibility to 1/4 wave elevated
radials and other horizontal structures such as fences. Ranked in order of
least susceptible to most:
1) Flag
2) Pennant
3) Diamond
4) Delta
The Delta turned out to be completely unusable when erected anywhere on the
property unless all the elevated radials were dropped and the fences were
more than 75 feet away. The Flag showed NO interaction with the elevated
radials at all even when erected right between them! The pennant showed
very little, but the Diamond had noticeable pattern degradation.
EASE of CONSTRUCTION and INSTALLATION. Rather subjective, but ranked
easiest to hardest:
1) Delta
2) Diamond
3) Pennant
4) Flag
As is always the case, "There is no free lunch!". The Flag configuration is
the hardest to construct but is overwhelmingly the best performer. I wanted
to use the easiest to build type, but just could not stand the performance
degradation experienced when anything but the Flag was installed at my QTH.
Other QTH's may have different conditions and other builders may have
different requirements, but my time and money goes into Flags every time.
I now have three of them up. One rotatable, and two others phased
broadside, spaced 285 feet, pointed 270°. This array will be moved and
pointed about 60° later in the season.
Still on the things to do list is a K9AY loop. It's harder for me to
evaluate because the structure is taller and the ground won't push around
the property!
73,
Larry - W7IUV
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