Hi Larry,
Unless we A-B an antenna time and time again against a known
and stable reference and average the results, small or even modest
changes are lost in the data clutter.
> you want. In a practical installation, the two horizontal wires are seldom
> horizontal. If the wires are drooped down to a point near ground level at
> the ends, and the lengths adjusted to maintain resonance, the feed point
> impedance drops a lot. So much so that it looks like matching and real
> ground losses will more than make up any difference between the wires
> solution and the center coil solution.
I never looked at data for two wires, but four wires at 45 degree
angle with no perimeter wire will reduce the effective height of a 70
foot self-resonant 160m vertical to 60 feet compared to the ideal
case of a flat hat. In this case effective height is reduced only about
50% of the lowest height of the sloped wires (the bottoms of those
wires are at 50 feet). The system clearly does not lose all of the
height to the lowest point of the hat.
Look at this direct comparison for 1.835MHz resonance with #12
wire (except the 99ft high wire needs loaded to cancel power
factor):
70ft vert x4 22ft wires =22.8 loop Radres
70ft vert x4 45deg 28ft wires= 18.4 loop Radres
60ft vert x4 29ft wires=18.6 loop Radres
99ft vert x0 hat=18.3 loop Radres
A 70 foot vertical with four 45deg hat wires is equal to a 99ft vertical
for loop radiation resistance. A 60 foot vertical with four flat hat
wires is equal to the same.
Using the hat wires for guying certainly isn't a big problem, and the
effective height winds up being much taller than not using any hat
wires at all! Using guy lines as a way of increasing the electrical
height definitely works...and works very very well even if you slope
the wires at 45 degrees.
> It looks to me like drooping wire "hats" create as many problems as they
> solve. So, is this real?
Anything creates problems if done incorrectly. Using guy wires for
loading is an effective way to increase bandwidth and electrical
height, even though the wires are sloped. It is best to use multiple
wires, and avoid fold the wires in at angles significantly sharper
than 45 degrees, but you really have to get to an extreme to have it
not help.
Of course the better the ground system and loading coil, the less
difference changes in loop radiation resistance (height, loading,
etc) will make in signal strength! With poorer grounds and
increasing los in loading coils, changes in radiation resistance have
a larger effect.
73, Tom W8JI
W8JI@contesting.com
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