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The J-pole antenna is an end-fed omnidirectional half-wave antenna that is matched to the feedline by a shorted quarter-wave parallel transmission line stub. [5] [1] [6] For a transmitting antenna to operate efficiently, absorbing all the power provided by its feedline, the antenna must be impedance matched to the line; it must have a resistance equal to the feedline's characteristic impedance.
Parallel-wire line (the generic sense of twin lead) is supplied in several different sizes, with values of 600 Ω, 500 Ω (ladder line), 450 Ω, 350 Ω (window line), 300 Ω (window line, ribbon cable), and 75 Ω (ribbon cable) characteristic impedance.
All along the post, along the spine, there are studs or nubs that prevent the barbed wire or mesh from sliding up or down the post. They are generally designated as 1.01, 1.25 or 1.33, referring to the weight in pounds per lineal foot. They are commonly painted with a white tip on top; white improves the visibility of the fence line.
The rod, perch, or pole (sometimes also lug) is a surveyor's tool [1] and unit of length of various historical definitions. In British imperial and US customary units , it is defined as 16 + 1 ⁄ 2 feet , equal to exactly 1 ⁄ 320 of a mile , or 5 + 1 ⁄ 2 yards (a quarter of a surveyor's chain ), and is exactly 5.0292 meters.
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At this scale, the width of a human hair is about 10 times that of the image. [79] To help compare different orders of magnitude, this section lists lengths between 10 −7 and 10 −6 m (100 nm and 1 μm). 100 nm – greatest particle size that can fit through a surgical mask [80] 100 nm – 90% of particles in wood smoke are smaller than this.
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The Shellrock bed of the Jetmore Limestone member (marker bed J-13, 17–20 feet (5.2–6.1 m) below the Fencepost) is broadly similar to the Fencepost; and of the other limestone bed in these units, it is the most frequently used unit after the Fencepost, both for fence posts and for building.