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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.
The most widely used types of feed line are coaxial cable, twin-lead, ladder line, and at microwave frequencies, waveguide. Particularly with a transmitting antenna, the feed line is a critical component that must be adjusted to work correctly with the antenna and transmitter. Each type of transmission line has a specific 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.
They are intermediate in size and function between small and large loops, and are often described as a half-wavelength dipole that has been bent from a straight line into a round circle, but with its far ends left unconnected. [3] [11] [2] [4] (pp 231–275)
By voting Trump back into office, voters “soundly repudiated Biden’s radical open borders policies” that “made less Americans safe,” said Texas State Rep. Brian Harrison.
Via fences use up a lot of valuable substrate real estate and so will increase the overall size of the assembly. Via fences too close to the line being guarded can degrade the isolation otherwise achievable. In stripline, a rule of thumb is to place the fences at least four times the trace to groundplane distance away from the line being ...
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Poker: Texas Hold'em (No Limit) Play two face down cards and the five community cards. Bet any amount or go all-in. By Masque Publishing