Search results
Results from the WOW.Com Content Network
The G5RV antenna is a dipole with a symmetric resonant [1] feeder line, which serves as impedance matcher for a 50 Ω coax cable to the transceiver. [ 2 ] [ 3 ] Origin
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
SWR (standing wave ratio) is typically 1.5:1 or less over several octaves of frequency. [4] A discone antenna consists of three main parts: the disc , the cone , and the insulator . The disc : The disc should have an overall diameter of 0.7 times a quarter wavelength of the antenna's lowest frequency .
For example, a certain antenna used well away from its resonant frequency may have an SWR of 6:1. For a frequency of 3.5 MHz, with that antenna fed through 75 meters of RG-8A coax, the loss due to standing waves would be 2.2 dB. However the same 6:1 mismatch through 75 meters of RG-8A coax would incur 10.8 dB of loss at 146 MHz.
Pyramidal horn antennas for a variety of frequencies. They have flanges at the top to attach to standard waveguides. A horn antenna is used to transmit radio waves from a waveguide (a metal pipe used to carry radio waves) out into space, or collect radio waves into a waveguide for reception.
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.
[1]: 27‑21 The meter or amplifier (not shown) connected to the FWD and REV terminals acts as the required drain resistor, and determines the dwell-time of the meter reading. Interior view of an SWR meter. The three parallel coupled lines are visible. Diodes, capacitors and termination resistors are mounted at the ends of the sense lines.
Due to their omnidirectional radiation pattern, vertical monopole antennas are commonly used in terrestrial radio communication systems in which the direction to the transmitter or receiver is unknown or constantly changing, [7] such as broadcasting, mobile two-way radios, and wireless devices like cellphones and Wi-fi networks, [8] [4] because they radiate equal radio power in all horizontal ...