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The balun is a 16:1 ratio, thereby transforming the 50 Ω (ohm) coax to an 800 Ω feed at the antenna. The resistor load is also 800 Ω , non-inductive. This allows the antenna impedance to swing from 400–1,600 Ω over the frequency range intended and thus keep the SWR at the transmitter 2:1 or lower.
For this reason, when attaching a twin-lead line to a coaxial cable connection, such as the 300 Ω twin-lead from a domestic television antenna to the television's 75 ohm coax antenna input, a balun with a 4:1 ratio is commonly used. Its purpose is double: First, it transforms twin-lead's 300 Ω impedance to match the 75 Ω coaxial cable ...
German physicist Heinrich Hertz first demonstrated the existence of radio waves in 1887 using what we now know as a dipole antenna (with capacitative end-loading). On the other hand, Guglielmo Marconi empirically found that he could just ground the transmitter (or one side of a transmission line, if used) dispensing with one half of the antenna, thus realizing the vertical or monopole antenna.
It is a two element Yagi-Uda antenna with folded dipole elements, and no director(s). Because of the folded ends, the element lengths are approximately 70% of the equivalent dipole length. The two-element design gives modest directivity (about 2.0 dB ) with a null towards the rear of the antenna, yielding a high front-to-back ratio : Gain up to ...
A transmatch (antenna tuner) is not required to use this antenna near its nominal design frequency of 14 MHz, and judicious length adjustments can sometimes include one other frequency band. All other frequencies require a transmatch. [citation needed] There are many variants of the G5RV antenna. Two variations of the G5RV design, called ZS6BKW ...
Generally the mutual coupling tends to lower the impedance of the primary radiator and thus, folded dipole antennas are frequently used because of their large radiation resistance, which is reduced to the typical 50 to 75 Ohm range by coupling with the passive elements. Two Yagi–Uda antennas on a single mast.
Yagi antenna for UHF TV reception with 22 parasitic elements; 4 reflectors attached to the vertical bracket at left, and 18 directors attached to the horizontal beam at right. The driven element is attached to the black box next to the reflectors. The antenna is most sensitive to radio waves coming from the right, parallel to the antenna's axis.
Likewise with CATV, although many broadcast TV installations and CATV headends use 300 Ω folded dipole antennas to receive off-the-air signals, 75 Ω coax makes a convenient 4:1 balun transformer for these as well as possessing low attenuation. The arithmetic mean between 30 Ω and 77 Ω is 53.5 Ω; the geometric mean is 48 Ω. The selection ...