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Small receiving loops are sized at 1 / 4 ~ 1 / 10 wave perimeters, sometimes with many turns of wire around the same supporting frame. Small loops are widely used as compact direction finding antennas, since their "null" direction is exceptionally precise, and their small size makes them much more compact as hand-carried ...
[3] [4] The gain will be somewhat lower than a dipole, or a quarter-wave whip with an adequate size ground plane. Whips not mounted on the radio itself are usually fed with coaxial cable feedline of 50 ohm or 75 ohm impedance. In transmitting antennas the impedance of the antenna must be matched to the feedline for maximum power transfer.
A Yagi–Uda antenna, or simply Yagi antenna, is a directional antenna consisting of two or more parallel resonant antenna elements in an end-fire array; [1] these elements are most often metal rods (or discs) acting as half-wave dipoles. [2]
For example, the SWR bandwidth is typically determined by measuring the frequency range where the SWR is less than 2:1 . Another frequently used value for determining bandwidth for resonant antennas is the −3 dB return loss value, since loss due to SWR is −10·log 10 (2÷1) = −3.01000 dB.
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 9.7 dBi can be achieved at 28 MHz. [3] Because the placement and size of the parasitic reflector both depend highly on wavelength, each Moxon antenna functions properly on the frequency band ...
Patch antenna gain pattern. A directional antenna or beam antenna is an antenna which radiates or receives greater radio wave power in specific directions. Directional antennas can radiate radio waves in beams, when greater concentration of radiation in a certain direction is desired, or in receiving antennas receive radio waves from one specific direction only.