4/28/2021 0 Comments 2.4Ghz Transmitter
If the wire is vertical the polarization is also vertical, if horizontal the polarization is horizontal and everywhere in between it follows the wire orientation.For RC this isnt as easy as analyzing a simple point-to-point fixed link since there is a continually changing geometric relationship between the transmitter and receiver.
This can account for a lot of the momentary control glitches we sometime see with typical antennas. Some other factors that also affect the link integrity are interference from other users of the spectrum as well as interference we generate ourselves by reflections of our own signal from surrounding objects. The choice of antennas used on both the transmitter and receiver can have a significant bearing on these issues and link range. The antennas supplied by OEMs with their radio systems are usually far from optimum for the task at hand and are made to a price meaning cheap. Two antenna characteristics, among others, that impact link performance to a large degree are directivity and polarization. Some people tend to confuse the two but its important to sort it out. Another factor thats often quoted (mostly to sell after-market antennas) is gain. Antenna gain can be a useful number if understood in the right context. Gain is a product of antenna directivity and to be meaningful, requires a reference antenna for comparison, which is most commonly an isotropic radiator. This is a hypothetical antenna that radiates (or receives) equally well in all directions i.e., it is an antenna where the radiation pattern is a sphere with the antenna located at the center. Units for gain using this reference are dbi, meaning decibels improvement (or loss -dbi) compared to the isotropic reference. A simple dipole antenna has a gain of 2.15 dbi and has a directivity pattern, in free space, shaped like a torus or donut. Since the radiation is much less in the hole of the donut, it holds that it has to be greater in some other directions. Thus, the dipole has gain in its favored directions compared to isotropic. ![]() ![]() This is why we are told to not point the antenna at the plane. Do we always do this while concentrating on flying I doubt it. Linear antennas with higher gain (2dbi) need to be used with caution. The directivity pattern often has multiple narrow lobes with nulls between. This results in more signal fading as the planetransmitter orientation changes and monitoring the transmitter position in your hands becomes necessary. If more antenna gain is needed to extend range, there are antenna types with increased gain without breaking up the pattern into narrow lobes but youre not going to find them at your favorite RC supplier. Antenna polarization is the orientation of the electric field component of the transmitted radiation and for simple linear antennas, is the same as the orientation of the antenna conductor (wire).
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