Differences

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--- en:antennas [2019/04/14 13:13] – [Helixes - QHA] fluktuacia
+++ en:antennas [2019/04/18 14:39] – fluktuacia
@@ Line 33: / Line 33: @@
 [[en:qha|A more detailed description]].
+===== Patch antenna with a circular polarisation =====
+This antenna was designed to improve the gain of the receiving system compared to a currently used GroundPlane antenna. Patch antenna does not have the zero in zenith and has an almost hemispherical radiation characteristics - that is why it is also sensitive to signals from objects flying directly over the observation site. Symmetric shape of radiation pattern (?? vyzařovací charakteristika) is also suitable for phase antennae fields, where there is necessary to optimise the sensitivity of antennae system for a specific type of observation.
+The following photos show the first build functional sample of a new patch antenna.
+{{ :cs:antennas:bolidozor_patch_antenna1.jpg?500 |}}
+{{ :cs:antennas:bolidozor_patch_antenna2.jpg?500 |}}
+=== Parameters ===
+Na funkčním vzorku bylo měřeno přizpůsobení můstkovou metodou. (??)
+{{:cs:antennas:patchant_freq_char.png?200|}}
+  * A way how to place a preamplifier is not solved
+  * The constructions is difficult to be implemented (e.g. it needs to even out a coiled mesh)
+  * It is not mechanically stable
+  * A way how to tune the antenna is not yet resolved
+Patch type antennae with a circular polarisation are difficult to manufacture, because for their function they need a good tuning of the phase shift of two orthogonal linear polarisations - achieved by a deformation and a change in geometrical size of an antenna radiator. Thus it follows that it is easy to detune an antenna by a resonator deformation or a change in dielectric parameters of an environment between a radiator and a reflector. The construction of this antenna type is therefore apparently overcome by SC-QHA antenna type.
 ===== Other types of antennas =====
@@ Line 46: / Line 72: @@
 ==== Preamplifier LNA01A ====
-Good quality preamplifier is essential due to antenna's low gain and low intensities of reflected signal.
+A good quality preamplifier is essential due to loses during signal propagation via antenna and due to low intensities of reflected signal.
-[[http://www.mlab.cz/Modules/CommRF/LNA01A/LNA01A_Bottom_Small.JPG|LNA01A]] represents a preamplifier designed for meteor detection in 2m band. It amplifies the signal from antenna and thus decrease the effect of receiver's own noise. It further reduces complications connected with signal transmission via coaxial cable (it compensates for the cable attenuation and so it is possible to use cheaper coaxial cable of RG58 type).
+[[http://www.mlab.cz/Modules/CommRF/LNA01A/LNA01A_Bottom_Small.JPG|LNA01A]] is a preamplifier designed for meteor detection in 2m band. Its benefit is mainly in amplification of signal from antenna (thus decreasing the influence of antenna’s lead (?? svod antény) and the noise from receiver). Furthermore it reduces complications connected to signal radiation from receiver’s oscillator.
 {{cs:antennas:gp_plast16.jpg?direct&300 | }}
 {{cs:antennas:gp_plast17.jpg?direct&300 | }}
+Preamplifier is therefore always installed in the immediate proximity of antenna in an plastic waterproof wiring box.
-==== Further improvements ====
+==== Modelling tools ====
-Antenna should fulfil these requirements.
+  * [[http://www.qsl.net/kd2bd/splat.html|RF Signal Propagation, Loss, And Terrain analysis tool for the electromagnetic spectrum between 20 MHz and 20 GHz.]]
+  * [[http://en.wikipedia.org/wiki/Numerical_Electromagnetics_Code|NEC2 software]]
+  * [[https://github.com/BogdanDIA/nec2-array|Antenna field in v NEC2]]
-  * It should have larger gain than currently used Ground Plane.
-  * Radiation pattern should not reach zero at zenith.
-  * It should have hemispheric radiation pattern.
-  * It should be possible to integrate it with an amplifier.
-  * Radiation pattern and directionality should be made adjustable via phasing of more antennas.