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en:antennas [2019/04/17 12:18]
fluktuacia
en:antennas [2019/04/21 14:58] (current)
fluktuacia [Modelling tools]
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 ====== Antennas for Bolidozor network ====== ====== Antennas for Bolidozor network ======
  
-Antenna is the first signal input to a [[en:​rmds|radio detection ​sattion]]. It is therefore necessary not to neglect its choice as a signal that is not received cannot be processed. A typical radio antenna receives not only meteor reflections,​ but also other radio signals - thus, the location of antenna is of high importance and should be chosen carefully. Suitable antenna characteristics can make the choice of location easier and can improve the overall antenna gain. Advantageous are following parameters: ​+Antenna is the first signal input to a [[en:​rmds|radio detection ​station]]. It is therefore necessary not to neglect its choice as a signal that is not received cannot be processed. A typical radio antenna receives not only meteor reflections,​ but also other radio signals - thus, the location of antenna is of high importance and should be chosen carefully. Suitable antenna characteristics can make the choice of location easier and can improve the overall antenna gain. Advantageous are the following parameters: ​
  
-  * Sensitivity in the upper hemisphere with respect to observation site. +  * Sensitivity in the upper hemisphere with respect to an observation site. 
   * High efficiency.   * High efficiency.
   * Insensitivity to signal linear polarisation angle.   * Insensitivity to signal linear polarisation angle.
-  * Suppression of unwanted ​signals ​reception from vely low elevations (usually ground noise).+  * Suppression of unwanted ​signal ​reception from very low elevations (usually ground noise).
  
  
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 {{:​cs:​antennas:​bolidozor_gp_antenna_mount.jpg?​600|}} {{:​cs:​antennas:​bolidozor_gp_antenna_mount.jpg?​600|}}
  
-It represents ​the basic antenna, currently used on most of our stations. It has an advantage of having small size and it is thus not difficult to install it on balcony, terrace, etc. Equally important is its relatively primitive design which allows for an easy construction suitable for beginners.+It represents ​basic antenna, currently used on most of our stations. It has an advantage of having ​small size and it is thus not difficult to be installed ​on balcony, terrace, etc. Equally important is its relatively primitive design which allows for an easy construction suitable for beginners.
  
-A disadvantage is a low gain and a radiation characteristic that has a sharp zero in zenith (meaning a very bad detection of meteors flying over the observation site, causing, subjectively,​ a big difference compared to visual observation). ​+A disadvantage is a low gain and a radiation characteristic that has a sharp zero in zenith (meaning a very bad detection of meteors flying over an observation site, causing, subjectively,​ a big difference compared to visual observation). ​
  
 [[en:​gpant|A more detailed description]]. [[en:​gpant|A more detailed description]].
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 ===== Patch antenna with a circular polarisation ===== ===== 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. ​+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 an observation site. Symmetric shape of its 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. The following photos show the first build functional sample of a new patch antenna.
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 +The functional sample underwent a measurement ​
 Na funkčním vzorku bylo měřeno přizpůsobení můstkovou metodou. (??) Na funkčním vzorku bylo měřeno přizpůsobení můstkovou metodou. (??)
  
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   * A way how to place a preamplifier is not solved   * 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)+  * The constructions is difficult to be implemented (e.g. it involves evening ​out a coiled mesh)
   * It is not mechanically stable   * It is not mechanically stable
   * A way how to tune the antenna is not yet resolved   * 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.+Patch type antennae with a circular polarisation are difficult to manufacture,​ because for their functionthey 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 type of antenna ​is therefore apparently overcome by SC-QHA antenna type.
  
 ===== Other types of antennas ===== ===== Other types of antennas =====
  
-An interesting antenna design, that should solve the drawbacks of GP antennas is so-called [[http://​on6wg.pagesperso-orange.fr/​Doc/​Antenne%20Eggbeater-Engl-Part1-Full.pdf|eggbeater]] or an antenna of [[http://​en.wikipedia.org/​wiki/​Turnstile_antenna|Turn style]] type.+An interesting antenna design, that should solve the drawbacks of GP antennas is so-called [[http://​on6wg.pagesperso-orange.fr/​Doc/​Antenne%20Eggbeater-Engl-Part1-Full.pdf|eggbeater]] or an antenna of [[http://​en.wikipedia.org/​wiki/​Turnstile_antenna|Turn style]] type.
  
-A pair of crossed dipoles above a conducting plane could also result in interesting experimental solutions as it would be probably possible to integrate ​the amplifier directly into the antenna. The resulting active antenna would have better noise parameters and reliability compared to design with separated GP antenna and LNA.+A pair of crossed dipoles above a conducting plane could also result in interesting experimental solutions as it would be probably possible to integrate ​an amplifier directly into an antenna. The resulting active antenna would have better noise parameters and reliability compared to design with separated GP antenna and an LNA.
  
-[[http://​en.wikipedia.org/​wiki/​Discone_antenna|Discone antena]] has also be tested for receiving the reflected signal. Although it works, it has an disadvantage of high bandwidth, that causes a penetrations of undesirable signals.+[[http://​en.wikipedia.org/​wiki/​Discone_antenna|Discone antena]] has also been tested for receiving the reflected signal. Although it works, it has an disadvantage of wide bandwidth, that causes a penetrations of undesirable signals.
  
  
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 ==== Preamplifier LNA01A ==== ==== 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 losses 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'​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’lead (?? svod antény) and a 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_plast16.jpg?​direct&​300 | }}
 {{cs:​antennas:​gp_plast17.jpg?​direct&​300 | }} {{cs:​antennas:​gp_plast17.jpg?​direct&​300 | }}
  
 +Preamplifier is therefore always installed in an immediate proximity of antenna in a 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 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. 
en/antennas.1555503534.txt.gz · Last modified: 2019/04/17 12:18 by fluktuacia