en:antennas
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en:antennas [2019/04/13 16:23] – [Plastic 1/4 lambda GroundPlane] fluktuacia | en:antennas [2019/04/21 14:49] – [Antennas for Bolidozor network] fluktuacia | ||
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====== Antennas for Bolidozor network ====== | ====== Antennas for Bolidozor network ====== | ||
- | Antenna is the first signal input to a [[en: | + | Antenna is the first signal input to a [[en: |
- | * 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 | + | * Suppression of unwanted |
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[[en: | [[en: | ||
+ | |||
+ | ===== Helices - QHA ===== | ||
+ | |||
+ | SC-QHA Helix is a type of circularly polarised antenna whose parameters can be almost homogenous over the whole hemisphere. The antenna is tuned mainly by a proper phasing of its four powering points. | ||
+ | |||
+ | {{: | ||
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+ | Bolidozor network would make use of a Helix design with a square ground area measuring 2x2m. Such constructions has an advantage compared to a standard self-phase QHA antenna in that it has a narrower receiver bandwidth and greater total efficiency. | ||
+ | |||
+ | [[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. | ||
+ | |||
+ | {{ : | ||
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+ | {{ : | ||
+ | |||
+ | === Parameters === | ||
+ | |||
+ | |||
+ | Na funkčním vzorku bylo měřeno přizpůsobení můstkovou metodou. (??) | ||
+ | |||
+ | {{: | ||
+ | |||
+ | |||
+ | * 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, | ||
+ | |||
===== Other types of antennas ===== | ===== Other types of antennas ===== | ||
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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 loses during signal propagation via antenna and due to low intensities of reflected signal. |
- | [[http:// | + | [[http:// |
{{cs: | {{cs: | ||
{{cs: | {{cs: | ||
+ | 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:// |
+ | * [[http:// | ||
+ | * [[https:// | ||
- | * 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.txt · Last modified: 2019/07/13 12:27 by fluktuacia