en:antennas
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en:antennas [2019/04/13 14:38] – fluktuacia | en:antennas [2019/07/13 12:26] – [Preamplifier LNA01A] 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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{{: | {{: | ||
+ | It represents a basic antenna, currently used on most of our stations. It has an advantage of having a 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. | ||
- | It represents | + | 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, |
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+ | [[en: | ||
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+ | ===== Helices - QHA ===== | ||
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+ | SC-QHA Helix is a type of circularly polarised antenna whose parameters can be almost homogenous over the whole hemisphere. The antenna | ||
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+ | {{: | ||
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+ | Bolidozor network would make use of a Helix design with a square ground area measuring 2x2m. Such constructions | ||
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+ | [[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 an observation site. Symmetric shape of its radiation pattern is also suitable for phase antennae fields, where there is necessary to optimise the sensitivity of antennae system for a specific type of observation. | ||
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+ | The following photos show the first build functional sample of a new patch antenna. | ||
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+ | {{ : | ||
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+ | {{ : | ||
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+ | === Parameters === | ||
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+ | The functional sample underwent a measurement of reflection using a Return Loss Bridge method. | ||
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+ | {{: | ||
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+ | * A way how to place a preamplifier is not solved | ||
+ | * The constructions is difficult to be implemented (e.g. it involves evening out a coiled mesh) | ||
+ | * It is not mechanically stable | ||
+ | * A way how to tune the antenna is not yet resolved | ||
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+ | Patch type antennae with a circular polarisation are difficult to manufacture, | ||
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===== Other types of antennas ===== | ===== Other types of antennas ===== | ||
- | An interesting antenna design, that should solve the drawbacks of GP antennas is so-called [[http:// | + | An interesting antenna design, that should solve the drawbacks of GP antennas is a so-called [[http:// |
- | A pair of crossed dipoles above a conducting plane could also result in interesting experimental solutions as it would be probably possible to integrate | + | A pair of crossed dipoles above a conducting plane could also result in interesting experimental solutions as it would be probably possible to integrate |
- | [[http:// | + | [[http:// |
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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:// | + | [[http:// |
{{cs: | {{cs: | ||
{{cs: | {{cs: | ||
+ | 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:// |
+ | * [[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