en:antennas
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en:antennas [2014/08/01 18:23] – created fluktuacia | en:antennas [2019/07/13 12:20] – [Patch antenna with a circular polarisation] fluktuacia | ||
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+ | ====== Antennas for Bolidozor network ====== | ||
+ | |||
+ | Antenna is the first signal input to a [[en: | ||
+ | |||
+ | * Sensitivity in the upper hemisphere with respect to an observation site. | ||
+ | * High efficiency. | ||
+ | * Insensitivity to signal linear polarisation angle. | ||
+ | * Suppression of unwanted signal reception from very low elevations (usually ground noise). | ||
- | ====== Antennas for receiving signals reflected from meteors ====== | ||
===== Plastic 1/4 lambda GroundPlane ===== | ===== Plastic 1/4 lambda GroundPlane ===== | ||
- | 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 designs which allows for easy construction suitable for beginners. | + | {{: |
- | + | ||
- | Disadvantage, | + | |
- | [[http://www.ccars.org/ | + | {{:cs: |
- | Antenna socket connector is [[http:// | + | 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. |
- | antenna plug is [[http:// | + | |
- | {{cs: | + | 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, |
- | {{cs:antennas: | + | [[en:gpant|A more detailed description]]. |
- | {{cs: | ||
- | {{cs: | + | ===== Helices - QHA ===== |
- | {{cs: | + | 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. |
- | {{cs: | + | {{:cs: |
- | {{cs: | + | 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. |
- | {{cs:antennas: | + | [[en:qha|A more detailed description]]. |
+ | |||
+ | ===== Patch antenna with a circular polarisation ===== | ||
- | {{cs: | + | 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. |
- | {{cs: | + | The following photos show the first build functional sample of a new patch antenna. |
- | {{cs: | + | {{ :cs: |
- | {{cs: | + | {{ :cs: |
- | The total length of 143MHz active element is 499mm and the length of short circuited stub from RG213 is 346mm. | + | === Parameters === |
- | ==== Antenna location ==== | ||
+ | The functional sample underwent a measurement | ||
+ | Na funkčním vzorku bylo měřeno přizpůsobení můstkovou metodou. (??) | ||
- | Active element should be placed far enough (at least 2 lambda) from any large or conductive objects such as walls of buildings, wires, railing etc. | + | {{: |
- | The most suitable direction of antenna | + | |
+ | * 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 | ||
+ | |||
+ | |||
+ | Patch type antennae with a circular polarisation are difficult | ||
===== 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. | + | |
- | * It should have larger gain than currently used Ground Plane. | + | * [[http:// |
- | * Radiation pattern should not reach zero at zenith. | + | * [[http://en.wikipedia.org/ |
- | * It should have hemispheric radiation pattern. | + | * [[https:// |
- | * 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