FAQ

What is the advantage of parabolic antennas?
Parabolic antenna is the most efficient type of a directional antenna – large front/back ratio, sharp radiation angle and small side lobes. It fits well for noisy locations where other antennas factually do not work.

The antenna's Gain is adequate to the area of the reflector. The reflector can be central-focused (the focus is in the centre of the dish) or offset (the focus is off the axis of the dish). WAVEANT manufactures only centre-focused dishes because they can be easily directed and have better mechanical characteristics.

The next advantage is the easy assembly of the plastic cover kit (RADOM) and collar, which is hardly possible with offset dishes. The plastic cover kit eliminates the hoarfrost and layers of snow, the collar increases the possibility of directing the antenna and suppresses undesirable jamming.

Various types of radiators can be used for radiating the reflector. WAVEANT uses a so-called opened wave-guide, which is a hollow cylinder with exact dimensions typical for every frequency and width of the working band. In addition, we add other compensation elements into the wave-guide, which adjust a radiation angle (120° is a standard) and improve the antenna adjustment (SWR). A great advantage of the opened wave-guide is its high front/back ratio and sharp course of directional radiating characteristics.

Warning! The antenna designed for the frequency band 5 GHz will hardly work if connected to a device transmitting on the frequency band 2,4 GHz and vice versa!
What is the advantage of parabolic antennas for the frequency band 2.4 GHz?
In general, they serve for connection of end users (so-called last mile) to a wireless network. However, in areas with lower intensity of WiFi networks, they can be successfully used also for back-bone links. In fact, this frequency is used for connections up to maximum 10 km.

  • Grids: they are designed for less demanding installations, they are wind resistant, but have worse parameters than full dishes.
  • Dishes: they have a sharp radiating lobe, large front/back ratio and they are designed for demanding installation (wind!)
What is the advantage of parabolic antennas for frequency 5 GHz?
In general, they serve for building spinal point-to-point connections. The jamming in this band is lower than in the frequency band 2.4 GHz and, thanks to large directionality, it is possible to use more directional connections in the same frequency in the same locality. In recent time, low-size dishes are used to connect end customers requiring high quality and reliability of connection
  • Grids: due to short waves, manufacturers do not use them for this frequency, front/back ratio is insufficient.
  • Dishes: the only possible solution for the frequency band 5 GHz and more.
What the „SWR Course (standing wave ratio)” is?
SWR is the main indicator of the antenna's quality. Usually, SWR is defined as the ratio of the maximum radio-frequency (RF) voltage to the minimum RF voltage along the line. The lower the curve is, the better. The ideal state (hardly to be factually achieved) would be if the SWR equalled to one (it happens only in laboratories with calibration resistance) within the whole working range of the antenna (independently on the frequency).

Průběh PSV
SWR Course with Waveant WA18-24

In practice, the antenna with the SWR lower than 1.5 is deemed an excellent antenna, the antenna with the SWR by 2.0 is considered suitable and SWR higher than 2.0 is considered the antenna substandard. The antenna with the SWR exceeding the value 3 is considered insufficient.
What does the „radiation chart” show?
The radiation angle shows the course of intensity of the electromagnetic field in a constant distance from the antenna depending on the angle of the dish axis. It is usually measured in two levels – horizontal and vertical. As regard to WAVEANT parabolic antennas, the radiation chart in the horizontal and vertical position is nearly the same. The curve of this course can be also called "equipotential".

Vyzařovací charakteristika WA 20-24
Radiation chart with the antenna Waveant WA18-24

The X-line shows the angle in degrees, Y-line shows the value of the measured signal in average units dB (decibel). The decibel is an equivalent of the percentage: 0 dB = 100%, -3 dB = 50%, -6 dB = 25%, etc.

It is impossible to express an ideal "radiation chart", because requirements differ for every type of use. With an omni-directional antenna, the ideal chart on the horizontal level will be the circle, with a directional antenna, the ideal chart will be the line going in the direction of the antenna's radiation (e.g. in the dish axis).
What is the „polarization”?
With wifi antennas, circle or linear polarization is most often used. In practice, linear polarization is used as horizontal and vertical. Circle polarization can be clockwise or anti-clockwise. The polarization level of the radiating wave motion depends exclusively on the construction of the antenna.
What is the „Gain of the antenna in dBi”?
No additional power is supplied into the antenna (only VF signal from the card or access point) and therefore the signal cannot be strengthened there (in absolute units). The antenna, which has a positive Gain, is always the antenna directional in some manner, i.e. it can direct its transmitting/receiving ability only to a certain direction, while other directions becomes "deaf". The Gain of the antenna then shows how many times a certain preferred direction of the antenna is given priority as compared to the situation, when the antenna behaves in the same manner in all directions (i.e. its radiation chart would be an ideal ball).

Also the omni-directional antenna has the Gain, it works as omni-directional only in one level and its radiation chart is a "cake" (more or less flat). Therefore the omni-directional antenna does not work well upwards (where we do not need it much), but neither downwards (where we could miss its operation).
Is the Conformity Declaration issued to Waveant antenna?
No, passive antennas are not considered a device which could meet the definition of the radio equipment. In fact it means, that the antennas are not labelled with the "CE" or other designation and no Conformity Declaration is attached.