Quad antenna
As a quad antenna ( also quad or Cubical Quad ) is called full wave loops ( wire length = wavelength), preferably in a square shape. It may consist of one or more cascaded and fed only elements ( lamps). In addition, one or more parasitic elements ( directors and reflectors) can increase the directivity and the associated antenna gain.
Construction
The elements can also form a rhombus or a circle. In this case, the larger is the framed by the full wave loop area, the higher the directivity and the antenna gain. For technical reasons, however, are usually square shapes are used.
The early Quad antennas were built of bamboo material which has been preserved with alkyd resin. Thus, they were useful for years. The modern quad antennas consist of GRP pipes, Ramin, epoxy pipes, as well as special quad center pieces from Aluspritzguss.
Properties
If the quad powered down, the polarization is horizontal, vertical in lateral infeed. She has a stronger vertical focusing compared to a Einzeldipol and has a horizontal eight characteristics. When using directors and reflectors ( at short wavelengths, often a metal or grating surface ) as well as several emitters (two or more phase-shifted powered quad antennas in a row) the directional pattern is changing towards a mace. The additional ( active or parasitic ) elements the quad antenna achieved in the tuned frequency range a relatively high antenna gain and greater directivity.
While fed loops must have a circumference which corresponds to a wavelength, the amount of the directors of the periphery of the reflector is slightly shorter and slightly longer. Driven element, reflector and directors are not electrically coupled, but can be mounted on a common support bar ( boom ). The exact lengths are influenced by the environmental conditions, therefore usually a vote (eg by means of so-called stubs ) at the installation is necessary.
The size and the power supply affect the polarization. A distinction is made horizontal and vertical polarization; Special forms such as X - quad allow circular polarization.
The quad antenna is a very quiet antenna because of their electrically closed structure. It receives less interference than open antenna shapes, such as the typical crackling with static charged rain or snow is at least considerably lower. Also in the case of transmission, it significantly reduced or interference with electronic devices in the neighborhood, which often show up because of technical and constructive shortcomings of this vulnerable. Also mounted in relatively low height, it is considered good flat radiator and is therefore particularly suitable for long distance connections (DX).
The disadvantage is that at low frequencies very expansive constructions are necessary.
History
This type of antenna has been high in the Andean jungle near Quito in Ecuador for the operated since 1938 radio station Radio HCJB, Clarence C. Moore ( W9LZX ) in 1942 one of the station engineers and amateur radio developed. The reason for this was that in 3000 m altitude, the air so strongly ionized that the element ends of the 4-element directional light initially used melted away by corona discharge ( St. Elmo's Fire ). To avoid this, he searched a closed antenna design. In this way, finally resulted in the first Cubical Quad.
The first release made Clarence C. Moore in 1947, when he returned to the United States, the quad antenna filed for a patent and this was 1951.
Bi-quad antenna
Recently, the antennas are used in the form of bi- quads in the wireless technology and wardriving scene. Here they are usually removed with a metal plate as a reflector for directional antenna. The bi- quad has a base resistance of about 60 Ω, which allows connection to coaxial cable, with the shield of the cable is connected to the reflector. This also the unbalanced coaxial cable is adapted to the symmetric radiator and there are no standing waves. A horizontally lying "8" here has a vertical polarization.
Application
Quad antennas found and are widely used in professional radio services, the military and the external services. The typical frequency spectrum ranges from the short wavelength into the gigahertz range
Even in the amateur radio service Quad antennas are appreciated for decades and proven particularly useful as DX antenna ( wide connection). Due to the presence of the radio amateurs extensive experience and literature on this type of antenna they used by radio amateurs mostly self built and developed until today. The materials for this purpose come from the hardware store, dragon flying, amateur radio, and natural products.
There are a large variety of types of quad antennas, including: dual Quad (also Bi - Quad), X - Quad Cubical Quad, Bird Cage, Swiss Quad, German Quad, UA3IAR quad, multi-band cubical quad, tri-band quad, five-band quad, Mini Quad, Mini Quad G3YDX, Spider- Quad, Quad - DJ4VM and more.