WiMo Crossed Yagis 432 MHz (70 cm, UHF)

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Top Features

  • Transmitting power max. 800 W
  • N-sockets
  • Robust construction

Supply Scope

  • boom tube, elements, dipoles
  • screw bag, mounting material
  • mast clamp
  • Mounting instructions

Technical description

What is a cross yagi?

A cross yagi consists of two normal yagi systems mounted on the same boom and rotated 90° in position.
The antenna (except the WX-208 with square boom) can be arranged on the mast so that the two systems are at 45° to the ground (X setup) or at 0°/90° to the ground (+ setup). With '+ setup' the mast must be made of non-conductive material, otherwise it would have a strong negative influence on the diagram of the vertical antenna.

Features of the WiMo Yagis

  • Highest possible gain with high bandwidth and good side lobe and return loss. Thus the antennas are oriented to the requirements of serious VHF amateurs, who need a high performance antenna for long distance traffic and all modes of operation. The design principles of the Yagis were worked out with computer programs calibrated at NEC and verified by many test setups.

  • Design current optimized
    Within a yagi structure, element currents should be uniform from the excitation center to the end of the antenna, not dropping too sharply. The yagis were designed for an optimal current profile. In older designs, there are jumps in the element current assignment, resulting in underutilized gain and poorer side lobe and return loss.

  • Minimum number of elements
    Other Yagis of comparable length have 2-3 elements more and thus more losses. Note: Antenna gain depends first of all on the antenna length, not on the number of elements!

  • Broadband elements
    Only good conducting aluminum tubes with 8 mm diameter are used for the elements. This represents the best compromise between minimum losses and the resulting wind load. Thin steel elements cause considerable additional ohmic losses and the skin effect, which is already very effective in VHF. Yagis with such elements give away more than 0.5 dB gain due to poor conductivity!

  • Defined element mounting
    Long-term stable with UV-resistant polyamide clamps. This means that there is no change in the electrical data even after years.
    If the elements would be fixed directly on the boom by metallic clamps, the effective element lengths and thus the antenna data could change insidiously by oxidation in the course of time!

  • Encapsulated dipole baluns
    The dipoles are real folded dipoles with Teflon baluns in the dipole box. So no forced matching with the known cladding wave problems! The connection is also made with the 70 cm antennas via an N-socket. The dipole boxes are absolutely weatherproof cold-welded and additionally foamed. The Teflonbalun is completely inside the dipole boxes. There is no balun loop that protrudes out of the junction boxes into the antenna and is then usually taped to the antenna more or less well! As a result, there are also no leakage problems at the twice pass of the balun loop through the dipole box.

  • Robust construction
    Except for the mast clamp itself, only screws, nuts and washers made of stainless steel (V2A) are used to ensure a long service life of the antennas. The element holders are made of UV-resistant polyamide, for the cross yagis with round tube boom they are made of aluminum.

  • German manual
    The manual contains all technical data and also information about sticking and interconnection of several identical antennas.

Application description

What is the purpose of crossyagis?

Crossyagis are mainly used for EME (Earth-Moon-Earth) connections, or for satellite connections. These are both modes that cross the ionosphere, where unpredictable polarization rotations often occur. To compensate for these and thus suffer less loss, circular polarization is used.

Of course, a cross yagi can also be used as a dual system with a vertical and a horizontal yagi, e.g. for wide area communication via FM relay (vertical) or via SSB direct links (horizontal).

How do I feed a crossagi?

Either both systems (both dipoles) are driven by one signal, but with different phasing, this way a circular polarization is achieved. For this purpose the X-position of the antenna is usually chosen. Or you switch a cable between both systems, then you have two antennas with + setup: a horizontal and a vertical Yagi. Of course it would be also conceivable to lay two cables to use both systems at the same time, or to switch only in the shack.

If one wants to have only a fixed, not switchable circular polarization, then cables of different length are sufficient, which are united over a 3dB coupler (splitter) on a cable.

If one wants to have the maximum flexibility, one can mount a polarization remote switch (see accessories) on the antenna. From this box, two cables go to the antenna, one coax and one control cable to the radio. The remote switch then provides the ability to switch between left or right hand circular polarization, or between horizontal or vertical linear polarization.

We offer the UHF crossyagis in 2 variants:

  • WX-7020: The shorter version has a boom with a length of 2 meters and 2 x 10 elements.

  • WX-7036: The long version has 2 x 18 elements, the boom is 3.40 meters long.
Technical Data
Product Name WiMo Crossed Yagis 432 MHz (70 cm, UHF)
Antenna Type Directional Antenna
Design of antenna Crossed Yagi
Antenna Guying No
Band 70cm
Brand WiMo
Frequency Range 430 - 440 MHz
Front/Back ratio [dB] > 20
Max. Power [W] 800 W
Polarisation Circular or Linear
Balun Included Yes
Strut no
Max. Windspeed (km/h) 120

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