HB9CV
La antena direccional HB9CV-Beam de 2 elementos alimentados fue presentada por Rudolf Baumgartner ( HB9CV ), en la década de 1950.
The Beam is a coax-fed version of the ZL-Special. The reflector is fed 225° out of phase. The distance between the two elements is 1/8-Lambda (45°), with the two crossed phase lines of 180° results the 225°.
It is astonishing that this antenna is not well known in many countries, the ARRL-Antenna-Book does not mention this type of antenna.
You will get the beam very easy to work, because the influence of the element-diameters is much less critical than by parasitic Yagis, where the tapering and the element diameters are very important for the mechanical length of the elements. The gain is in the range of 4,1-4,2dBd.The HB9CV has a great bandwidth and a very good F/B, which are more dependent on the phase shift and the two driven elements than on the physical lengths of the elements and their individual dimension. The mechanical construction is a little bit difficult for the phasing lines and you need a compensation-C for tuning the SWR. For tuning use a variable capacitor (max. C see below), tune for best SWR (<1,2) and use then a fixed capacitor with the same value.
The 50MHz-HB9CV
Boom 25x25mm square-Aluminium
Elements 12x1mm round Aluminium
Lengths in mm
From the coax-socket goes a capacitor to the point X, here 15pF (try out for best SWR) The phasing line is made of 2mm brass wire and has a distance of 5mm to the elements (uncritical).
The picture shows the construction of a 2m- HB9CV-Beam better than a long description.
Here you see the details of the 2m-HB9CV with the point X, the C=15pF and the coax socket. The phasing line is fixed with 5mm distance to the boom.
