Last Revision: 1 April 2008
This is a new own design for 2 * 11 element antennas for 432 MHz. It is derived from a design by Rainer Bertelsmeier DJ9BV (20 BVO). I cut it down to 11 elements and have a length of about 1.90m overall for the antenna. Furthermore I made some small adjustments to the element lengths due to different diameters of the elements to the original design. A DK7ZB design would give a few tenths of a dB additionally; I wanted to use available equipment like the folded dipole.
The stacked antenna (two of those) will have a gain of about 17.2 dBi, which is a real good value.
The antenna has a folded dipole (Available from Konni-Antennen) including a balun transformer. The size boom is 20*20mm square tube with 2mm wall. The elements have a diameter of 6mm and they are mounted ca 6mm above the boom by polyamid holders. The antenna is end supported, so no mast tube will pass through the antenna and disturb the field.
EZNEC wires listing. All dimensions are in Millimeters
Design view of the antenna.
VSWR of the 11 element antenna for 432 MHz
For increasing the gain I intend to stack the antenna. Gain raises by ca 2.5 dB by a stacking distance of 900 mm. Doing more will give slightly more gain, but side lobes will increase to "unuseful" values.
Vertical diagram of the two antenna stack.