OPTIBEAM OB6-3M, Руководство пользователя, Страница: 6 / 12

5
1. Introduction
The OB6-3M is a high performing Triband Antenna for the 14, 21 and 28 MHz amateur radio bands
which, by use of a tuner, can also be used on the 18 and 24 MHz WARC bands as a compromize.
OptiBeam shortwave antennas are designed and optimized by support of modern techniques such as
computerized antenna simulation and are finally adjusted by extensive tests in practice.
The core of the antenna consists of a direct coupled 3-element-drivercell, where the drivers are
connected with a phase line of square tubes. There is a separate reflector for the 20m and the15m
band and a separate director for the 10m band.
A specialty are the 20m elements which are bent, following the Moxon rectangular technique.
Hereby the size of the antenna is reduced considerably without sacrifying any efficiency while the f/b
ratio is increased simultaneously.
By this new concept of feeding in combination with a special order of all elements and the exclusive
use of full size elements (also valid for the bent 20m elements) highest efficiency, optimum bandwidth
concerning high gain, clear pattern and low SWR together with unlimited power handling are achieved.
In the following table the essential electrical and mechanical data can be seen:
Bands 20m / 15m / 10m *
Gain (dbd)** 4,2 / 4,1 / 4,7
Gain (dbi)*** 11,5 / 11,8 / 12,5
F/B (db) 25 / 15 / 25
SWR:
14,00 - 14,19 - 14,35
21,00 - 21,25 - 21,45
28,00 - 28,50 - 29,00
1,3 - 1,0 – 1,3
1,8 - 1,1 – 1,7
1,2 - 1,1 – 1,3
Impedance (Ohm) 50
Elements 6
Active elements 20/15/10 2 / 2 / 2
Max. element length (m) 8,08
Boom length (m) 3,10
Weight (kg) 15
* = with a tuner as a compromize also usable on 17/12m
** = average gain over a dipole in free space
gain of monobanders for comparison: 2-element Yagi: 4 dbd, 3-element Yagi: 5-6 dbd
*** = average gain at 20m above ground
2. Assembly
The included schematic diagram is needed for the assembly and the following information is given:
-> type of element (R=Reflector, S=Driver, D = Director) and the position on the boom
-> measurements of the element sections (length and diameter)
-> lengths of the element halves
-> distances between the elements.
The lengths are given in m (meters) and the diameters are given in mm (millimeters).
2.1 Sorting the parts
The antenna partly consists of already pre assembled parts.
All parts of the antenna are marked.
For faster and easier assembly it is recommended to sort the parts per band.