| Open-sleeve principles | VHF-Duoband principles | Duoband-Yagi 6m/10m | 10m-Dipole+ 3-El.- 6 m | Triband-Yagi 6m/4m/2m | Duoband-Dipol 2m/70cm | 2m/70cm 2+2/3 El. | 2m/70cm 4+5 El. | 2m/70cm 5+8 El. |
The vertical DK7ZB-Duoband-Dipole for 2m/70cm
 |
This dipole for 2m with an open-sleeve- element for 70 cm must be mounted in front of a mast. Otherwise the feedpoint impedance for 2 m is 72 Ohm and not 50 Ohm. The mast acts as a reflector. Gain on 2 m is 2,6 dBd and on 70 cm is 4,6 dBd. The elements are made of 10x1 mm aluminium tubes. Do not use other diameters! The radiator has a length of 936 mm from tip to tip with 10 mm spacing. Position of the elements are measured from center of element to outer side of the mast. |
 |
 |
|
Element
(10mm) |
Position |
Length |
|
2m-Dipole |
280mm |
936mm (tip
to tip) |
|
70cm-open-sleeve-element |
307mm |
316mm |
 |
For a better pattern on 70 cm we should add a 70-cm-reflector. So we come to a vertical polarized 2-Element-Yagi for 70 cm. The gain increases to 5,4 dBd on 70 cm, on 2 m we have no changes. The 70-cm-open-sleeve-element must get a new length and an other position.
|
|
Element |
Position |
Length |
|
70cm-Reflector |
150mm |
324mm |
|
2m-Dipole |
280mm |
936mm (tip
to tip) |
|
70cm-open-sleeve-element |
309mm |
313mm |
