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The vertical DK7ZB-Duoband-Dipole for 2m/70cm
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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. The choke has 5 turns of RG174 on 25 mm. Position of the elements are measured from center of element to outer side of the mast. |
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Element
(10mm) |
Position |
Length |
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2m-Dipole |
280mm |
936mm (tip
to tip) |
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70cm-open-sleeve-element |
307mm |
316mm |
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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.
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Element |
Position |
Length |
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70cm-Reflector |
150mm |
324mm |
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2m-Dipole |
280mm |
936mm (tip
to tip) |
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70cm-open-sleeve-element |
309mm |
313mm |
