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An interesting phenomenon is the 3/2-lambda resonance of 2m-elements on the 70cm band. A dipole for 2m has a very interesting azimuth pattern on 70cm. 0dB = 0,85dBd |
| Open-sleeve principles | VHF-Duoband principles | 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 Construction Principles for Duoband-Yagis 2m/70cm
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An interesting phenomenon is the 3/2-lambda resonance of 2m-elements on the 70cm band. A dipole for 2m has a very interesting azimuth pattern on 70cm. 0dB = 0,85dBd |
Now we add the 70cm-open-sleeve-element to the 2m-dipole. The currents change and we have the highest current in the parasitic fed open-sleeve element. With the correct distance we get one feedpoint for two bands, on 70cm with 50 +/- j 0 Ohm.
Pattern of this construction 0dB = 4,63dBd |
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Now we can use this open-sleeve-construction as the radiating system in a Yagi for two bands.