|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 Construction Principles for Duoband-Yagis 2 m/70 cm
An interesting phenomenon is the 3/2-lambda resonance of 2-m-elements on the 70-cm-band.
A dipole for 2m has a very interesting azimuth pattern on 70cm.
0 dB = 0,85 dBd
|Now we add the 70-cm-open-sleeve-element to the 2-m-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 70 cm with 50 +/- j 0 Ohm.|
Pattern of this construction
0 dB = 4,63 dBd
We can use this open-sleeve-construction as the radiating system in a Yagi for two bands.