Neil Smith G4DBN
Simulation is working fine, but I had a feeling there was an
analytical solution to calculate the characteristic impedance of a
dielectric rod waveguide in air. Intellectual curiosity getting
the better of me in late-night modelling sessions....
The extension rod does seem to reduce the sidelobes a little when it is about 6mm diameter. I'm more interested in getting the edge taper right, and by adjusting the cone angle, I can get a nicely flattened lobe with a slight dip in the middle. This is in a 22 mm diameter tube but with a narrower lobe and no dip. It will be amusing to see if the real thing is anything close to the models