Davemade groundplane / birdcage antenna

[HomerBB]

I did not build it.
I went looking for it. Yahoo mail did not keep the pdf.

 

[Marconi]

Does this mean I sent you the dimensions and details for this model? My model is dated 6/9/19.

 

[HomerBB]

@Marconi Here is what I've got. Dated 8-13-2012.

 

[Marconi]

Now we're on the same page Homer, and have something to look at.

What do these 2 models tell us about the Bird Cage antenna?

 

[HomerBB]

I suppose the obvious is the horizontal radials show more gain, but the upward slanted radials suppress the near vertical radiation.
I have to wonder what a longer vertical would do... perhaps add gain and slightly reposition the out of phase lower radiation more within the cone.
I think a ring around the top of the radials will contribute also by possibly causing the upturned radials to appear longer to RF.
Maybe...

All of these characteristics are already present on the birdcage antenna.
We have examined the V4k extensively. The idea behind my question with this model was whether upturned radials that were isolated from the vertical would contain the out of phase lower radiation and contribute to improved gain on a traditional 5/8.
I think it will but only when we lengthen the vertical. On the 5/8 upturned radials leave only 3/8 wavelength vertical above the cone.
It can be seen that the vertical radiation is redirected in a more favorable direction. Now it's time to tune it up.

 

[Marconi]

Here is the Bird Cage model with 8 radials. The model is now showing capacitance at the feed point, so it should take a small inductor stub if I can get it to work.

I have not tried to tune it yet. The stub is next and if it works as intended, then I will try matching.

Anybody have an idea for the stub dimensions. I can only guess it might need to be a 1/4 wavelength.

 

[HomerBB]

Can't recall why the length is what it is. . .