Thank you to whoever provided the coordinates for the model of this antenna.

I wrote them down and entered them when I saw them in your posting but
the original email has been automatically removed from the folder in my
email client.

There has been a lot of discussion and side issues raised from my
original post but I am grateful for you taking the time to provide the
information for me.

I am a novice with regard to antenna theory and have no previous
experience with antenna modeling. Your post has given me a good starting
point.
I entered the coordinates and (beside initially selecting wavelengths
instead of inches) the model ran fine.
I was then able to scale it up to the frequency of interest (920 MHz)
and now I am playing with the sleeve diameter, sleeve length and
radiator length to observe how these are effecting radiation pattern and
SWR.

There was also mention of a book regarding basic antenna modeling, my
next step will be to purchase a good book to help me understand the
process and limitations etc.

Thanks again

Regards

David Huisman