simulate a monopole antenna working at 300MHz using CST

Hi,
I am simulating a monopole antenna using CST.
The desired operating frequency is 300MHz. The strcuture is very simple.
My conducting metal has radius 1.275mm (592mm long), and is covered by dielectric material and then a metal shield.
The problem is, every time I simulate with frequency solver, the error message will comes out:"The relative change of the individual object's volume change is large, which indicate a failure of the adaptive mesh refinement. ."
Does this mean my conducting metal is too long compared to the small radius? But in order to work at this frequency, the length must be large...PLease help me~Thank you a lot!
Even I reduce te length of antenna to 200mm, the same error mesage comes out...I'm totally confused

The duplicate post was found in Electronic elementary section, and you were guided to post here. But you may always request the moderators to move the thread to the required section, instead starting a new thread which will be the duplicate content and likely to get an infraction. Anyways, your old thread is now deleted.

ok..Thanks~