setup simulation and sweep simulation results in HFSS

I'm trying to simulate a spiral small antenna in HFSS.my antenna should work at 434 MHz.Firstly i did a fast sweep simulation( between 400 MHz and 600 MHz) to determine the resonant frequency of my design.then i did a setup simulation in this frequency to have radiation parameters. My problem is that during the 2 simulations i have not the same results of S11 in the resonant frequency. I tried to modify target and convergence parameters but it doesn't change anything.
In an other way,i did a sweep simulation at 500 MHz i got 460 MHz as resonance frequency with S11=-15dB.
Then i did a setup simulation in one point 460 MHz to have radiation parameters in that frequency i got S11=-0.01 dB.
So How can i proceede to have radiation parameters in resonant fraquency after a sweep simulation

Archive your design with WinRAR and post here so we can take a look.