Help on PIFA in the frequency of 138 MHz to 174 MHz

Hi,

I am currently designing a PIFA. The frequency band aims at covering 138MHz to 174MHz. VSWR=2:1 for all frequency bands. Dimension restriction: Must be compact design, height must be less than 6in. Ground size: O.D. 3feet max. Power rating: 200W min total for all channels.

Would anybody like to give me some suggestion about how to make a PIFA satisfying VHF/UHF band? What's the dimension I could start with?

Thank you so much in advance.