Simulation tool for PA with loop antenna

Hello everybody, what simulation tools should be used for twin differencial power amplifier on 8.1 MHz with low pass filter and balanced big loop antenna ("double eight" is the first antenna for the first differencial amplifier and "single eigth" is the second antenna for the second differencial amplifier). Each amplifier has low pass fiilter in the output (between MOSFET and antenna).
Thanx a lot