Chaotic RF generator with bipolar transistor is proposed. Mathematical model of the generator, oscillator with 2.5 degrees of freedom, is investigated. Generator dynamics is analyzed with Advanced Design System (ADS) software using parameters of a real transistor, properties of the board substrate are taken into account by simulation. ADS simulation results are compared with experimental data. It is shown that the use of ADS software for analysis of generator dynamics and account for the board properties and topology allow to get simulation results closer to the experimental one.