Cold Atom Clocks, Precision Oscillators and Fundamental Tests

We describe two experimental tests of the Equivalence Principle that are based on frequency measurements between precision oscillators and/or highly accurate atomic frequency standards. Based on comparisons between the hyperfine frequencies of 8 7 Rb and 1 3 3 Cs in atomic fountains, the first experiment constrains the variability of fundamental constant. The second experiment is based on a comparison between a cryogenic sapphire oscillator and a hydrogen maser. It tests Local Lorentz Invariance. In both cases, we report recent results which improve significantly over previous experiments.