This paper presents a fully numeric amplitude-demodulation based technique to enhance simple electromagnetic analyses. The technique, thanks to the removal of the clock harmonics and some noise sources, allows efficiently and visually disclosing the leaking information. This technique has been applied to three different different modular exponentiation algorithms, mapped onto the same multiplexed architecture able to perform the exponentiation with successive modular multiplications using the Montgomery method. Experimental results demonstrate the efficiency of the applied demodulation based technique and also point out the remaining weaknesses of the considered architecture.