We are doing a prototype for a gps based tracker. We got a problem in placing the GSM and GPS antenna. Both the GSM and GPS antenna are omni-directional antennas. In forums and application notes, the standard isolation between GPS and GSM antenna is given as >20dB.
How can we measure this dB unit in length. We need to find what could be the minimum separation in millimeter between the two antenna, so as to keep the interference between the GSM and GPS very minimal.