Radar calibration has received constant attention since the birth of radarmeteorology in the 1950s. Despite the huge impact of a calibration bias on radar-derived precipitation amounts, one has to admit that one still lacks of a simple and reliable method to calibrate absolutely conventional radars. In this paper, we investigate alternative ways aimed at improving the relative monitoring of the French radar network. They consist in : 1) following the level of near-range ground targets return, 2) performing comparisons with neighboring radars and 3) performing radar - rain gauge comparisons with a dense rain gauge network. Six months of data from the Trappes radar located near Paris in an urban environment are used to design the clutter, radar - radar and radar - rain gauge indicators and evaluate the potential of each of them. The advantages and drawbacks of each indicator are discussed. Preliminary results show that the clutter and radar - radar indicators are powerful tools to evidence abrupt changes in the radar calibration.