Yes,conducting a proper site survey is highly recommended before installing a mobile signal repeater .here is why a site survey is crucial : 

Identify strongest donor signal : the survey helps you locate the strongest cellular signal outside the building .this "donor signal" is what the repeater amplifies and rebroadcasts inside .a strong donor signal is essential for effective boosting . 

Target covereage areas : the survey allows you to pinpoint the areas within the building that suffer from weak signal .this helps determine where to install the repeater and broadcast antennas for optimal coverage . 

Choose the right equipment : based on the signal strength variations and coverage area ,the survey can hlep you choose a repeater with the appropriate output power and antenna types to best suit your needs . 

Avoid interference issues : a well-done survey can help identify potential sources of interference within the building or nearby ,mitigating issues after installation . 

In short ,a site survey lays the groundwork for a successful mobile signal repeater intallation .it ensures you target the right areas ,select the most suitable equipment and achieve the desired signal improvement .