"Drone detection" covers a range of techniques, but the most common and most reliable starting point today is detecting the Remote ID broadcasts that compliant drones are required to send. Understanding the basic mechanics helps clarify what a detection system is actually doing when it puts an aircraft on a map.
Wi-Fi and Bluetooth receivers
The FAA's Remote ID standard specifies that drones broadcast over Wi-Fi or Bluetooth — the same general radio technologies used by phones and laptops. A Remote ID receiver is tuned to recognize these specific broadcast formats, decode the message fields (identity, position, altitude, velocity, and so on), and pass that structured data to software that can plot it on a map and log it over time. Because the broadcast format is standardized, a properly configured receiver can pick up compliant aircraft from any manufacturer.
Receiver placement and antenna configuration affect how much airspace a given installation can cover, but no receiver can pick up a broadcast that isn't being sent, or one sent by a non-compliant aircraft.
Where other sensor types fit in
Because Remote ID only identifies aircraft that are broadcasting it, some deployments pair Remote ID receivers with additional sensor types — general radio-frequency (RF) scanning, for example — to build broader awareness of activity in the surrounding radio environment. These additional layers work differently than Remote ID detection and are typically configured based on a site's specific risk profile and requirements.
The right combination of sensors depends on what an organization is trying to accomplish. A facility mainly focused on regulatory compliance and coordination with known operators has different needs than one trying to build the fullest possible picture of all activity nearby.