Secondary Surveillance Radar in ATC Systems: A description of the advantages and implications to the controller of the introduction of SSR facilities

NORMALLY, the SSR interrogator is used in conjunction with a primary radar, the two systems being complementary. Primary Radar depends on the reflection of radio signals. These signals have to be strong enough to survive the two‐way path, therefore the emitted signals must be of relatively high power. Signals reflected from hills, trees, buildings and precipitation will also be received and displayed on the PPI, thus causing clutter on the display and confusing the picture.