Which antenna device reduces precipitation display to nearly zero on an indicator?

• A. Polarizer
• B. Circulator
• C. Choke joint
• D. Air compressor

Answer: (A)

Controlling the polarization of the antenna signal is how you filter out clutter like precipitation. A polarizer is a passive RF device that passes only one polarization component (or converts polarization) so the receiver is sensitive to a specific polarization state.

In weather radar, precipitation echoes tend to have a polarization signature that can be suppressed by aligning the system to block the co-polarized component while allowing the cross-polarized component to pass, or by using a polarization state that rain returns don’t strongly preserve. When the polarizer is set to block the polarization used by rain returns, the rain signal is greatly attenuated, making the precipitation display on the indicator approach zero. This makes clear-air reflections easier to observe and helps diagnose other radar performance aspects.

The other devices don’t implement this polarization filtering function. A circulator routes energy between ports but doesn’t selectively suppress rain echoes; a choke joint deals with RF choking/impedance issues; an air compressor is unrelated to RF signal processing.