As can be seen there is a very large and wide back lobe!
Another source of concern are the reflections from side lobes that can sometimes cause false targets and/or “noise” on the display.
The longer the antenna relative to the radio wavelength is the narrower the main lobe will be but the price to pay is that more side lobes will be created. In receiving antennas, side lobes may pick up interfering signals, and increase the noise level in the receiver.
Side lobes can be responsible for creating false steady targets in the radar screen. In navigation best practice is, if possible, to always evaluate each target.
Another effect is when a large ship is close to ours the side lobes can cause a typical interference as shown.
In military radar systems these side lobes turn out to be a very significant weak point in any radar system that can be used to create confusion and misrepresent the target. They are considered as the Achilles heel of such systems,
Multiple false targets with multiple headings can be generated with a single side lobe transmitter. The radar antenna is pointing in the wrong direction when the largest return signal is received.
Combining the false signal with the real signal creates a false signal that appears real to the radar. The radar antenna is actually pointing in a significantly different direction from you. The error can be as much as 30 degrees. So, if this acquisition radar directs a weapon at you, it’s really pointing in the wrong direction.