Oops, just found this in my Honeywell RDR4000 manual.
EFFECTS OF INTERFERING RF SOURCES
An interfering radio frequency (RF) source operating at a frequency close to
the radar’s operating frequency can create unusual returns on the display
(see figure below). These returns will appear as a single wedge of radar
return that extends from very close range (< 5 nm) out to maximum range for
the selected range scale. The wedge will typically cover from 3 to 5 degrees
in azimuth and may, depending on the strength of the source, appear from
green to red. These returns are caused by Continuous Wave (CW) sources of
RF radiation.
CW RF sources that can cause this effect include:
• CW Military Radar
• Radar Jamming Equipment
• Satellite Uplink Equipment
Adjusting the manual gain may help alleviate the effect of the interfering
source but the effect will not completely disappear until the interfering source
is no longer in the radar’s field of view and that area of the memory has been
refreshed.