Hedy Lamarr did invent spread radio, wherein several weak frequencies
are used instead of one strong frequency, to enable clandestine
transmission and hard to interfere with (hard-to-jam) reception.

Radar goes back to Tesla for origins of idea that waves are reflected
by metal objects, such as boats.

Will Herzog, K2LB
Rochester NY

 [ I believe that the Antheil-Lamarr patent described synchronized
 [ frequency hopping, which is widely deployed today in tactical radio
 [ systems.  The "spread spectrum" system, using a noise-like broad-
 [ band signal, is a 1980s development which already is in use in
 [ at least one cellular telephone system and also in many homes:
 [ the hand-held 900 MHz wireless telephone!  -- Robbie