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The Coast Star |
John Marchetti in front of building 20 - January 1999  |
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How do you locate and kill the enemy who is shooting mortar shells at you, from over one mile away, that are smaller than a soda can and packed with explosives? According to Dr. Harold Zahl, "General MacArthur's staff pleaded for some breakthrough in technology which would help in the quick determination of the ever-shifting positions from which these hell-created torpedo rain-drops were fired - generally in bursts of hundreds, and then to a new firing position." Only one radar laboratory stepped up to meet this 1943 challenge. Dr. John Marchetti of Camp Evans had the breakthrough idea: "If we could only detect the shells as they clear the jungle |
foliage, say a few hundred feet above the firing point,
we could easily extrapolate down to the approximate position where the
mortar was before they could change their location. Then we could blast
the hell out of them before they could change their location."
Dr. Marchetti's idea was to combine a new, very powerful and relatively lightweight generator with Dr. Zahl's custom designed vacuum tube, the VT 158. Dr. Zahl's tube ran at 600 megacycles sending radar waves with 50-cen-timeter wavelengths at its target. A Japanese mortar shell was nearly half this wavelength in length and it should send back a glowing radar reflection. A team went to work in building 9020 at Camp Evans to modify a radar called the AN/TPS-3 with the VT- 158 and the new generator. In a few days, they had an experimental model ready. They took it to isolated Island Beach to |
test. The idea worked, with each mortar fired there appeared
a distinct "blip" on the radar scope.
When General MacArthur's staff was advised the problem was solved, they ordered the equip-ment as soon as possible. There was no time for contracts or plans - they had to be built immediately at Camp Evans. Building 9020 and the surrounding Dymaxion Deployment Units were turned from a laboratory into a production shop. Twenty engineers and a secretary worked day and night. They fabricated 12 units taking any parts they could from other radar units and sending soldiers to radio supply stores for needed parts. They also trained the GIs who would operate the radar units in battle. Besides being deadly to enemy mortars, these radar units were only a few hundred pounds. Unlike any radar designed before, these could be loaded into a land-
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| ing craft and set up in 30 minutes to protect
landing beaches from mortar attacks or enemy planes.
Finally after 96 hours of continuous work, the units were completed. The units and freshly trained operators were loaded onto trucks and driven to Newark Airport. They were flown to the Pacific in time for the next island assault. The radar engineers and Miss Helena Schroeder, the secretary, when home for well-deserved rest. The Zenith Radio Corporation would produce over 900 of these radars. They would see action during the remainder of the war - 24 were landed on D-Day in Normandy and they were even used years later in the Korean War. This story was retold in the official Signal Corps history of WWII, and many radar history books. In 1964, Popular |
Electronics described the VT 158 as, "the
secret tube that changed the war."
Dr. Marchetti has been called the "human dynamo" and, "one of the Army's most brilliant electronic engineers." Dr. Marchetti, like many WWII engineers, worked 15-hour days and many weekends to help defeat the Axis powers with electronics. To Dr. Marchetti, the honors from Britain and France did not compare to the day a Marine captain visited him at Camp Evans shortly after the war. The captain wanted to thank the man, face to face, who made the radar that saved his men from being killed on the beach by those Japanese mortars. [Fred Carl is the director of the Infoage Science-History Center at Camp Evans.] |
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