IEEE History Center: Pearl Harbor Revisited, by Joe Lockard | 
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Six radio sets, SCR-270-Bs, arrived at Oahu, TH (Territory of Hawaii) in late July 1941. At last the unit in which I served, the Signal Company Aircraft Warning Hawaii, could begin to fulfill its mission. This was the first "radar" equipment we had ever seen. Prior to the arrival of this equipment we trained in field communications and studied radio theory. There were about 200 men in the company, quartered in an old wooden barracks on the Kole-Kole Pass road, a long walk west of the main quadrangles of Schofield Barracks in central Oahu. The SCR-270-Bs were soon dispersed about the island, and on-the-job training began. There was a unit at our barracks at Schofield; one at Kaaawa; one at Koko Head; one at Fort Shafter; another at Waianae; and the sixth unit at Kawailoa. All these units were nearly at sea level except for the one at Koko Head. The Koko Head unit was at over 600 feet elevation. Those of us who were actually operating the equipment were on a 6-week rotation schedule. In August and part of September, I was at Fort Shafter; then through October at Koko Head, then back to Schofield. The sojourn at Koko Head was most interesting. There were six of us living in an old wooden shack located atop Koko Head next to the SCR-270-B. The building apparently at one time was used for coast watch, for there was an observation platform on its roof. Below this site to the east is the beautiful Hanauma Bay. The SCR-270-Bs performed well. Our operating schedule varied. Some mornings we were up at 3 a.m. and sometimes late at night. On September 27 we participated in an exercise with carrier based aircraft, which were successfully detected and intercepted. The Navy planes were picked up almost as soon as they left the carrier over 80 miles off shore. In early November I returned to Schofield. Based on the recommendation of Lt. Col. Powell, the SCR-270-B at Schofield was relocated to the north side of the island at a place called Opana. The unit was moved in late November. I was assigned to this unit, and we were quartered at Kawailoa 5 or 6 miles from the Opana site. We lived in pyramidal tents over wooden platforms on the beach, hardly hardship duty. The Opana site is a knoll in the foothills of the Koolau Range. It overlooks the little crescent shaped bay called Kaweta, and is just west of Kahuku Point, which is the northernmost tip of Oahu. December 7,1941 was a Sunday, and I drew duty for the 4 a.m. to 7 a.m. operating schedule at the Opana station. George Elliott, a recent transferee from the Air Corps, was assigned as my plotter. Since it was Sunday it was a skeleton crew. We were taken to the Opana unit by truck late Saturday afternoon to spend the night at the site. We had a pup tent and an alarm clock to rouse us for the 4 a.m. start of operations. At 4 a.m. we were operating and in communication with the Information Center at Fort Schafter. Ground line directly connected the plotter with a plotter at the display table where markers representing detected targets were moved about on the scaled board. The SCR-270-B at Opana was at an excellent elevation. It was a little over 500 feet above sea level with a fairly steep slope descending to the narrow coastal plain. The sea was about a mile away. Inland from the antenna the ground sloped downward slightly before slowly rising to the heights of the Koolau Range. This caused interference that extended over 20 miles. At a distance of about 90 miles to the northwest the island of Kauai returned a strong signal. Southeast were signals from the island of Molokai, and two peaks on Maui, Puu Kuki, and Haleakala. These peaks were over 100 miles from the antenna. We used them to peak up our antenna tuning. Northward is nothing but Pacific Ocean all the way to the Alaskan peninsula over 2000 miles away. During the 4 a.m. to 7 a.m. operation period, there was little activity. We continued operating after 7 a.m. so that Elliott could receive training on the equipment. As I started to instruct him, a huge "echo" appeared on the oscilloscope in an almost due north direction, and at a distance of about 137 miles from the antenna. I made a few quick checks to determine if the equipment was functioning properly, and noted that the target was moving. The display on the SCR-270-B was a small round black and white cathode ray tube (CRT) that showed a baseline with projections above the line representing information from the antenna. Linear displacement along the baseline represented distance from the antenna. The baseline could be shifted to cover the range determined by the pulse rate and was calibrated in miles. To the left of the screen at zero miles was the main pulse from the transmitter, and the pulses from the antenna's backward emission reflected from the surrounding terrain in the case of the Opana unit, this obscured about 20 miles of forward range. The height of the "grass" above the rest of the baseline was dependent upon the sensitivity control. Reflections from objects were taller, thicker blades of "grass" we called echoes. The only means of differentiation between mountains, ships, and planes was movement. Azimuth was determined by sweeping the antenna back and forth across an echo to locate the point of maximum size. This could be complicated by the antenna tuning, and by the phase relationship between direct and reflected waves as the target moved. If they arrived at the target in phase the echo was enhanced; if they arrived out of phase the echo was diminished. Of course, the azimuth indicator had to be properly oriented. There was no means to determine target altitude. I continued to track the incoming flight and Elliott plotted it. I knew it to be aircraft by the rate of movement along the baseline. The first plot was recorded at 7:02 a.m. The echo continued to move along the baseline at maximum height of the display. The reason for the lack of signal fluctuation was the large number of aircraft, but of course we didn't know that. The siting couldn't be reported on the plotter's line for there was no one at the other end of the line at the plotting table. Elliott called the switchboard operator at the Information Center on our other line and told him about the flight. Joe McDonald looked around the center and found an Air Corps lieutenant. Lt. Kermit A. Tyler and I talked over the phone, and I gave him the information about the incoming flight. I stressed the unusual nature of the target, its direction and size. He told me not to worry about it. I later learned that he assumed that it could be a flight of B-17s coming in from the West Coast. We continued to track and plot the flight, all the while wondering what it could be. Actually, this was the first use of radar in warfare by U.S. Military Forces, but we didn't know that at the time. I lost the echo in the background interference about 7:39 a.m. and some 20 miles offshore. The truck arrived to return us to Kawailoa and breakfast. We closed up the unit, climbed into the truck, and drove down the narrow dirt road to the main highway. About halfway to camp we passed our other truck with the rest of our operating crew speeding back toward Opana. They excitedly waved and shouted at us as they passed, but we couldn't understand what they were saying. As we proceeded toward Kawailoa we saw huge black billows of smoke rising high into the sky in the direction of Pearl Harbor. We knew something had happened but we didn't know what it was. When we arrived at camp, we were told that the Japanese had attacked. We knew immediately that what we had tracked were the Japanese attack planes. The men in the truck we passed on our return to camp reopened the Opana station upon their arrival. We moved our camp to a group of shacks seasonally used by plantation workers called Kawela Camp #2. It was within walking distance of the Opana station. The SCR-270-B now operated around the clock. Two machine gun positions were established in defense of the unit. All were armed and waiting for the other shoe to drop. No invasion materialized. Radar was on Oahu a scant 4 months before the attack. In that time the network was established, an Information Center was built, and all personnel were trained. The SCR-270-B at Opana was in place and operational less than 2 weeks prior to December 7. The incident at Opana is one of those "what if" footnotes in history. Of all the scenarios one can devise about this event, the most intriguing to me is this: what if the attacking planes had left their carriers 15 minutes earlier?
The
original article was published in
Reflections
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