First-Hand:Slide Rule Gives Flight to Tracking Antenna

Contributor

G. Fonda-Bonardi, LSM

In 1949, I was working as a microwave engineer at Hughes Aircraft Company (HAC) in Culver City, California. I was responsible for the design, test, and integration of the RF subsystem for the APG37 airborne fire control radar, which was intended for use in the new generation of jet interceptors and fighter airplanes, beginning with the F86.

The microwave subsystem was comprised of the duplexer, balanced mixer, rotary joints, and antenna. The antenna was to be a parabolic dish with painfully severe specifications on size, weight, gain, side lobe level, and tracking accuracy, which was obtained by conical scanning (monopulse was still in the future). Other groups at HAC were designing and testing the modulator, IF amplifier, display, servo system, and fire control computer.
Then the time came to put it all together and test the system as a whole. The hardware was carted to the roof of the laboratory building and assembled in a small penthouse with a large garage-type door opening to the north, looking over the landing strip of the small HAC airport. When it was all connected, someone pushed the switch. The programmed time delay elapsed, and the set came to life: the antenna started scanning right and left, painting half the way up on the PPI screen a creditable map of the alluvial plain up to the barrier of the Santa Monica mountains. The San Fernando Valley, out in the shadow of the mountains, was dark as expected.
Then someone noticed a blip at the very upper edge of the screen: it was some target that was high, but somewhere far beyond San Fernando, probably coming up from Palmdale. We decided to try and track it. The antenna locked on it right away and stayed locked pointing higher and higher as the target came nearer and larger before finally hitting the limit switch in elevation. Right over our head, at perhaps 3,000 ft high, flew a B36 bomber, the biggest target anywhere in the sky at that time. This was a magical coincidence. Not even Howard Hughes could have borrowed a B36 to celebrate the first activation of our APG37 radar, and the ensuing festivities were to an appropriate scale. Later, an F86 plane was assigned to the development program and was fitted with the prototype radar. While that plane carried out all the test and evaluation flights from the HAC runway, I went on to do other things.
Almost 50 years later, I attended a meeting of the San Fernando IEEE, which featured a slide show that was organized and narrated by D. Pidheny, also an APG37 veteran at HAC who had collected a wonderful set of archival quality photographs that illustrated the history of the evolution of antennas from archaic rhombics to modem dishes and arrays. In the middle of the presentation, there it was on the screen, my APG37 antenna mounted in the nose of the experimental F86 with the radio removed and resting on the ground next to it. And the speaker pointed to me sitting in the audience and said: "And there is the guy who designed this thing." It was gratifying and embarrassing, and all I could find to say was "And I did it using only a slide rule."

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