We both joined the Virginia Tech faculty in 1969, beginning over 50 years of collaboration and friendship. In 1972, we began work on a NASA-sponsored project to characterize propagation of 10–30-GHz signals on satellite downlinks. Rain attenuation (fading) and depolarization (changes in wave polarization that would introduce cross-talk between channels) were the big concerns, and the first step was to measure and analyze these effects on a terrestrial path. To do this, we built a 1.65-km, 17.65-GHz radio link from a transmitter on an elevated platform to a receiver on the roof of a campus building. Both the transmitting and receiving antennas were parabolic reflectors with dual-polarized feed horns set for linear polarization 45o on either side of vertical. An electromechanical waveguide switch routed the transmitter output to each polarization in turn on a 4-s cycle, and we measured the output of both receiver channels. In clear weather, the copolarized channel output (the one corresponding to the transmitted polarization) was about 45 dB above the cross-polarized channel output. In heavy rain, this difference could become as low as 10 dB, as raindrops scattered energy from one polarization to the other.
It was the Thursday afternoon before our first crucial NASA visit on the following Tuesday. Bostian was looking at the received signal levels as printed out in our laboratory when the cross-polarized signal started jumping around and then stabilized at a value equal to the copolarized signal. Our rooftop receiving antenna was in an area where housekeeping staff occasionally took breaks, and our first thought was that someone had put something in the radio path. Unfortunately, it was not this simple. We worked the rest of that day and every day after that (Saturday and Sunday included) starting at the receiving antenna and checking every component and system, without success. By Monday morning, the only thing left was the transmitting antenna. Stutzman climbed up on its elevated platform, looked into the translucent plastic covering the mouth of the feed horn, and began to yell. He found the problem—a very dead housefly inside the feed.
It turned out that, on the previous Thursday morning, a graduate student had disconnected the transmitter from its waveguide and left the waveguide open for several hours. The fly entered the waveguide and somehow made its way through about 4 m of microwave plumbing and ended up in the feed horn, where it could see light but not escape. With the transmitter replaced, the microwaves soon cooked the fly, and it died at the point in the feed where it could scatter the most energy from one polarization to another. That fly must have been a genius at navigating mazes—too bad we couldn’t have given it to the psychology department.
We removed the fly, and the NASA visit went well. Stutzman still has the dead fly in a bottle—a memento of our first big project.
