Back in 2004, I got a job at Honeywell Aerospace testing a newly designed airborne weather radar. We had a dozen test stations spread out in our engineering lab, and each station had a full set of equipment: antenna, transmitter, receiver, signal processing box, and radar display.
We put attenuators on each antenna so we didn’t radiate ourselves. I spent a lot of time on the test stations running random tests and arbitrarily switching dials to try and throw the system into an unknown (and unwanted) state.
Most of the time I’d just find subtle display problems, and I’d work with a DSP guy named Frank to replicate it so he could go into the software and figure it out.
Most of the stations were situated a ways away from each other in the lab. Two stations were side-by-side. While doing my random testing and button mashing, I noticed that the display on test station A went buggy when I flipped the radar on station B to a particular operational mode.
I quickly determined it was a faulty attenuator on station B that would induce some interference on station A, but I decided to have a little fun with the situation before fixing it for good.
So, I went back to my desk and wrote up a phony “system change request” regarding the “phantom display artifacts” seen on the weather radar. I kept it vague and cryptic.
Frank saw the fake SCR in the log sheet and asked me to come to the lab and show him the odd behavior. Before heading out to the lab, I told another coworker, Rita, about how putting the radar on station B in a certain operating mode made the display on station A go buggy.
We hatched a plan to plant Rita over at station B while I showed Frank the goofy behavior on station A.
Frank and I went out to the lab, and I said something like “yeah, it’s really weird, noise just pops up on the display when I *SNAP* my fingers like this”. Pop, up comes the noise (Rita switching the dial on station B).
“And then it just goes away with another SNAP.” Back to normal.
Frank got confused really quick! I demonstrated the finger snapping a few more times and Frank just got more and more perplexed. He started wondering about how an audio tone would somehow couple in to the system. I suggested he try snapping his fingers, and when he’d go *SNAP*, nothing would happen.
Rita, over on the other station, was by now giggling pretty good. Frank sat there and scratched his head. Bewildered, he said he’d have to go back and think about it for a while.
We eventually let Frank in on the gag. At first he didn’t laugh, but he got over it. And then he went back out to the lab and pulled the same prank on somebody else.
My first job out of school was for a hardware virtual reality company (mid 90's). We had a simulated control panel, consisting of large metal open frame (~6' high by 8' wide), with a 2-axis cable-driven panel (~18"x18") able to traverse the entire area of the frame, under control of large servo motors at the bottom corners of the frame.
The goal was to be able to simulate a large control panel (such as an aircraft instrument system), using the smaller panel with a set of generic switches and buttons. To do this, the 18x18" panel had to be able to move very quickly, and could go from standstill on one side of the large frame to the other in less than 1 second. The panel was also pretty heavy, since it had its own set of small servos and controls for the switches and instruments.
I had a test program that enabled me to command the panel to random XY locations within the frame, and set acceleration/velocity profiles.
We had a VP who used to come in to the lab and busybody the engineers over trivial matters - one time she'd actually made somebody count the sheets in a 500-sheet ream of paper, to ensure the paper company wasn't ripping us off. Generally, she didn't have a clue technically.
One day after having had enough of her antics in preparation for a customer demo, I decided to have the system "fail" two hours before the demo. While she was berating one of the other engineers, I ran the random-location program at 10x speed, with the servos going full bore, and the switches on the panel randomly re-orienting themselves under control of their local mini-servos.
With the metal frame shaking under the accelerations, I screamed "The Flux Capacitor's blown! We need to shut down the system!". My colleagues immediately got it, and jumped up to "help" me. We received orders from the VP to fix it in time for the demo, and then she went to lunch. We went to lunch ourselves, and I reported after that I'd replaced the Flux Capacitor, and all was well...
Blog Make a Frequency Plan Tom Burke 17 comments When designing a printed circuit board, you should develop a frequency plan, something that can be easily overlooked. A frequency plan should be one of your first steps ...