why these antennas are twins. You have a receiver and a transmitter.” “
“But you can’t suppress the first signal coming in?”
“Nope. They get one free look. The very first incoming pulse will not be muffled. Nor, in this generation of this device, will the second. See, you can’t get a pulse repetition frequency until you have received at least two pulses, which you must have to time your outgoing pulses, the muffling pulses. But with existing radars, the return from one pulse will be treated like static. The cathode- ray tubes need a lot more pulses than that.”
“And when the guy painting you stops transmitting, you beacon one more time?”
“That’s the problem Harold and I are working on right now- You see, after the first pulse comes in, and the second, the com- puter then has to figure it all out and start transmitting. Right now we’ve got the computing time down to about ten billionths of a second. That’s not enough of a clean chirp to let any existing radar get a definable return. If the next pulse doesn’t arrive right on time, we’ll stop the muffling pulses ten nanoseconds later. Just need to fix the software, the XY dipole and…” His voice fell to an incoherent mumble.
“Why wouldn’t a second radar that is in a receive-only mode see you beaconing to the first radar?”
“Bistatic radar? It would,” said the genius in jeans, “if all we were doing was pulsing straight back at the transmitter. But we aren’t. We’re pulsing from a series of antennas all over the plane to neutralize the reflected signal. Knowing how much to radiate, pre- cisely enough yet not too much, that’s where the computer really makes this thing work. First you must know the exact reflective characteristics of the object you are trying to protect — that’s your airplane — and put that data into the computer’s memory. Then the computer calculates the scatter characteristics of the incoming sig- nal and tells each of the two hundred transmitters positioned over the fuselage and wings and tail just bow much to radiate. All of the transmitters have to radiate in all directions. And this whole thing has to work very, very quickly. No computer was fast enough to handle this until superconductivity came along. See, to make the electrical signals move along fast enough to make this work, I’ve had to super-cool my computer in a tank of liquid hydrogen and encase the wires to each of die antennas in this special sheathing. That lowers the resistance just enough.” He gestured to a row of pressure bottles that stood in one corner of his workshop. “Still, there’s so much computing involved we had to go to a distributed system with multiple CPUs.”
Jake felt like a schoolboy who hadn’t done his homework. “But how does the outgoing radar signal cancel the incoming one?”
Dodgers stepped over to a blackboard standing in the corner. He looked around—“Where’s the rag?”—then used his shirt sleeve to erase a spot “Harold, where’s that blasted chalk?”
“Here, Dad.” The young man picked up a piece from a nearby bench.
Dr. Dodgers drew a sine wave on the board. “Do you know anything about radiation?” he asked Jake gruffly.
Jake nodded hesitantly as he traced a sine wave in the air with his finger. He knew from experience that claiming knowledge in the presence of a physicist was not a good idea.
“It moves in waves,” Dodgers agreed dubiously. He drew an- other sine wave over the first, yet the peaks of the second were where the valleys of the first one wera, and vice versa. “The first tine is the reflected signal. The second line is our outgoing signal. They cancel each other.”
Jake turned to Fritsche with raised eyebrows. Fritsche nodded affirmatively. “This principle has been known for a century. Dr. Dodgers’ real contribution — breakthrough — has been in the area of superconductivity at higher temperatures than anyone else has been able to achieve. So he asked himself what computer applica- tions were now possible that had been impossible before.”
“And came up with this one,” Jake muttered, for the first time seeing the intelligence and determination in that face under the bill of the cap.
“Let’s fire it up,” Dodgers suggested. “Helmut, if you will be good enough to take Captain Grafton and Harold up to the out- house, I’ll do the magic down here.”
As Harold drove the rental car along a dirt track through a field, Jake asked, “How’s security out here?”
“Security?” the young man said, his puzzlement showing. “The neighbors are all Presbyterians and Methodists and they think Dad’s a harmless loony. Their kids get curious and come around occasionally when they’re out of school or in the evenings, but we don’t tell them anything and they wander off after a while. Just got to keep them away when we’re radiating. Been having some trou- bles with the power company from time to time. We sure pull a lot of juice when we’re cooling down that hydrogen and they’ve dropped the load hereabouts a time or two.”
“We had the head of the Federal Power Commission call the president of Pacific Gas and Electric,” Fritsche told Jake.
“The district engineer still comes around occasionally, though,” Harold continued. “I think he’s harmless. Dad’s been feeding him a line about experimentation with electromagnetism, and he bought it ’cause he’s local and knows Dad’s a dingbat” The youngster goosed the accelerator to take them through a mudhole in the road. “Nice car. I’d sure like to have a car, but Dad — with the church and all…”
The radar was mounted in the old outhouse on the bench where the seats once were. It radiated right through the open door. Har- old Dodgers removed a padlock from a flap door at the back of the structure to gain access to the control panel and scope. “This is an Owl Screech radar,” Fritsche told Jake. “We borrowed it from the EW range at Fallen.” The Electronic Wufare range at NAS Fal- lon, Nevada, provided realistic training for fleet aircrews.
“Wonder where the U.S. Navy got this thing.” Owl Screech was a Soviet-made gunfire-control radar.
“From the Israelis, I think. They had a few to spare after the 1973 war.”
The drone of a jet somewhere overhead caused Jake to scan the blue sky. It was high, conning. An airliner or a bomber. A row of trees higher on die hill waved their leaves to the gentle breeze. So warm and pleasant here. Jake sat down in the grass while the redheaded youngster worked at the control panel and Helmut Fritsche observed.
“We’re not getting any power,” Harold announced. “Can I bor- row the car and run back to the shop?”
“Sure. You have the keys.” Harold eased the car around and went bumping down the dirt road. Fritsche joined Jake in the grass.
Jake tossed a pebble at the outhouse. The stone made a satisfying thunk. “What’s the plan to get this gizmo into production?”
“Normally we would do engineering drawings and blueprints and take bids, but due to the time constraints and secrecy require- ments, we’ll have to select a contractor on a cost-plus basis. The government will retain title to the technology and we’ll pay Dodg- ers royalties.”
“What contractor will get it?”
“One with the staff and manufacturing capacity to do it right and do it quickly. Probably an existing radar manufacturer.”
‘”Cost-plus. Isn’t that beltway French for ‘can’t lose’? And the contractor’s engineers will see all the technology and have a leg up on bids for second- and third-generation gear.”
“Yep.”
“And if they can dream up ways to do it better, they can get some patents of their own,” Jake tossed another pebble at the out- house. “Gonna be a nice little plum for somebody.”
“Yep.”
“Good thing all the guys in our shop are honest.”
Fritsche sat silently, weighing that remark, Jake supposed. “I guess our people are like everyone else,” Fritsche said at last, with- out inflection. “People are pretty generally alike all over.”
“Why was Strong killed?”
“Don’t know.”
“Any ideas?”
“Some. But I keep them to myself. I try not to gossip. There are laws against slander.”
Jake Grafton stood and brushed off the seat of his trousers. “A river of money flowing along in front of a bunch of guys on middle- class salaries, a bunch of guys all humping to keep their bills paid until they get middle- class pensions and form letters of apprecia- tion from the government. Everybody’s honest. Nobody’s tempted. Makes me want to salute the fucking flag and hum a march.” He looked down at Fritsche.
“I have no facts. Captain,” the scientist said. “None.”
Jake looked around, trying to think of something to say. He gave up and strolled up the hill to the trees,
