TECH REP

by



Birchard Lee Kortegaard

As we staggered with our duffle bags and other gear down the C-47 ramp at Kimpo Air Base, an Airman directed us toward the Operations Room. Nearing the entrance, I saw a jeep with an Airman holding up a sign "606 AC&W." Pausing, I said

"If you're heading to 606 can you give me a lift?"

"You the new radar Tech Rep?" the A1C asked. He looked me over carefully after I nodded that I was. If he was impressed he concealed it well.

"You're late," he finally grunted, and jumped in the driver's seat.

Late? After a mad-dash transfer from Clark AFB in less than 2 days how could I be late? And late for what?

Confused by the remark, I tossed my gear in the back, climbed in the passenger side and we were shortly heading in the direction of a high hill a few miles away.

Only six months before I had been a passenger on a Fleet Oiler, happily steaming in to San Diego. Two combat tours in Korean waters with Amphibious Forces, Pacific (PHIBPAC) had been enough for me. A Navy enlisted man, ET1, I was planning to ship over for the joys of the Mediterranean Fleet. While waiting at San Diego Receiving I had accidentally seen an ad by Philco Corporation in an LA newspaper for "Field Engineers" with wide experience in military radar and communications equipment.

Navy Techs are a little like fighter pilots in that we also think we're the best, so I took the qualification examination, really just for fun. I could hardly believe it when they offered me a position as a Philco Technical Representative (Tech Rep) at the Civil Service rank of GS-12, equivalent in pay and privileges to Major. But so they did.

Of course I took a discharge instead of shipping over, bought the MIT Rad Lab Principles of Radar book and in two months was back in the Pacific, at Clark Air Base in the Philippines, an "expert" on the AN/CPS-5 Heavy Ground Radar.

I had spent practically every waking moment of those two months absorbing MIT's book and a host of Radar Technical Manuals at Philco's radar school at Warner Robbins AFB, and actually did consider myself an expert. At least, almost. But then, I was barely 22 years old and even more ignorant than most at that optimistic age.

Astonishingly, within a few weeks of arriving at Clark AFB I designed a field modification for their failing target position display scopes (PPI's). My design was perhaps medium-clever but our C.O. was more than kind when he sent a letter of commendation for me to Philco's Tokyo office. His generous act hardened my misconception of reality and, blithely confident I had won a cushy berth at Clark for life, I settled in with a lovely girlfriend, Erlinda.

For two wonderful months I basked in all the perks associated with being a proud member of a Colonial Power, in one of our most beautiful possessions.

So I was more than a little stunned when, less than two days before, I was summoned to Operations and told to pack my gear. The 606 AC&W needed an expert in the CPS-5 ... and I was the lucky winner. Tokyo had unfortunately taken the C.O.'s generous commendation at face value.

All the C.O. could tell me about the 606th was that it controlled fighter intercepts over North Korea, and had top priority for whatever support it needed. Six hours later off I went into the wild blue yonder, on the first of three hops in cargo planes.

To say I was still a little stunned was a definite understatement.

However, there was a plus side. The 606th was West North West of Seoul but still South of the 38th Parallel, right by Kimpo, which meant we had the whole 1st Marine Division between us and the Chinese Armies. The way things had begun I'd half expected it would be atop some mountain right on the Main Line of Resistance (MLR).

After all that how could I be considered late?

The jeep driver kept a gloomy silence and, tired from the hectic two days of hurrying, waiting, and bouncing in cargo planes, I fell asleep, waking only when the Jeep jerked to a stop. We were near the top of a hill, between a heavily sand-bagged Quonset hut with signs labeled "606 AC&W" and "Orderly Room", and a Jamesway hut.

About 50 yards away, at the top of the hill, was the wide parabolic antenna of a CPS-1. The antenna was not rotating.

A frowning face suddenly poked from the Jamesway entrance, and three officers who had been walking down the hill abruptly stopped. One of the officers wore a Brigadier's star.

All observed me intently.

As I hauled my luggage from the jeep the frowning face at the Jamesway moved into full view, on the shoulders of a disheveled person carrying several suitcases. Walking over to me, checking the Tech Rep badge on my khaki shirt, he said "Your bunk will be in the Jamesway."

He climbed into the jeep himself. The jeep bounced off again, back down the hill. As I looked blankly after them, I realized he had also worn a Tech Rep insignia.

A Captain left the group of officers, heading towards me. I dropped my duffle next to the Jamesway entrance, awaiting his approach.

"You're the new radar Tech Rep" he said, accusingly, looking me over carefully. If he was impressed he also concealed it well.

"We'd better go right up to Operations," he said, and headed quickly towards a Quonset hut below several trucks and vans near the hill-top, clearly expecting me to follow. As I caught up with him, the other officers went into the Orderly Room, the Brigadier saying something with apparent emphasis.

"A General? That's the first one I've ever seen," I commented, "I didn't know a Squadron rated one."

"There's a lot of brass up here now. From Kimpo, the 502nd Tactical Control Group and God knows where else" the Captain replied somewhat distractedly.

I looked again at the immobile radar antenna.

Looking around I saw a few more vans near a small antenna farm, probably an FM communications center for the aircraft controllers. I wondered what aircraft?

The C.O. at Clark had said 606 did fighter interception, but a CPS-1 would track all aircraft over North Korea, and would keep track of downed pilots as well, for possible rescue choppers. There would be also be need for operational aircraft control for Kimpo and its Sabre jet fighters.

Waiting at Tachikawa for my connecting flight to Kimpo I'd had a cup of coffee with a Navigator from 19th Bomb Group at Yakota. B-29's flew bombing missions from there, and also from Kadena in Okinawa. Long distances. From what he said the 606th probably gave them position information and also tracked MiGs for their F-86 cover.

I thought of brass from "God knows where else."

I looked at the antenna. It definitely wasn't moving.

When we reached the Operations Quonset I followed the Captain in. By this time, very thoughtful.

There were several officers and Airmen looking through a pile of schematics, and through an open door I saw a Sergeant and an Airman poking into a control panel. When I appeared behind the Captain, they all paused what they were doing and again I found myself under intense scrutiny.

"Captain, just what 'is' the status of the radar?" I asked, haltingly.

The Captain was surprised at my question. He had assumed Tokyo had filled me in, and began to examine me even more closely.

"It's been intermittent for weeks, and went completely down four days ago."

Four days. Four days!! It was less than two days ago that I had been given my transfer.

"Captain, was that Tech Rep who took my jeep the guy I'm replacing?"

"Yes, that was Mr. Garvin."

That Tech Rep had been responsible for this radar, and for this problem. Whatever the circumstances of his being replaced, he should at least have given me a situation report with documentation of everything he had done to get the system back on the air. I could only shake my head in disbelief and laugh,

"Well, if you guys weren't going to shoot him you might at least have given me the chance."

Nobody laughed. Nobody smiled.

Nobody even changed expression. They were not in the mood for joking. 606 was a vital support facility and they needed help, expert help. And they had asked Philco for that help.

And they had gotten me.

Officers and Airmen, all regarded me appraisingly.

Flushing, I tried to let my smile disappear naturally while looking around the Operations area, a row of PPI stations, and the Monitor and Control Rooms for the long-range search and also the height-finder radars. Everything was idle, most of the men not doing anything. The Airman working at the central control panel seemed to just be checking voltages.

Why should I be offended by the seriousness of these men? What were they seeing when they looked at me, after all? Philco must have sent them my records with the copy of my transfer orders, so they would probably have been told my work was highly regarded.

But they would also know I had been a Navy enlisted technician barely six months before, lower rated than several of their own Air Force technicians. No college, minimal actual training by Philco. Physically unprepossessing at 5'7, 135. Twenty-two years old and still with my Navy crew-cut looking about 18. A CPS-5 Expert?

And now I had begun my assignment with a dumb joke.

Most of the officers would be WWII veterans, mostly pilots, in their late 20's. They would have joined the Reserves primarily to keep flying, but when Korea broke out the Reserves were called and they had been assigned wherever needed. In this case, to support positions on this vital radar facility. Why should I be offended if they examined me with obvious skepticism? They had a job to do, and they wanted to believe I could help them, but they were too experienced to take much on faith. As far as they were concerned, I had a lot to prove.

"Down four days! Maybe I should have stayed with the Commandos."

Oh no! Why did I say that? True enough, I had been in our LCVP's for two Commando raids, and for the Inchon assault, and for mine sweeping in Wonsan harbor as well, but so what? Most of these officers had seen far more combat in WWII. To them, I might now seem not only a grinning clown but a braggart as well. I was feeling insecure and showing it, not the best thing when people are counting on you for help.

"Captain, can someone please give me details of the radar's status?" Dead serious at last.

The Sergeant stepped forward, "I guess I can do that."

"Okay. Where is the first place the radar clearly fails?"

"The modulator, I'd say. At least there's nothing going to the antenna."

"Okay. Let's take a look," and I followed the Sergeant and A2C out of the operations hut over to the modulator van. The officers stayed behind, looking at one another.

Okay. Now I can get to work.

Considered functionally, radar is fairly simple.

In essence it is just a brief burst of high energy Radio Frequencies, directed by an antenna outward in a straight line to bounce back an echo off whatever solid objects it may encounter. The same antenna that transmits the beam energy collects these echoes, and a display system converts the time it took each echo to return into a display of the distance from the radar to the echoing object. The big antenna continually rotates, and the echo locations are shown on a PPI, a 360 degree panorama centered on the radar itself.

When desired, Moving Target Indicator (MTI) can subtract uninteresting signals like mountains from the display, leaving only moving objects of interest, such as aircraft. These represent the targets which the radar controllers monitor, direct or intercept.

There is more to it, such as concentrating the beam in specific areas and speeding up its pulse frequency for near-range targets, but by themselves these things are also simple.

Accordingly, "Keep It Simple" was the way I trouble-shot all electronics. A few years later I studied Engineering at MIT, wanting to understand the formal theories of 'why' electronics systems worked and how to actually design them myself, but as a technician it was enough for me just to know what they were supposed to do. It was enough for me to know what signals or controls each sub-system required, and what it was supposed to produce as an output for the next system. When I found a sub-system that didn't produce a proper output when given a proper input, I used basic electronics theory to fix it. This had always been the most effective technique I ever found for a maintenance technician.

By going to the first area the Sergeant said was not functioning, I was cutting to the core of the problem with maximum speed and minimum physical disturbance of the existing system. Connecting an oscilloscope directly to the modulator trigger circuit I had the radar turned on. Instead of the expected input firing signal I saw mostly noise, high frequency and varying in amplitude, forcing the trigger vacuum tube to draw grid current and effectively bias itself out of its functioning range, actually firing the modulator only occasionally.

Trouble with the connecting cable? Coupling from other signals? Soft ground? The problem can't be this easy. They would have found something that simple long before now. Well, the procedure to resolve this was straight-forward.

Going back to the Operations Control console, I verified that the output trigger to the modulator was of correct amplitude and wave shape. Returning to the Modulator van I verified that the received trigger was still useless noise. Snipping the input wire right at the capacitor lead-in to the modulator firing circuit, I verified that the occasional random firing stopped. Simulating a correct trigger with a portable signal generator connected directly to the grid, the circuit responded with the correct output: direct current to charge a pulse-forming network, which a synchronously rotating switch discharged to provide the high pulsed energy needed to excite the magnetron oscillator, which provided the RF energy of the radar beam.

The rotating switch, a sort of three-phase motor, appeared to be working, but the pulse-forming network was simply not being properly energized for the switch to provide the modulating energy to the magnetron.

I've usually found it's better to be "safe than sorry." Although I was fairly certain at this point, and time was critical, I spent the next few hours checking all the sub-systems, both before and following the Modulator, all the way through to measuring the amplitude of the output pulse from the antenna. Since I was using an unsynchronized portable signal generator for pulse simulation I couldn't be sure the timing between the sub-units was correct, but at least I was satisfied that each was in good condition by itself.

Apparently the problem really was this easy, after all. Given a good trigger, at most it should be necessary to tweak the timing a little and the radar would be back on the air.

I had made good use of the Airman all during this time, having him make all the actual connections and turn the equipment on and off, while I sketched the waveforms and recorded the operating voltages. I kept the Sergeant up on the process as well. He watched to see that the Airman made the correct moves and, after each measurement, I showed them that the results were correct for satisfactory operation. Both men began to show confidence that I might know what I was doing.

After everything had been checked, the situation hadn't changed: the problem really was trivial.

The thing I couldn't understand was why they hadn't solved it.

Every radar installation, even with standard versions of the equipment, makes little modifications peculiar to their own needs.

Returning to Operations, I checked all the schematics again to see if this particular installation had made any non-standard installations affecting the transmitter firing system. I checked if they had installed parallel paths for the modulator trigger. They hadn't.

At last, I smiled in satisfaction and asked the Sergeant to just replace the modulator trigger wire and all would be well.

Neither the Sergeant nor the A2C smiled back. After a long pause, the Sergeant asked quietly,

"Are you sure you want us to do that?"

Surprised, very tired after all the travel, working under the strain of knowing the danger to our Air Crews, on edge from deliberately prolonging the danger while double-checking so many details, I snapped,

"Sure? What do you think I'm doing, looking for Easter Eggs? Of course I'm sure. Will you please just replace that wire?"

The Sergeant regarded me calmly a moment, then turned and left without another word. I was immediately sorry for how I'd acted. Philco could raise me instantly to the status of a gentleman, but they couldn't instantly teach me to behave like one.

"Oh Christ," I muttered out loud to myself, "I shouldn't have said that. But why does the Sergeant have a problem with this, anyway?"

"Maybe it's because that signal "wire" is just one of 36 twisted-pairs in a 3-inch, copper-shielded, all-weather cable, carrying every one of our monitor and control signals between Operations and the Modulator Van," came a quiet voice from a corner of the Operations room where the duty Officer, a First Lieutenant, was drinking a cup of coffee.

"And maybe it's because the connectors on that cable are 72-pin copper-jacketed chunks of steel weighing 5 pounds each, and we don't have tools to mate a cable and connectors like that. The Sergeant will have to ask the Colonel to call Kimpo and wake up their cable shop to make one for us, and wake up someone in our Motor Pool to drive a truck down and wait while they do it.

"And maybe it's because all that will mean the radar will stay down for at least another five hours."

As the Lieutenant ticked off these points I slowly began to realize how little I had considered the physical characteristics of 606 AC&W and its radar equipment. It was a mobile installation, not fixed, so of course the equipment was mostly mounted in vans and trucks. Of course these would have complex signal and power interconnection and of course that would mean big, cumbersome cables. I'd measured related signals through the Control cabinet and all through two of the vans without once thinking about the physical nature of those interconnections. In fact, I'd never even seen the insides of a cable like the Lieutenant described, or the mass of wires jammed at the connectors, let alone actually made one up.

Even worse, with a chill I realized there was one more critical check I should have done before committing to such a serious delay. I should have made absolutely sure the cable was at fault and not the connectors mounted on the vans.

In trouble-shooting it's vital to maintain system integrity and not inadvertently introduce other problems ... that way lies chaos. Knowing this, I had been deliberate about not disturbing the physical system while checking it and all its sub-systems. But, once the cable was identified as the probable culprit I should have disconnected it and thoroughly checked the fixed connectors on the structures.

But I hadn't understood the physical nature of that signal "wire."

Considerably shaken by these unanticipated new insights, the hairs at the nape of my neck rose at the Lieutenant's next "And maybe ...

"And maybe it's because we've already pulled and tested that cable three times over the last month."

I had committed the Squadron to an excruciating delay, with absolute confidence. But in fact I had lacked crucial information, information available for the asking had I the humility and wit to invite criticism and suggestions before making a final decision. I just sat there.

After a bit, the Lieutenant asked one of the airmen to take me over to the Officer's mess and ask them to warm me up a meal while the cable was being made up. It was after midnight and I had only eaten a few sandwiches since leaving Clark two days before. I found I was famished, and took my time while eating, thinking over the situation again and again. I always came to the same conclusion.

The problem was simple, and the solution obvious. Building a new cable meant major delay, but there could be no real doubt. I hadn't checked the fixed connectors, but they were almost certainly okay. Grateful to the Lieutenant for arranging the meal in spite of apparently disagreeing with my decision, I idly wondered why he had been so kind. He certainly didn't have to.

When at last I went back to Operations, I found out.

Some Airmen had already verified that the fixed connectors were okay. Then they had hauled the ends of the big armored signal cable into Operations, bending the input and output connectors next to one another, and the Lieutenant was measuring the continuities and insulation strengths himself. Clamping an ohmmeter between the ends of the modulator trigger pair, with an insulation tester between the pair and the ground shield, he quietly demonstrated that they seemed absolutely okay. If that was so, I was obviously wrong and all the work being done on building a new cable was wasted.

"That's the way they looked when we pulled them last time," the Lieutenant quietly remarked.

Somehow I maintained my composure, but my mind seemed to stop working.

I could accept my ignorance of the physical nature of the signal interconnections; nobody's perfect. Still, I was absolutely certain that the fundamental problem was faulty modulator signal delivery. There had to be some explanation for why the connections could all seem okay and still be the problem. At that moment I couldn't think of one.

It's very important to have friends. Friends make life much more pleasant and sometimes, when you need it most, they give you a little help.

"Well," the Lieutenant went on, "of course those connections are just fractions of a millimeter apart. There could be some loose solder, or hair growth, or sharp point that makes contact only in the right position. That could explain the intermittent operation, I suppose. When we tromped around in the vans there could be some flexion on the floor and some tiny movement of the actual cable connections which might make and break a short.

"And pulling the cable for testing might move a short completely so it would test good, like now. A sharp point could even wander to other signal pairs and cause different failure modes. That might explain why we couldn't pinpoint one specific problem and you could, because you kept the structures fixed while you were checking them out.

"And then of course there needn't be actual contact between the connections. They might just be so close that the signals could couple capacitively, by electric fields, making a lot of bridge dividers."

Listening, kicking my brain back into operation, everything he said made sense. I knew I would have thought of those explanations eventually, and others, but time was priceless. It was the Lieutenant who thought of them right then.

"I think you're probably right having us take time out and get a whole new cable built. No way we can check all possible modes of failure. I guess we have to bite the bullet and be sure. "

Ruefully, gratefully, I shook my head,

"Well Lieutenant, what you say rings true but I must admit I hadn't given the cable a thought. If the system doesn't work with the new one, I just hope you guys don't take those five-pound connectors and hit me on the ass with them. At least not more than once or twice."

For the first time since getting off the C-47 I saw someone smile. Not a big smile, but unmistakable. For no particular reason, I started to feel happy. For no particular reason, I started to feel things were looking up.

Any struggle, if it lasts long enough, can bring a man to the point of giving up and just waiting for the executioner.

After five hours passed, and then six, and then seven .. each hour seeming to take forever .. a truck eventually drove slowly up the hill, and came to a measured stop at Operations. Under the stern eye of the Sergeant and ten or fifteen officers, a crew of Airmen carefully secured the replacement cable between Operations and the Modulator van, and even more carefully inserted, screwed and locked its connectors to their fixed mates. Firing the front part of the radar, I was almost dizzy with relief when my scope showed a perfect firing pulse through the cable to the wire I had first clipped from the modulator input grid.

Checking, all the other signals through the cable still seemed good as well. Finally, again inserting a simulated pulse to the grid itself, I verified that the rest of the system still seemed to work; when the magnetron was pulsed it could still deliver RF to the antenna.

With shaking hands, I turned the system off and re-soldered the connector to the modulator grid. Heart pounding, I went to the transmitter system itself, the big rotary Spark-Gap Modulator/Magnetron station, where the actual power delivered at the antenna was generated and visually monitored, along with the resulting echoes. Already standing there were about a dozen officers and several Enlisted men. The General was absent but the Colonel Commanding 606 AC&W was there, along with two other Colonels from "God knows where."

Nodding to the Operations Officer, I requested the radar be fired up, hardly able to breathe as I watched the instrumentation.

The spark-gap motor came up to speed, all the signals came up, pulses were shown to the antenna ... but at far too low an energy and far off frequency! Obviously there was still a disastrous problem with the radar, a possibility I had felt certain I had eliminated. But, clearly, I had missed something! The skin on my face drew taut as I called to the Operations Officer,

"Shut it down!!!! There's something wrong with the drive energy!!"

But I could say nothing further. It was just too much. I had expected to make a few degrees of phase adjustment through the firing system, but a failure like this was unbelievable. The pulse-forming network was not fully charging, but one of the first checks I had made after finding the bad trigger signal was to verify that the PFN had not been damaged and was in fact performing perfectly.

Helpless, trying not to show it, I stood there as everything wound down. The men began talking to one another. Most were looking expectantly at me, some uncertainly but more accusingly. Clearly it was up to me to do something.

But I could do nothing, nothing at all. In a sense I felt as though I was dying, and that it was about time. I had made the drop and my neck anticipated the end of the rope.

As I said, it pays to have friends.

The Sergeant had developed a degree of confidence in me while we tested the entire radar before I requested the cable replacement. Skeptical at that, he had then seen the replacement did, indeed, deliver the modulator trigger correctly. When it was clear the transmitter was now not firing correctly, he was almost as surprised as I was. He looked at me,

"You say there's a drive energy problem? Could it be the phasing?"

At my nod, he grabbed a few wrenches from one of the Airmen and jumped in the trench for the rotor of the modulator switch, almost before it came to a stop. Reaching the switch-shaft linkage, he unbolted the linkage itself and appeared to rotate it 180 degrees.

What he was doing seemed an act of desperation. The spark-gap timing for firing the pulse-network was determined by the phase relations of the motor voltages, but I had checked them, and the Sergeant watched me do it. Rotate the switch linkage itself? Did he think this five-ton rotating mechanical brute could somehow disconnect itself from the factory position? That was simply impossible.

Shattered by this last catastrophe, I just watched the Sergeant re-tighten the bolts and jump back out of the rotor trench. Walking over to me he looked very grim, but somehow apologetic.

"Mr. Garvin had us rotate the linkage, I guess he tried everything he could think of these last few days. I forgot to change the linkage back.

"Sorry."

Made dumb by such information, I could only nod and call to the Operations Officer

"Try it now."

Everybody waited once again, silently, this time having little confidence in a positive result. The radar came back on. The modulator rotor came up to speed, all the signals came up, pulses were shown to the antenna ... and echoes began appearing from 200 miles away!

We were up!!! ... and the world was beautiful.

606 was back on-line.

"Sergeant, I appreciate you giving me the SitRep, I guess Mr. Garvin had to leave to catch his plane."

Obviously Garvin had been worn down to grasping at straws. Anyone can make mistakes under pressure but no rational person would rotate the linkage on that spark-gap if it had ever worked properly. Once having made that mistake, and thinking the control cable okay, Garvin had no chance of fixing the radar. Of course he should have given me a situation report before leaving, but he probably either felt he didn't know how to do it intelligibly or was too embarrassed to try.

If the Sergeant hadn't remembered being ordered to make that rotation it might have taken me a full day to deduce what must have happened. Good men would have been at risk while I worked it out.

Some might have died.

Gripping hands, both of us grinning, both a little proud,

"Thanks, Sergeant."

As soon as it was clear the radar was up and running, everybody became too busy to notice me any more. Most headed eagerly for the Operations Room and I looked in too, one last check to be sure all was well.

All the position monitor and control stations were on line, the controllers already in contact with aircraft operations over the FM links.

I reflected that maybe the 606th really had been sent an "expert on the AN/CPS-5." At least, I had come through for them.

With a little help from friends ...

Walking down to the Jamesway I picked up my gear, still lying where I had dropped it an age ago, and went inside to find a bunk.

For no particular reason, I felt at home.

A: The account is true as far as I can recall it after over 50 years, the essential events being unforgettable, with the following exceptions. To protect the guilty, "Garvin" is a pseudonym. Also, Paul Cunningham, Air Force radar repair with 606 ('50-'52), and Leonard Hanson remember the 606 radar as the AN/CPS-1, a mobile S-band radar similar to the CPS-5, and I have corrected this account where it seemed appropriate. BLK

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