Chapter 9 Goin up the country –Part 2

I looked over the tired old radar. These units had been in production since 1954 and this one had a low serial number. It would run, sort of. The cooling blowers and the signal-sweep drum would turn but there were no white blips on the radar screen. They had left it running even though it didn’t work. The noise was a cheap insurance policy.

The Capt. said the unit had been in the bush for nearly a year and hadn’t been maintained. They were afraid to shut it down because of the constant threat of attack. They did move it around every couple of weeks, he said but that required a shut down of only a few minutes. I asked if he could get my equipment moved nearby and in a few minutes I was surrounded by equipment cases.

The radar was running but the transmitter was not powered on so I opened the transmitter cabinet threw a couple of interlock switches and made a quick preliminary check. The transmitter voltage meter read near zero. The immediate problem was the transmitter tube. It was a magnetron and normally had to come from the American depot at Long Binh. But Col. Suel had made sure I got the running-spares kit I had asked for so I had a complete set of running spares including a magnetron.

I suspected that, as was often the case, l there had been a cascade of problems leading up to the transmitter failure. Ultra High Frequency Radars like this one use square tubes called waveguides between the transmitter tube and the antenna. Unless properly maintained, the waveguides grow mold inside that interferes with the transmitter causing it to overheat. We couldn’t know that until I replace the magnetron and fired it off. First I unpacked the big Spectrum analyzer AA had wanted me to leave behind. I plugged it into the generator and powered it on. Then I plugged it into the test port on the T-R tube. The transmitter had about 10% of its usual power so I could get a spectrum from that. In about five minutes I had my answer. The results showed reflections throughout the waveguide probably from mold but possibly mis-aligned waveguide too. This was how it was supposed to work for training if we’d had all the equipment we needed.

To keep the mold from growing, the waveguides are pressurized with dried air and the air driers have to be changed more or less frequently depending on the humidity. In the tropics that should be at least once a week. The maintenance log showed it had been done twice in 9 months. That meant the waveguides had to be completely dismantled and cleaned. There are about fifty pieces of waveguide in this unit, all very carefully aligned and screwed together. One bit of this high-tech plumbing was a unit that looked something like candelabra crossed with a music staff called a T-R tube. This would be almost impossible to clean and I didn’t have a spare.

Capt. Fiori was not happy when I told him the process might take as much as two weeks. I gave my report to the Lt. Col Stockton and he was even less happy about the situation.

The Col. pushed his cap back on his head and furrowed his brow, and having forgotten for the moment the officer/enlisted chasm said, “Can’t you lean on Col. Suel to speed things up?”

Beging your pardon, sir?

“I know, enlisted men don’t lean on colonels for anything. But he sent you out here. Didn’t he have a plan?” The major’s frustration was bordering on panic.

I didn’t ease the major’s growing unease as I said, “All the colonel knew is that your radar is down and I’m between teaching classes. And it was Shackley, actually who sent me up here. He sort of borrowed me from Col Suel. So Suel allowed me up here on a house call. I’m supposed to figure out what to do.”