WF44-Observer memories

Scrambled eggs at four AM.
Night shifts are dreary. You need to do something to keep yourself awake. One dark dry season morning at Darwin in the late Seventies I was on duty at the Radio Aids Building. The procedure was to do the 17Z balloon flight then do a quick weather watch before shutting the radar down until the 23Z flight.

This morning a flight of F111s had taken off to play games down the track. I spotted their radar echoes over Katherine as I did the post-balloon flight weather watch. Having nothing to do, as I had made gas, completed the monthly records and the like, I decided to see how well the old 44 could track an aircraft or two. I switched from WW to WF and located the flight of F111s and hit auto-track. The radar tracked one of the fighters for several minutes when the display erupted in a mess of clutter. Square waves, saw-tooth waves and other interesting patterns. The WF44 has a nice little 4R function that allows the operator to track a target through clutter. It also has a 'steer' control that the operator can use to track moving targets by setting rates of change in azimuth, elevation and range through a ball and roller control. I switched to 4R and to STEER and was merrily tracking the real echo of the fighter through all the clutter that was obviously being generated by one of the jet's electronic counter measures (ECM) units. After several minutes all the jets headed for ground and I lost them in ground clutter. Some ten or so minutes later I heard them land.

A little after sunrise a RAF Captain rolled up asking about what kind of radar we had. I told him about the WF44. I told him it was very good at tracking aircraft and that I had locked onto the flight of F111s over Katherine that morning. I also mentioned that they tried awfully hard to fool the auto-track system but that one could keep tracking quite nicely in steer mode. He quickly muttered thank you and headed off back to the F111 parking area.

Through the theodolite up on the observation deck I could see that they had the ECM pod in the tail of one of the F111s open and technicians working on it. I guess the Captain told them not to look for any faults.(1)

It was a dark and stormy night.
Well it was! December 24 1974, Darwin. Cyclone Tracy preparing for final approach to Darwin Airport- Straight in along runway 11. In those days Darwin had a WF44 wind find (WF) and weather watch (WW) radar. I was in the city office, having driven into work with my family at around 0030CST after the power was shut down when the BIG power lines feeding the northern suburbs gave way along Bagot Road.

I think it was Vin Shuey who was on at the radar. He did a sterling job sending in Polaroid pix of the PPI (Plan Position Indicator) over the BizFax. The met on duty was busily plotting the centres on a big map as the cyclone got closer and closer. A few hours before the eye hit, the old WF44 went off air. There appeared to be a trigger pulse but no return echo. We all thought that a lump of roofing iron may have wrapped itself around the waveguide feed to the dish, thus blocking the transmitter pulses and any echoes. After a while the radar started to work properly again. Vin was able to take a picture of the PPI when the eye was directly over the station, then the emergency generators were blown away and the radar lost all power.

I recall Vin saying that the elevation would change by several degrees as the dish rotated and the wind loaded up the front then the back of the dish. Considering the gargantuan yoke and gearboxes in a WF44 pedestal, it must have been huge wind loadings on the old 44's dish. (1)

Indonesian TV
This has nothing to do with Indonesian TV, except that when there are strong surface inversions at night in the Dry in the Top End a couple of interesting things happen to radio signals. One being that you can receive Indonesian TV programs in Darwin. On these nights the inversion traps radio signals between the lower atmosphere and the surface. The radar signals are also trapped and occasionally you will get some unusual echoes on the WF44 radar at maximum range. These echoes appear to the north-west. It turns out that these echoes are the 'second-pulse' returns from the island of Timor. The radar transmits a signal then waits for the return echoes. Another pulse is transmitted and because of the good transmission of signals, the previous pulses echoes are received and are strong enough to be displayed.(1)

(1) Alex Kariko - Nov 20021 (private communications)

Elevation meter Photo showing PE's Iso-echo Unit