RADAR UNIT 10

The COL station (Chain Overseas Low) was the same as the English CHL (Chain Home Low).

I believe that the Pulse Repitition Rate(PRF) was 400 cps. With the transmitter H.T. being 20 KV and tuned for a 4 micro-second pulse width on a monitor oscilloscope. The main storage capacitor was 25 KV. rating and quite lethal if not earthed during manntenence. Earthing was a must every time the transmitter was serviced. No one ever dared to overlook that procedure! The capacitor was coupled to a half wave rectifier and this was the only filtering in the power supply.

The Transmitter was fitted with many foolproof devices and when pressing the button to bring on the HT, it commenced with 1O KV and then wound up to 20 KV. Tuning of the lecher lines was always checked with the view on the monitor oscilloscope.

The Receiver controlled all functions including triggering the transmitter and any other gear which required synchronisation with the CRT displays. I don't know if NZ stations were ever fitted with auxillary gear and display units.

The two tubes for the display of signals were the Height/Range tube and the Plan Position Indicator ("PPI" Tube). The HR tube was calibrated to 100 miles with the first 5 to 10 miles useless on account the Transmitter pulse break through and the PPI was calibrated to 60 miles with a grid map superimposed with the station at the centre.

Mount Egmont was used as a guide for propagation checks. The Transmitter beam was 15 degrees and during normal conditions spread approximately 10-20 miles on the base line with inversion conditions and anomalous propagation there would be anything up to 50 to 60 miles. This would also show up as a big orange blob on the PPI tube which was a long persistance type.
Impedance matching was used with the common switching mode for Transmit and Receive. Spark-gaps, glass, sealed with 2 wire ends like an axial capacitor were tested with a Megger. Over a period the clear glass would become blackened. An indication that there may be leakage within the glass tube.

We had one project for the DSIR (Department of Scientific and Industrial Reasearch). This was each and every hour to keep a record of wind direction, cloud formation, base line length of Mount Egmont, and possibly others for a period of 4 weeks.

Early morning shifts on many occasions were delightful. From the operations hut looking over the valleys and hills to the south and at the break of dawn with the sun rising it was great to see the fog in the valleys slowly disperse and the greenery show up. I was never tired of that view.

We did once have fire on the hillside below the ops hut, and every available man was called upon to help put it out. Even our red headed OC worked as hard as anyone. That was Bill Stott a Canadian corporal and also a ham VE7PZ from vancouver.

Inside a dormitory hut.

The main meal of the day was the evening meal . Invariably there was a choice of meats. Our cook Charlie was quite inovative and we fed well.
Off duty times saw various activities . Mostly arround the country side with long hikes, many times to the bay at the bottom of the hill. A regular was a daily walk to one of the farms at Puponga to collect milk for the unit.

The scanner was mounted on a wooden tower about 20 feet high and consisted of 40 dipole colinear array. The reflector was constructed of steel mesh. The feeder was 300 ohm open wire and a magnetic coupler allowed the RF to be passed through to the rotating array. The aerial was common on transmit and receive. The scanner was turned by a DC motor and rotation speed could be changed by the operators and rotation could be reversed.

Click here to return to front page.

Page up dated 21:51 14/10/02.