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RADAR SYSTEMS STATUS REPORTS
RADAR SYSTEMS STATUS REPORTS
Table of Contents
Table of Contents
Alberta Hail Project 1979:
Radars
The project radar systems are depicted in Figure 5. In view of the success of the previous year's operations, no major modifications were made to the equipment, assistant training, 24-hour shift arrangement, or computing facilities.
Twenty-four hour data logging was repeated again this year, however, the C-band data were logged on a continuous basis while the S-band data were logged simultaneously between 1200 and 2100 hours if there were echos to justify its operation. Dual wave-lengths experiments were therefore undertaken throughout the majority of the season without affecting the normal hail monitoring program.
Test equipment failures and manufacturers' repair delays were such that by early July to the end of the season, rental units, X, C, and S-band signal generators and power meters, were in use throughout the operation.
S-Band
The previous year's transmitter problems continued throughout this year's operations. Both the 20 volt power supply and the local oscillator required replacement, while the pulse package underwent testing, replacement, modification, and finally complete rejection at the end of the season. The complete transmitter has now been returned to the manufacturer.
The S-band elevation and microwave housings were rewired and exposed cabling was enclosed in additional weather-resistant sheathing to improve system reliability. An attempt to calibrate the S-band antenna using a standard target suspended from a small tethered helium-filled dirigible was unsuccessful due to high winds.
The S-band radar operated for a total of 709 hours.
C-Band
Preliminary design and tests of a step scan elevation control for the C-band radar was completed but not installed for the season's operations. However, to allow for dual wavelength experiments, an elevation control circuit was installed that allowed the C-band elevation to be slaved to the S-band elevation control circuitry.
The C-band operated on a 24-hour basis with nightly testing, calibration, and maintenance as necessary. Operation throughout the season was uneventful and the system operated for 1187 hours.
X-Band
The rotary joint was replaced before the season commenced, and no further difficulties were encountered. The system operated for 1000 hours.
Alberta Hail Project 1980
Radar
Operating schedules and facilities were similar to those used in previous years (Fig. 5). However, various technical difficulties limited useful archived radar data to 60 computer tapes. On several occasions, C-band radar data wee archived for twenty-four hour periods. Little dual-wavelength data were archived.
S-Band
The transmitter, returned to the manufacturer after the 1979 field season, was received in the spring of 1980. The manufacturer modified the transmitter to include constant voltage transformers on the magnetron filaments and then evaluated the transmitter's performance to ensure that it met the original specifications.
The transmitter performed well for a short period at the start of the season and then repeated its past history of failures. At the end of the season, after many repair attempts, the pulse package was returned for warranty repair and the magnetron sent to Varian Associates (the original manufacturer) for evaluation.
Additional failures in the antenna evaluation drive circuitry and the main azimuth bearing rendered the S-band systems unserviceable for larger periods of time.
C-Band
The transmitter/receiver performance was enhanced by the installation of an improved passive TR cell whose nominal operating life is in excess of 3000 hours versus the AC power "on-time" life of only 500 hours for the active TR cell.
Due to frost damage to the concrete foundation piers of the radar tower, the piers were banded with steel straps to prevent the tower from collapsing.
At the completion of the summer field program, the pedestal was taken to Edmonton for installation of improved electronics and the tower was removed and repair action on the piers initiated.
X-Band
The new rotary joint, installed in the summer of 1979, failed and was replaced with a unit capable of passing only 2/3 peak power. The low power rotary joint and antenna corrosion prevented using the system at more than half power.
Plans are under way to replace the system with modern designed equipment.
Alberta Hail Project 1981
Radars
As a result of deteriorating facilities, the radar complex was relocated to the north of, and adjacent to, the site of Building 29. This necessitated new tower bases for the C-band and X-band radars as well as a tower extension for the X-band antenna. All radar related electronic equipment was installed into a double wide ATCO enclosure located to the NE of the three (3) radar towers.
The aircraft PPI control facility was reconfigured into a console layout and relocated into Building 38.
The separation of the radar electronics into a radar site and a display center, necessitated the installation of a radar data remoting system. The purchase of a multifibre fibre-optic cable, support electronics, computer I/O port multiplexors, models, and radar data multiplexors allowed for the assembling of a state-of-the-art remoting system which operated well throughout the season. The three project radar receiver systems are depicted in Fig. 5.
S-Band
The evaluation of the magnetron performed by Varian Associates following the 1980 field program proved that the tube had been electronically damaged. A repair order was issued and the repaired tube returned in mid-June. However, following installation and performance evaluation by a team of ASD personnel and Varian experts, it was agreed to shut the system down and await a redesign of the magnetron's support electronics, in particular, the pulse forming network and pulse filament transformer. With support from Varian and EEC, a new PFN and pulse package should be installed in time for the 1982 field program.
Through a subsidiary of a German company in Vancouver, B.C., a new main bearing for the antenna system was obtained. This was installed along with considerable refurbishing of the mechanical drive system. By mid-August, the antenna system was operating and fully controllable from the new radar facility. To complete the system, the old AN/TPRS, 502 S-band Transmitter was successfully reactivated. Thus during the latter part of August and the first part of September, S-band data was collected either singly or in conjunction with C-band data. S-band/C-band antenna slaving was not electronically available.
Recorded S-band data totalled 75.6 hours.
C-Band
This radar system was the main source of radar data throughout the field program. After installing a new magnetron in the month of May, the transmitter/receiver operated without a fault.
The slip ring assembly inside the antenna pedestal suffered a catastrophic failure in mid-July; by using old and used parts. However, the system was partially available within 6 hours. Through refurbishing of used parts, the system was returned to full service within 3 days, and operated without difficulty for the remainder of the field program.
This system, operating on a 24-hour available basis with nightly calibration, totalled 970.5 hours of operation.
X-Band
During the winter months, the X-band antenna was refurbished by the U of A and then sent to NRC, Ottawa, for pattern evaluation and gain measurements. By utilizing a 3 mil mylar face cover, it was possible to reduce the Voltage Standing Wave Ratio to less than 1.5, thus enabling the transmitter to operate into it. Following the rapair of two transponder sets, the total system, operating at half power as a result of low power rotary joint and a high antenna V.S.W.R., operated flawlessly throughout the field program.
The system operated for 367 hours.
Alberta Hail Project 1982
Radars
Operating schedules and facilities were similar to those of the 1981 field program. The C-band radar was available throughout the program while the S-band radar was available for the latter half. In general, the C-band radar provided the normal surveillance data; the S-band radar provided information only during research activities.
S-Band
During the interval between the 1981 field program and the commencement of the 1982 field program, unsuccessful discussions were held with EEC (Enterprise Electronics Corporation) with regard to rebuilding the magnetron modulator. It was therefore decided to undertake the design, construction and testing of a new modulator in house. The newly designed modulator tested satisfactorily and was installed into the transmitter by 25 June. A report of this design will be available shortly.
A lightning strike near the radar facility on 1 August damaged the new modulator and the remote monitor. Repairs to both systems were completed within 7 days. The original double side band, high noise figure receivers were replaced with a set of single side band, low noise figure receivers. These receivers were in place and worked to design specifications throughout the 1982 program. The design is documented in an ASD report, "An S-band low noise receiver" (G. Cardinal, February, 1981).
Between 9 July and 12 September the transmitter was used for 122 hours.
The antenna drive mechanism suffered aging difficulties throughout the summer. The slow speed clutch failed again and was replaced with a modified electronic drive control while the old clutch was returned for an in-depth investigation of its failure. At the close of the season the main drive was dismantled for refurbishing of its gears and bearings.
C-band
A new slip ring assembly could not be delivered in time for the field season commencement, thus old fingers were refurbished with new contacts. The pedestal was thus operational throughout the season.
A new magnetron (LT7156A) was installed in July. The old one (installed in May 1981) had operated for 1700 hours.
The C-band radar, available 24 hours with nightly calibration, totalled 1306 hours of operation.
X-band
The transmitter thyratron failed mid-season; an on-hand spare returned the system to full operation within hours of the failure. Four transponders failed during the season. The failures, coupled with the reduced number of aircraft, occurred over a sufficient period that each seeding aircraft always had a transponder when needed.
The X-band operated for 366 hours.
Alberta Hail Project 1983
Operating schedules and facilities were similar to those of the 1982 field program. The C-band radar was available throughout the program. In general, the C-band radar provided the normal surveillance data; the S-band radar provided information only during research activities. A simplified block diagram of the radar receivers is shown in Fig. 5.
S-Band
Mechanical construction of the IF slip rings caused concern and calibration difficulties throughout the season. The IF slip rings are scheduled for replacement before the 1984 season commences.
On 10 June, a capacitor failure on the new modulator rendered the system inoperable for 7 days. Oil leaks on the modulator housing were an ongoing source of concern until 1 August when a clean solder seal was achieved.
A shunt diode failure on 11 July rendered the system inoperable for one day and resolved the fluctuating RF power level that had been observed closely for a few days prior to the diode failure.
The antennae drive mechanism was unsatisfactorily refurbished by an outside firm. A temporary repair was successfully undertaken by the ARC machine shop and a new drive system was ordered with delivery expected by March of 1984.
Between 20 April and 2 September, the S-band system provided 459 hours of data.
C-Band
A coaxial magnetron and commercial modulator were installed and tested during May. On 9 June, the transmitter/receiver was installed in Red Deer and declared operational even though the modulator was not operating within acceptable engineering specifications. The purpose was to gather valuable statistics on the modulator and then return the modulator to the manufacturer for warranty repair at the end of the season. This was not possible, as by 25 July, internal arcing within the modulator required the coaxial magnetron/modulator package to be removed and the operation continued with the standard magnetron/modulator package.
A new thyratron was installed on 10 July. Even with the changes, the C-band radar system was able to provide normal surveillance throughout the season. Between 9 June and 2 September the system provided 1119 hours of data.
X-Band
The sytem provided 421 hours of data throughout the season. Coverage was maintained with the transmitter operating at half power, a result of the antenna impedance mismatch. A project was undertaken during the summer to investigate the possibility of modifying the waveguide dielectric constant in an attempt to match the antennae characteristic impedance to the waveguide. Fabrication requirements for the project have yet to be completed.
Prior to commencement of the season, one transponder required repair and the mylar antenna cover required replacement.
Alberta Hail Project 1984
Radar/Computers
Operating schedules and facilities were similar to those of the 1983 field program. In general, the C-band radar provided normal 24-hour surveillance data; the S-band radar provided information only during research activities.
During the Month of August all radars were equipped with spark gaps across their respective magnetrons.
S-Band
In April, before the commencement of the 1984 field program, the S-band antenna was lowered to the ground for inspection, to perform a series of antenna microwave measurements, and to install a new worm gear drive assembly.
While the feed horn was within easy reach, the cover plate was given a coating of resin to replace the worn away resin. A reapplication of resin to the feed horn cover appears to be necessary every five years.
Six weeks after installation of the new worm gear drive, an unusual sound commenced, diagnosed as worm gear run out. After consultation with the manufacturer, it was decided to proceed with standard operations and return the worm drive for refurbishing after completion of the field program.
To meet the demands for phase information at lower sensitivities, the S-band phase chassis was redesigned, tested and demonstrated to be capable of providing valid phase data for RF levels of -100 dBm to -30 dBm.
The ATR cells were replaced to complete the refurbishing and the 3-phase, 10-Hp motor control relay system was completely replaced with new updated components.
The azimuth rotary joint failed in June and was repaired with the assistance of the ARC machine shop utilizing commercially available parts to rebuild the internal plumbing and housing. The radar system was again operational 72 hours after failure.
The failure of a synchro transmitter on the polarization control circuitry prevented calibrations during the last week of the field program.
Between 1 May and 1 September, the S-band system provided 490 hours of data.
C-Band
The coaxial magnetron modulator which had failed during the 1983 field program caused considerable concern for the 1984 field program. The complete modulator was redesigned, rebuilt and fully tested with our coaxial magnetron at the manufacturer's plant. The magnetron and its modulator were reinstalled on 17 July and the radar returned to 24 hour surveillance and data recording mode. Calibration once a week (weather permitting) allowed maximum uninterrupted surveillance time for the Alberta Environment hydrology programs that ran simultaneously on the PDP 11/44 computer. Commencing 17 July, C-band data were always recorded whenever S-band data were not being recorded.
The C-band system was in use from 22 June to 17 July with conventional magnetrons. However, because the frequency spectrums from these expired, conventional magnetrons were erratic, no data was recorded. The system was used only for surveillance during this time.
On 8 August, the modulator arced internally and the current monitoring circuit shorted to the modulator's case causing the loss of this minor facility. Additional modulator internal arcing problems commenced on 26 August. With slight adjustments to the transmitter's output power, the end of the field season was reached without a complete modulator failure. The modulator was returned to the manufacturer for repair in September.
The C-band thyratron failed on August 26 and was replaced with a new unit.
Between 22 June and 1 September, the C-band system provided 1065 hours of surveillance.
X-Band
Prior to the field program commencement, one transponder was returned from repair. A second transponder failed in June and was subsequently repaired and returned to service three weeks later. A third transponder was electrically destroyed by a power supply failure in a cloud seeding aircraft. The decision to proceed with repair is still outstanding, due to the high cost.
The refurbishing of the X-band radar antenna has corrected impendance mismatch experience in 1981. The system was run 2 dB below full power because of the low power rating of the present azimuth rotary joint. This rotary joint will be replaced with a high power unit as funds become available.
The passive TR limiter failed on 19 August and was replaced with an old active TR cell. The failure of the TR limiter was exhibited by a high insertion loss. The nominal life of a TR limiter is 1000 hours; the actual life of the installed limiter was 1,463 hours acquired over 4 years.
Between 1 May and 31 August, the X-band system provided 309 hours of data.
Alberta Hail Project 1985
Operating schedules and facilities were similar to those of the 1984 field program. In general, the C-band radar provided normal 24 hour surveillance data, the S-band radar provided information only during research and seeding activities. The x-band radar was in operation at all times when the research or seeder aircraft were airborne.
In the fall of 1984, several components were removed from the radars for repair, overhaul, and replacement. The components included:
a. The S-band slip ring assembly, azimuth rotary joint and worm gear drive;
b. The C-band azimuth and elevation rotary joints and pulse package; and
c. The X-band, azimuth rotary joint and gear drive assembly. Also the X-band receiver/transmitter and the S-band monitor were brought to Edmonton for overhaul and modification.
Prior to the 1985 field operation:
a. The S-band received a new slip ring assembly, new azimuth and elevation rotary joints, new waveguide switches, a rebuilt worm gear assembly, and a zero degree heading marker;
b. The C-band received new azimuth and elevation rotary joints and a new pulse package, and the X-band had a new azimuth rotary joint a a rebuilt drive gear assembly installed, the antenna received a new mylar cover;
c. All three radars were mnodified to allow pressurization of the waveguide assembly;
d. The modified S-band monitor was re-installed onto the 30 m (100 ft) tower and aligned to the S-band radar.
Summer operations
S-Band
Two major failures of the S-band occurred during the 1985 summer season:
a. The waveguide sidewall coupler had severe pressure loss and was removed. A new coupler was ordered to be delivered in three to four weeks. A temporary system was built using the existing waveguide for this short period. The new coupler finally arrived and was installed on October 4, 1985.
b. The high voltage power supply failed on July 22, 1985. The S-band was back on line on July 24, 1985 with a temporary fix.
A new high voltage power supply was installed on July 26, 1985 and the S-band remained healthy for the remainder of the season.
C-Band
This radar operated well this season with only a couple of problems:
a. The inherent, automatic frequency control problem was traced to trim pot failure. These trim pots were replaced and the AFC worked well for the remainder of the season. A new AFC-discriminator control is now in-house and will be installed for the 86 field program.
b. A TR cell and thyratron tube were replaced in the C-band.
X-Band
Only one major component change was required, this being a new thyratron tube.
During the summer months, solar orientation and antenna gain checks as well as calibrated sphere tests, were carried out on both C-band and S-band to determine the accuracy of the antennas.
References
Diebert, R.J. (ed) 1980: Alberta Hail Project field program 1979. Alberta Weather Modification Board, Three Hills, Alberta. Rpt No.11, 106pp. Diebert, R.J. (ed) 1982: Alberta Hail Project field program 1980. Alberta Research Council, Edmonton, Alberta, 113pp. Atmospheric Sciences Department 1981: Alberta Hail Project field program 1981. Alberta Research Council, Edmonton, Alberta, 65pp. Diebert, R.J. (ed) 1982: Alberta Hail Project field program 1982. Alberta Research Council, Edmonton, Alberta, 58pp. Diebert, R.J. (ed) 1983: Alberta Hail Project field program 1983. Alberta Research Council, Edmonton, Alberta, 64pp. Diebert, R.J. (ed) 1984: Alberta Hail Project field program 1984. Alberta Research Council, Edmonton, Alberta, 60pp. Diebert, R.J. (ed) 1985: Alberta Hail Project field program 1985. Alberta Research Council, Edmonton, Alberta, 70pp.
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