Alberta Hail Project 1979 Alberta Hail Project 1980 Alberta Hail Project 1981 Alberta Hail Project 1982 Alberta Hail Project 1983 Alberta Hail Project 1984 Alberta Hail Project 1985 ReferencesAlberta 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.