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ROC RADAR ENGINEERING

Hardware Engineering, also referred to as Radar Engineering, provides sustaining engineering to the NEXRAD program by continually working day to day issues associated with interference and level two support of operational radar issues. Our long term projects associated with the Service Life Extension Program (SLEP), sustaining engineering, and routine obsolescence help ensure the radars turn tomorrow.

Interference Analysis

There are multiple types of interference that degrade radar data quality ranging from physical blockage to Radio Frequency (RF) interference emanating from external sources.

We will work with a site when they have been notified by an outside entity that a new structure or physical blockage is proposed in the forecast area of the site. We have performed analysis on a Mine Tailings mound being created by a neighboring mining company. We identified the geographic location of the mound and performed an analysis as to how tall the mound would have to become to begin blocking the radar signal. Air traffic control towers, airplane hangers, water towers are the primary man made structures we have performed radar blockage analysis. However, we also provide calculated RF energy levels at the proposed structure location to determine if the transmit energy from the WSR-88D will cause concern for exposure to non-ionizing radiation for personnel or possible bulk cable interference.

As the RF spectrum becomes more crowded, commercial cell, WiFi and radar interference has become more commonplace. If an interference strobe has been identified by WFO personnel, and is persistent, we will conduct an analysis of the interference. We begin with desktop research of the RF sources in the area, working with local site personnel, the most familiar with the neighboring towers and buildings, querying the various RF source databases, and we will generate a list of possible candidates. When possible we will contact owners of the suspect equipment and schedule on-off tests to verify that they are the source. We also work with the various government agencies (NTIA, FCC, DOD, FAA) in resolving the interference. Results of our efforts vary. In some cases we can resolve the issue quickly, a few times the interference resolves itself without explanation. When we are dealing with another government agency or the source can’t be easily identified the resolution can take years.

Radar

We work on all aspects of the radar operational hardware, from the RF generator to the antenna feed horn. The various Service Life Extension Programs (SLEP) (Signal Processor, Transmitter, Antenna/Pedestal, Backup Power) have been designed to reset the clock on the WSR-88D, combining this with our routine Routine Obsolescence efforts we are extending the life of the radar for 20+ years.

Sustaining Engineering

Here are a few examples our our Sustaining Engineering Efforts:

-ECP0815 (Mod Note 216) replaces fiber optic cabling within the 3A15 modulator. This modification replaces existing fiber optic cabling (adequate but not optimal) with larger core fiber-optics maximizing trigger signal transmission improving overall reliability of the modulator and providing a more stable transmitter pulse. In some cases it reduces pulse jitter of the transmit pulse producing a more uniform pulse sequence reducing transmit pulse clutter which improves overall data quality.

-ECP0667 is an engineering effort to remove the phase/shifter – stepper motor assembly from the RF Pallet. We are currently in the initial test phases of the project. One field site, Houston, has received the modification. We have also modified the KCRI system within the ROC testbed. In FY22 we anticipate moving to install the modification in ten operational field sites. If the project proves successful it will reduce overall maintenance associated with RF Pallet and improve transmit pulse stability.

-ECP0861  (Mod Note 206) will soon be sent to the field. This project will install a new Choke Assembly. Once installed the unit will improve DC Servo-Motor performance. We anticipate sending this modification to the field in FY22.

NEXRAD Site Power

The NWS and DoD/AF radar electrical distribution system is a 3‐phase, 4‐wire, 208 VAC, 60 HZ, wye configured system with a 200 Amp service.  Therefore, there is a main site fused disconnect where commercial power enters the site.  The neutral is derived and connected to the system ground at this disconnect.  This is the only point where neutral and ground are connected.  This electrical design is in accordance with Article 250 of the National Electric Code (NEC).  It is important to note that the WSR‐88D system is specifically engineered with this one neutral/ground bond to minimize ground connect loops, thereby stabilizing voltage to improve the WSR‐88D’s system reliability.  There are NO separately derived sources.  Next, the commercial power is connected via the fused disconnect to the Automatic Transfer Switch (ATS).  The ATS is a 3‐pole switch because the neutral and ground must pass unbroken through the switch.  The stand‐by generator, rated at 120/208 VAC, 80 KW, 3‐phase, wye configured, also supplies power to the ATS.  Once again, the generator is not a separately derived source.  Its neutral and ground are not connected.  The ATS is wired for dual output, one output circuit deemed critical and one deemed non‐critical.  The critical output feeds the input to the UPS.  The UPS is a 120/208 VAC, 40 KW, 3‐phase, delta configured, where neutral and ground pass through the unit unHarddisturbed.  Again, the system’s UPS is not a separately derived source.  The output of the UPS is fed to critical electrical and electronic loads in the radar.  The non‐critical side of the ATS feeds directly to the facility where it supports HVAC, lighting, radome heaters and other miscellaneous loads.

EC0843 - National Refresh of NEXRAD Emergency Standby Generators Automatic Transfer Switches and Fuel Tanks. (Mod Note 219) This program is currently replacing all legacy generators, automatic transfer switches, and fuel tanks with new state-of-the-art equipment.  The Generator SLEP program was needed because of parts obsolescence, increased maintenance requirements, and the need to support environmental air quality regulations.

Troubleshooting And Fleet Wide Support

-While maintaining non-IT hardware, located within the RDA compound, we work with ROC electronics technicians, Configuration Management Specialists and Technical Writers to develop troubleshooting guidelines, diagrams and schematics. We travel to field sites for kit proofs, talk with local personnel to determine what else can be done to improve overall reliability and reduce maintenance time.

-We work hand-in-hand with the NWSTC to help ensure training materials are accurate and up to date.

-Weekly to daily discussions with the NRC discussing repair techniques and best practices to ensure parts are repaired to achieve maximum reliability and quality.

-Routinely work the NLSC to ensure shipping materials are optimized to protect NEXRAD components from damage while being stored or in transit.

Routine Obsolescence

At any given time, this department is working multiple components to determine suitable substitutes or methods to repair existing components. At present we are in various stages of qualifying:

  • Manual Davit Hoist
  • Electric Davit Hoist
  • Damper Motors
  • RDA/TPS HVAC Thermostats
  • AME Step Attenuator
  • AME Peltier Assembly
  • AME Chassis