performance testing of shipboard electronic systems

GEORGE HARDER, PE & ROBERT A. MARTIN

Performance Testing of Shipboard Electronic Systems

THE AUTHOR

George Harder is an electronics engineer jo i ' Naval Undersea Warfare Center Detachment Noi:folk's Electromagnetic Engineer- ing Bimich located at the Norfolk Shipboard Electronic Systems Evaluation Facility (SESEF) site. He is responsible ,for fleet electromagnetic readiness (FEMR) inspections on board Nuvy ships and pro\,ides computer programming support to SESEF. Mr. Harder has a bachelor of science degree in electrical engineering from the University of Florida and has qualqi'ed for his projession- al engineering license in the state of Virginia.

Robert A. Martin is a supei.visor electronics engineer employed by the Naval Undersea Warfare Center Detachment Norfolk. He ,functions as the branch head ,for the Electromagnetic Engineering 0~i:c.e Mzhich is responsible for the operation of the Norjolk Ship- hoard Electronic Systems Etnluation Facility (SESEF) and rhe Fleet Electi.omugnetic Readiness (FEMR) Program. MI.. Murtin received a hacheloi. of science degree in electrical engineering from the University of Akron.

ABSTRACT

Performance evaluation of shipboard electronic systems en- tails debugging the systems in a laboratory environment, plac- ing them in service and relying on system operators to provide feedback. General testing can be performed a t selected sites by system designers, but each site where equipment is to be installed can offer unique problems. It is impossible to predict all the scenarios. Unique problems are more the rule than the ex- ception when equipment is destined for Navy ships. Ship de- ployments make for difficult logistics when sending test teams to evaluate system failures. So, out of necessity, if newly installed equipment receives the proper inputs and generates the proper outputs, it is accepted and becomes the sailor's respon- sibility to maintain. In cases where documentation is ambigu- ous or incomplete, it is left to the sailor's ingenuity to continue testing and training on equipment. This is generally obtained through computer simulations and back-to-back testing which can provide results for ideal conditions, hut does not take the dynamics of interference into account. Remote site testing is the only way to get a true representation of equipment performance and training problems. Electronic sy4tem operators on board Navy vessels are fortunate, they have help. There exists

an organization available near major naval ports worldwide whose existence is to test electronic systems performance. The testing utilizes electronic systems as they would normally be configured for operations. This organization is the Shipboard Electronic System Evaluation Facility (SESEF).

INTRODUCTION

T h e origins of the Shipboard Electronic System Evaluation Facility (SESEF) date to just after World War 11. During the war, scientific progress came in leaps. This was very true with communications and radar technology. After World War 11, improved electronic equipment was retrofit on older ships and installed on new ships. To evaluate these systems, shipyards were required to establish remote testing sites [I] . The remote sites, SESEFs, would be manned when needed for shipyard trials to measure radiation patterns for the newly installed communication and radar:antennas. At other times the SESEF site would remain unmanned. In the 1970s, Naval Sea Systems Command needed a site for research and development and took over Norfolk SESEF (actually located at Fort Story, Virginia). Norfolk SESEF continued to provide antenna radiation patterns but was also able to provide limit- ed communication checks with Navy ships. By 1980, in re- sponse to requests from commander-in-chief Atlantic Fleet and Board of Inspection and Survey teams, the emphasis of SESEFs was shifted from industrial and post-availability testing to fleet operational testing. Norfolk SESEF and Long Beach SESEF (attached to the Long Beach Naval Shipyard) were tasked to initiate upgrades to provide the fleet with real- time operational electronic systems testing. By 1985, these upgrades enhanced HF, VHF and UHF communications, tactical air control and navigation, identification friend or foe, radar beacon acquisition and electronic countermeasure testing. Other remote testing sites were redesignated as SESEFs and began receiving equipment for additional capabilities. By 1992, there were SESEFs located at Norfolk, Virginia; Charleston, South Carolina; Puget Sound, Washington; Long Beach, California; San Diego, California; Pearl Harbor, Hawaii and Yokuska, Japan (Figure 1). An additional site will soon open at Mayport, Florida.

118 Naval Engineers Journal, May 1993

HARDER PERFORMANCE TESTING OF SHIPBOARD ELECTRONIC SYSTEMS

Lo fig Beach, California

\* San Diego, California

~ 3 Norfolk, Virginia

* Charleston, South Carolin k Mayport, Fiorida

<* P z d Harbor, Hawaii O D

c, ’n

Figure 1. SESEF locations.

PERFORMANCE TESTING

SHIP PERFORMANCE

The SESEFs are located near major U.S. naval bases to allow easy access to the greatest percentage of the fleet. This permits testing lor Navy ships as they transit to and

from the base (Figure 2). The SESEF operators are generally ex-military and have worked the shipboard side of the same circuits they now test. Through past experience and sheer repetition of testing, SESEF operators are familiar with most problems encountered during testing. Through analysis of the signals received from the ship, the SESEF operator can help the ship improve its performance by aid- ing in the correction of equipment problems. Since SESEF operators are familiar with a wide variety of problems, a few minutes coordination could save hours of troubleshooting by the shipboard technician.

A ship that tests with SESEF repeatedly is better able to determine their material readiness under at-sea conditions. For instance, as a ship enters a port that has a SESEF, equipment, such as tactical air control and navigation and identification friend or foe systems, thgt may not have been used regularly during the transit, or equipment whose performance is suspect, can be activated and tested. Results will determine whether equipment needs repair or not, thereby improving equipment reliability and reducing unexpected downtime. Alternately, equipment that appears to be operating correctly, such as communications gear, may have low carrier suppression or be generating broadband noise. These problems are difficult to detect on board ship but are easily seen on SESEF’s spectrum analyzers. If a problem exists, SESEF will inform the ship on the circuit. Often, SESEF will remain on the circuit and aid the crew in troubleshooting equipment.

It has always been SESEF’s policy to make the testing as easy as possible for the ship 121. For instance, a ship can quickly check out equipment by contacting the SESEF on their primary guard frequency or via telephone. The ship will activate their tactical air control and navigation equipment and pass the channel it is operating on to SESEF. The SESEF will activate their identification friend or foe

Figure 2. CG-47 USS Ticonderoga.

Naval Engineers Journal, May 1993 119

PERFORMANCE TESTING OF SHIPBOARD ELECTRONIC SYSTEMS HARDER

transponder and pass the codes to the ship via secure communications. The ship can then test its interrogators. After the ship has completed checking its interrogators it can activate its transponder and have it checked by the SESEF. In the mean time, the SESEF will test the transmit and receive capabilities of the ship’s HF, VHF and UHF communications as well as compile a few minutes worth of tactical air control and navigation parameters. If there are no equipment problems on board the ship, the entire process will take only a few minutes. During this evolution the ship transits near the SESEF and is not required to perform any special course patterns.

SYSTEM TESTS

Besides performing electronic testing with the fleet, Nor- folk SESEF is tasked with seeking methods of improving ship’s performance by improving testing capabilities. As the flagship SESEF, new equipment or procedures are first developed at Norfolk SESEF before being incorporated at the other SESEF sites. Improvements to electronic systems testing have included land based tactical air control and navigation equipment certifications, communications testing, computer enhanced antenna radiation patterns, radar scan analysis and patterns, identification friend or foe quick- looks, Link-1 1 and Link-4 testing, direction finding calibrations and improved electronic countermeasures testing.

Tuctical Air Control and Navigation

The Tactical Air Control and Navigation System is a radio air-navigation system which provides an aircraft with distance and bearing information from a ship. The radio signal also contains an identification signal which tells the pilot which beacon is being received. The distance measuring concept used by tactical air control and navigation equipment is an outgrowth of radar range finding equipment where distance is determined by measuring the round-trip travel time of pulsed radio frequency signals. Shipboard tactical air control and navigation equipment generates artifi- cial replies rather than relying on reflections from airborne radars. An aircraft will generate a pulse-pair signal that is received by the shipboard Tactical Air Control and Naviga- tion System. This pulse-pair signal is received by the shipboard equipment and after a 50 psec delay, the shipboard transponder generates a pulse-pair reply. The round-trip time, minus the 50 psec delay, is converted to distance by the aircraft equipment. Using pulse-pairs instead of single pulses helps eliminate interference from false signals. Since the tactical air control and navigation equipment will only pass pulse-pairs with the proper spacing between pulses, reliability of results is increased.

The shipboard Tactical Air Control and Navigation Sys- tem needs only to respond to aircraft interrogations to supply distance data. This, however, would mean that the number of replies f rom the shipboard equipment would constantly be changing as a result of the number of aircraft with interrogators. To maintain some stability, the shipboard transponder tries to sustain an average power supply to the antenna over time. To accomplish this, the receiver has con-

trol over the squitter, which are extra transmitted pulse-pairs known as noise-generated pulse-pairs. The tactical air control and navigation transponder sends a total of 2700 interro- gation and noise-generated pulse-pairs per second. If there are only a few aircraft interrogations being received, the squitter rate will increase and add extra pulse-pairs until the average output power is obtained. If there are more aircraft interrogations, the squitter rate decreases to again maintain the average output power.

More than 2700 pulse-pairs per second indicates a high squitter rate. This means more pulse-pairs are being transmitted which translates to higher average power to the Tac- tical Air Control and Navigation System antenna. Over- driving equipment decreases reliability by provoking premature failure of power sensitive components. A low squitter rate, on the other hand, will offset the strength of the pulse-pairs which directly affects the bearing information an aircraft receives.

While the timing of the pulse-pairs provides distance information, amplitude modulation of the pulse-pairs provides bearing information. The strength of the pulse-pairs is modulated at 15 Hz. A reference burst signal is sent when the pulse strength is at its maximum and pointing due east. The aircraft receives bearing information by comparing the phase relationship of the 15-Hz signal with this main reference burst signal generated by the shipboard transponder. To improve bearing accuracy, a 135-Hz signal is superin- posed on the 15-Hz signal. It has an auxiliary reference burst signal to permit translation of the phase relationship into bearing information. When the average output power is reduced by a low squitter rate, the modulation of the pulse- pairs becomes unstable. Ambiguity arises as the peak-to- peak power of the pulse strengths decreases. The reduction of amplitude of the 135-Hz and 15-Hz signals indicates in- creasing bearing errors.

Tactical air control and navigation equipment is designed to display only bearing and distance information, but not the strength or accuracy of the signals. At SESEF sites, a radio beacon test set is used to monitor the ship’s identification signal, squitter rate, main and auxiliary reference bursts. A digital storage oscilloscope is attached to the test set to observe the pulse shapes. Improper pulse shapes are an indica- tion of impending failure and early detection and correction will reduce Tactical Air Control and Navigation System downtime. To determine the alignment of the 15-Hz and 135-Hz reference bursts, a surface search radar tracks the ship and supplies range and bearing information.

Certifications generally require an aircraft to circle the ship and record tactical air control and navigation equipment parameters [3],[4]. With Department of Defense’s ef- forts to reduce costs, SESEF’s easy access by the fleet and ready availability make it a natural alternative for tactical air control and navigation equipment certifications. Naval Sea Systems Command, therefore, tasked SESEF to certify Tac- tical .Air Control and Navigation Systems. As a side benefit, SESEFs are able to provide ships with a “quick look” test to see if their equipment was functioning correctly. As the ship transits near a SESEF, it could activate its tactical air control and navigation equipment and verify that its parameters were correct. For a complete certification, the ship rotates



near one of the SESEF buoys in the SESEF operations area (Figure 3). The Tactical Air Control and Navigation System parameters are compared to the surface search radar providing range and bearing. The Tactical Air Control and Naviga- tion System equipment’s range and bearing are compared and the deviation is recorded. Upon completion of a 360 degree turn, the test is complete and the ship can continue with its mission. The entire evolution takes only thirty minutes.

Communications

Today, satellite communication is the most popular method of sending traffic to and from ships. In the past, long distant communications between ships and shore were possible using the HF (High-Frequency-2 Mhz to 30 Mhz) band of frequencies. In time of hostilities, it has always been anticipated that satellite communications will be interrupted. Therefore, Navy ships are required to test regularly to maintain their proficiency in HF communications.

An HF transmitter has several different modes of operations for different applications. Upper and lower sideband (USB/LSB) communications make two-way communications possible using only one frequency by modulating one signal above the carrier frequency (USB) and modulating the other signal below the carrier frequency (LSB). Ampli- tude modulation (AM) can be used for drift-free voice communications by using only USB modulation and injecting the carrier frequency for the receiving station to lock on to. Continuous wave (CW) communications is used to send Morse code by activating the carrier frequency for a short duration to represent a “dit” and for a long duration to represent a “dash.” The most commonly used mode of operation is frequency shift keying (FSK) to send binary encoded messages using one frequency for the mark (binary 0) and another frequency for the space (binary 1 ) .

It is difficult for a ship to evaluate its own transmissions. There are test points and meter readings to ensure the transmitter is sending out a signal, but there is no way to guarantee the quality of the signal leaving the ship. Ship to ship testing helps determine if a signal is being transmitted, but again, there is no guarantee of quality. SESEFs are able to test the quality of a ship’s HF system by using a spectrum analyzer to monitor testing.

During HF testing, SESEF first checks USB and LSB communications independently for opposite sideband suppression. If the voice signal can be heard on the opposite sideband, the transmitter signal is over-modulated. This “splattering” over to the other sideband indicates too much power is being sent through the sideband module which, over time, causes premature module failure. More directly, the over-modulation will increase noise interference when both sidebands are used simultaneously. HF amplitude modulation (AM) is simply an USB transmission with the carrier superimposed. Here again, over modulation can be detected by measuring the difference in power between the carrier and the peak modulation. Ideally, the modulated signal should be even with the carrier, however. a modulated signal no greater than 5 db less than the carrier is acceptable. The binary encoded messages transmitted using frequency shift keying (FSK) rely on the mark (binary 0) being sent at

Chesapeake Bay

\

Atlantic Ocean

Figure 3. Norfolk SESEF.

2425 Hz above the carrier frequency and the space (binary 1) being sent at 1575 Hz above the carrier with the carrier being suppressed. If the carrier is not suppressed, power is taken away from the mark and space. One station testing with another may not notice if the carrier is suppressed or if the mark and space are on frequency. SESEFs use the spectrum analyzer to observe the carrier and a frequency counter to ensure the mark and space are within specifications. Dur- ing continuous wave (CW) operations, computers can be equipped to read the length of time the carrier is “on” and interpret the lengths of times as “dits” or “dashes.” A problem that can occur to the CW module is ramping of the CW signal. Ramping is a capacitive effect on the pulse signal where the rise time of the pulse is slowed. This has the effect of reducing the difference between the “dits” and “dashes” causing an increase in errors. The signal can be best evaluated using the spectrum analyzer with the frequency span set to 0 Hz. In all cases of HF testing, the availability of proper test equipment is the best way to ensure the transmitters are operating properly.

Antenna Radiation Patterns

Communication antenna radiation patterns provide tactical assistance in establishing communications with friendly units and reducing interception of signals by opposing units. The strength of signals from antennas is usually not uniform around the ship. Antenna design and placement affects signal field strength. Line-of-sight and satellite communications are plagued by blockages from the ship’s superstruc- ture. To eliminate this, redundant antennas are located around the ship to ensure 360 degree coverage. These antennas are placed to overlap one another, however, blind zones can still occur. Shipboard detection of blind zones is virtual- ly impossible. Antenna radiation patterns can easily identify these blind zones when the ship radiates its beam directly at the SESEF site and the ship rotates 360 degrees. In addition


PERFORMANCE TESTING OF SHIPBOARD ELECTRONIC SYSTEMS I-IAKUER

to blind zones of the antennas, antenna radiation patterns also identify frequency ranges where transmitters may not be operating properly. Antenna radiation patterns require tuning equipment at the fringes of the frequency range which are not normally used. This often shows problems with transmitters at frequencies not nornially used.

In the past, communication antenna radiation patterns required that SESEF receivers be physically tuned. Once tuned, ship’s heading would be passed over a voice network. SESEF operators would manually “crank” circular charts while ink pens would plot the power of received signals. Now, antenna radiation pattern computers control automated test equipment spectrum analyzers which are tuned to prede- termined frequencies. An interface, installed between the ship’s gyro-compass and transmitter, transmits ship’s heading directly to the SESEF computer. The computer also pro- cesses incoming antenna radiation signals and provides visual representation of signal strength on a computer monitor. Multiple communication frequency reception is possible since communication signals broadcast a continuous wave which can be sampled every few milliseconds with no sacrifice in signal quality. Once the ship is transmit- ting all signals, the SESEF operator engages the computer to begin recording. The information is recorded digitally with a visual display on the computer monitor. After the ship has completed the required 360 degree circle, the computer automatically stops recording and informs the operator that the run is complete. Upon acceptance of the run by the operator, the computer will tune the spectrum analyzers to the next set of frequencies.

One important aspect of SESEF radar scan analyses and patterns is to help determine if fire-control radars are causing radiation hazards to personnel. Radiation cutouts are ei- ther physical or software restraints imposed on radars to pre- vent radiation into manned areas. Radar scan analyses and patterns verify that cutouts restrain the radars properly. I n addition, radar scan analyses and patterns also determine whether radar signals are being retlected into manned areas or if there is side-lobe radiation radiating into a manned area.

Equipment specifications impose limitations on radar beam widths and side-lobe energy levels. Ideally, radars should be able to direct all their energy in a narrow beam in one desired direction. In reality, energy is lost due to spread- ing of the beam and in side-lobe transmissions. Here again. i t is difficult for the ship to measure beam width and side lobe attenuation. Radar scan analyses and patterns verify that the beain widths are within design specifications and that the main side lobes are properly attenuated to reduce energy usage and hazards to personnel.

At most SESEFs, radar scan analyses and patterns still require SESEF operators to manually “crank” circular charts. A new development has been to modify the coiiiniunicatioil antenna radiation pattern computers to receive radar signals up to 22 GHz. Unfortunately. rotating radars have ii high pulse repetition frequency (PRF) which prccludes thetit from being sampled periodically with other systems at the

same time. Synchronizing the SESEF receiver’s scan-on period with the shipboard radar’s scan-on period is not possible at this time. Only constant sampling of the radar signal will ensure accurate results. Still, accuracy of the power density patterns is improved by removing manual “crank- ing” by the operators. This implementation will souti he at all SESEFs.

Ident$cation Friend 01‘ Foe

Identification Friend or Foe Systems, like Tactical Air Control and Navigation Systems, will send out information when interrogated. Shipboard and aircraft Identification Friend or Foe Systems can pass up to five different code messages. Modes 1 , 2 and 4 are for military use only and modes 3 and C are for both military and civil use. Mode 1 is a two digit octal code and mode 3 is a four digit octal code that can be programmed by the ship, submarine or aircralt. Mode 3 is intended to be used for such purposes as personal identification, flight leader identification, or even as a navi- gational aid. Commercial and military airports use mode 3 to track aircraft during take off and landing. ?‘tie mode 3 codes are assigned by the flight controllers for quick refel-- ence. All aircraft taking off and landing are reyuircd to transmit mode 3. Mode 2 is also a four digir ol-tal ~ . o i l e h i t i i is preprogrammed and used as the unit‘:, identificaiioii. .411 legitimate users of mode 2 are listed 151 and can 1~ ideiiti- fied by other military units. Mode 4 i h a cryptci-se~ured mode used to quickly identify friendly units. Mode C is an automatic altitude indicator whenever the aircrdft is in1ei-m- gated. Each switch uses three bits to indicate a valuc he- tween 0 and 7. Dirt on a switch contact can srnd a differcnt code than indicated. Faulty codes are not as i:ornniun with the surface fleet if they use their identification friend oi- ftre equipment often. But, faulty codes havc heeii a rcoccuii ing problem for submarines that do not use their identification friend or foe equipment often. Subnrarines ai-e now u>i i ig

SESEFs to provide a “quick look” at their Identificatioii Friend or Foe System output as they transit out to sea and the problem is being seen less by SESEF opcrators.

Link-I I is a communications link to c.xchange digitizec i n form at ion bet w ee ti a i rc r a f t , s u bin a I i i t e . s ti i plw a rd L I I I i

1 and - ba se d tactic a 1 data s y s t e ni s . T h c‘ i n to rni ;i t I o I i 11-0 n radars and sonars is processed i n the N;tviil Tactical Da[i System (NTDS) computers for transmission to the u~hei members i n the link. The link operates i n a roll c;ill riicide with a net control station coiltrolling the order in which i l i t

participating units are polled. When callsd. each u n i t t i . i i I n

niits its information. T h e remainder of the time i t is rccc’iv ing information from other members o t the iici.

With the instalkition o f crypto ecpipnienl. SESEF?, wil l i n k with ships and become active mc.niber\ i n t he iiet

SESEF can act as the net control station o i - 3 parti(:ipirini unit . In cither case. SESEF can iiionitor c x h i i n i l ‘ b trails missions. Each transmission is coinpow1 o ! a pmirthic- used by the receiving station 1 0 “fr;imc i i p “ : phase rti‘ei- ence-the first frame of the riic\>agc: contiol coiie-a ‘,tar



code to precede the data message and a stop code to follow the data message; and finally, the data message frames. At the same time, SESEF can look at the link signal parameters. Signals from a ship may be weak, causing problems for the rest of the units of the net. For example, because of noise or poor preambles, a participating unit can fail to rec- ognize a start code and lose an entire transmission. Or, if a recognizable stop code is not sent, the unit will process noise until their terminals time out. The noise will be converted to data and pass garbage to the computer. SESEFs, for instance, can monitor transmissions and ensure the preamble has the appropriate two-tone signal and that five preamble frames precede each phase reference. Ensuring correct link signal parameters ensures the ship will be able to link with other ships.

Link-4 is a digital two-way RF data link between aircraft and a shipboard control station. This link is established for exchanging target position, commands, orders, responses, emergency data and track status information. Currently, aircraft availability and cost precludes shipboard testing of Link-4 capabilities. Upgrades currently being installed will allow SESEF to emulate up to ten aircraft. Again, SESEF will be able to monitor the signal parameters as well as link with the ship.

Direction Finding

Calibration of shipboard direction finding equipment is periodically required by ships. These tests require certain frequencies be broadcast from a known location. This will enable the ships to collect sufficient bearing versus frequency data to improve accuracy of direction finding equipment. SESEFs are provided with authorized test frequencies with which they create an event schedule to minimize the length of time a ship will be required to remain on the SESEF range. When all the signals are energized, the ship will cotn- mence a 360-degree circle to collect direction finding data. Once they have completed a circle, they request that SESEF tune to the next set of frequencies. SESEF operators must manually tune each coupler. With the addition of the automated test equipment, the computers determine frequency and antenna compatibility. During the actual direction finding, the computers automatically tune the couplers for each run. This has reduced the number of SESEF personnel required for direction finding calibrations from three down to one.

Electronic Countermeasures

Currently, a prototype electronic countermeasures testing unit is being evaluated and fine tuned at Norfolk SESEF. The current electronic countermeasures test unit gives little more than a pass/fail judgment of the electronic warfare system‘s jamming effecti-ieness [6],[7]. The prototype equipment allows a waveform analysis of the electronic warfare jamming signals to provide ships, with marginally passing jamming effectiveness, a better analysis of their signals. This will give the ship the ability to correct equipment problems before they become serious and costly.

Upcoming developments at SESEF include installation of

a central computer which will allow all SESEFs and selected commands access to ship’s testing information, technical data, administrative information, suggestions and com- plaints. All ship’s testing information will be maintained in a central database to provide SESEFs with previous test results for comparison to current testing. In addition, each SESEF will also have access to a corporate memory of equipment symptoms and possible fixes to aid the ship in troubleshooting. All this information will also be available for use by squadron commanders to monitor ship’s readiness.

AVAILABILITY

Besides providing direct operational support for the fleet, SESEFs are available for use by design engineers of electronic systems and their designated contractor representa- tives to check the validity of their design models and verify that test results conform to design specifications. Regardless of how well a system has been designed and tested in the laboratory, there are always problems that are encountered when installed on board a ship. The dynamics involved with shipboard electronic equipment revolve around eleclromag- netic interference from shipboard power supplies and other electronic equipment 181. No laboratory can duplicate the variety of signals from such sources as transmitters, antennas and generators. These signals, individually and in tan- dem, adversely affect the performance of newly installed equipment. On-board testing, with a remote site, can furnish the most complete picture of system efficiency.

SESEF supports functions that are related to electronic system testing from shipyards and Navy mobile technical units. Naval Sea Systems Command has utilized SESEF’s communications to coordinate assistance with ships for signal parameter analysis and for field evaluation of prototype radios. The Joint Electronic Warfare Center has used SESEF sites to evaluate jamming and interception of the Joint Tacti- cal Information Distribution System which is a coordinated effort of all the branches of the armed forces to link all tactical information together during combat situations. The Naval Surface Warfare Center Dalgren has used SESEFs in developing their Waveform Recording and Playback System which records ship’s radar emissions for use during simulations where a ship is to operate in the same electromagnetic “clutter” that it would experience during actual combat operations. The Naval Air Systems Command has asked SESEF to collect power levels of tactical air control and navigation antennas which are to be evaluated for lowering output power while maintaining a tactical area of coverage. The power reduction will also aid in reducing electromagnetic interference to other equipment.

SESEFs also provide a vital support link for Board of In- spection and Survey teams during electronic system testing for acceptance trials, final contract trials and underway material inspections. The role of the Board of Inspection and Survey is to inspect every ship every three years to determine operational readiness and ensure all equipment is oper- ated and maintained properly. Up to sixty officers and con- tractors descend on a ship for a week to inspect all aspects of the ship. The test procedures followed by Board of In-


PERFORMANCE TESTING OF SHIPBOARD ELECTRONIC SYSTEMS HARDER

spection and Survey during ahipboard visits conform to the equipment standards. During the inspection of electronic warfare and communications equipment, the Board of In- spection and Survey relies on nearby SESEFs to provide the partner testing for HF, VHF and UHF communications, in both plain and cipher tnodes, Tactical Air Control and Navi- gation and Identification Friend and Foe Systems. Results are evaluated by the SESEFs and then provided to the Board ~f Inspection arid Survey to become part of their final re- port. In additirw, since SESEFs are the only organizations

m antenna radiation patterns, Board of In- yxction and S~trvry enxures the ship's latest antenna radia-- tion p l t ems :~:ci-e rendcrcd by a SESEF. These inspections help determine a ship's capability to perforni its missions. The Board of Inspection and Survey recommends ships tesi frequently witli SESEFs to improve performance. identify equipment and training problems m d to generally maintairi optimum mission readiness.

SUMMARY

Testing is easily coordinated over the phone or cornmuni- cations net and the "one-stop-shopping" for electronic systems testing reduces the steaming tinie a ship normally re- quires when these capabilities were not available in oric location. SESEFs provide immediate feedback to the unit of the operational condition of their systems. Early identifica- ii1.m of potential problems can reduce equipment down time, nrimber of casualty reportx auci requests for ourside techni- ciil assistance. Often, SESEF personnel provide technical evduations of the received signals and aid shipboard techni- cians with troubleshooting.

So far, testing 'Tactical Air Control and Navigation equipment with SESEFs verses an aircmft has sharply dropped the testing time and cost. Certification with a Federal Avia- t ion Administration (FAA) approvcd aircraft costs the ship $10,000. There is no direct cost ICP the ship for Tactical Air Control and Navigation System eyuipment certifications by SESEF since this is already part of SESEF's operating budget, For instance, Norfolk SESEF performed 64 certifications i n fiscal year 1992. This would come to $640,000 it thesc certific.ations were accomplished by aircraft. The fiscal y a . : ~ 1992 opeilting budget for Norfolk SESEF was

$300,000. This equates to $340,000 in saving:, of the test and evaluation budget from just one SESEF i n one year. In addition, SESEFs provide electronic warfare, communications, search radars and avionics equipment testing.

SESEF test records show the addition of the computer for antenna radiation patterns, radar scan analysis and pakrcrns and direction finding calibrations has reduced the length ot time a ship is required to remain on-staiion. With a simuiia- neous display of all signals and removal of mechanical signal recording, the confidence of accurate test results is increased. The amount of time wasted, in tuning rcccivcrs, replacing plotting pens and papers. ?krwiian ing each receiver and repeating runs due to reduced. In-house records show a reductio percent, over the last three years, in the amount of time a ship is required to operate on the SESEF range.

SESEF managers anticipate further cost savings a:, other new systems are further developed by SESEF criginecrs. In these times of defense budget cuts, SESEF has been leading the way in improving the value of the dollar for the fleet by reducing the fleet's test and evaluation costs.

REFERENCES

1 ?4 Naval Engineers Journal, May 1993

performance testing of shipboard electronic systems

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