 |
| 090202-N-N1809-1002 SAN DIEGO (Feb. 2, 2009) A close-up of a model of USS Gerald Ford (CVN 78) at the Antenna Model Range at Naval Information Warfare Center (NIWC) Pacific in San Diego, Feb. 2, 2009, shows a miniature satellite dish, just one detail on a model ship consisting of tiny antennas, satellite dishes, add-on compartments, and anything solid that could affect high-frequency radio communications. (U.S. Navy courtesy photo) |
 |
| Looking North along Point Loma toward NIWC |
Meet the Navy’s Only Model Ship Builder:
 |
| 240222-N-ZB499-1021 SAN DIEGO (Feb. 22, 2024) From left, Fred Blas, Bob O’Neill, Jun Peralta, modelers retired from Naval Information Warfare Center (NIWC) Pacific, and Ben Wong, modeler at NIWC Pacific, pose behind a brass model of USS Arleigh Burke (DDG 51) in the ship model shop at NIWC Pacific in San Diego, Feb. 22, 2024. Among the four of them, Wong and his predecessors have ruled the Center’s ship model shop for half a century, where they’ve built dozens of brass model ships used for validating antenna configurations on real Navy ships 48 times the models’ size before any metal is cut in the shipyard. (U.S. Navy photo by Aaron Lebsack) |
Ben Wong probably won’t say much because he works alone. You might hear radio station Magic 92.5; “Groove Tonight” by Earth, Wind & Fire plays. With the 50-year-old, solid-steel metalworking machines, framed film prints on the walls, and relative lack of screens, it’s one more detail giving the hazy impression you’re not in 2024 anymore.
Trace the moment back a little and you’ll find the work in that shop looks much as it did when Wong first joined in 2008 as an engineering technician after working as a machinist for the San Diego Department of Public Works. In its simplest terms, his job is to build model ships to sit under the arch up the hill so other engineers can test its antennas before they’re installed on a real ship 48 times the model’s size. In broader terms, it’s to save the Navy time, money, and to perfect high-frequency radio communications on its ships.
Wong fields questions in the form of digital blueprints: Here’s how we want to place the antennas, will it work? And he builds his part in the answer with wood, brass — malleable, rust-resistant, and easy to clean — and tiny antennas you could hold between your thumb and index finger. Antenna placement, surrounding add-on compartments, and anything solid can affect how an antenna receives radio waves, which means part of Wong’s job is building by hand miniature fixtures like satellite dishes, delicate enough to top a dollhouse.
Except the dollhouse is a ship, and it’s the key to a math problem instead of a toy: What’s the fewest number of antennas, and where should we put them, for full high-frequency communications coverage?
It may be the Navy’s singular question still answered by hand measuring, hand sanding, with wood and brass and a unique sort of professional labor enduring within these walls yet fading to history otherwise. Here the skill of solving Navy problems more with hands than computers is alive and raucous, spanning generations of model makers who dedicated their careers to this shop.
“This job requires an open imagination,” Wong said, “because there’s never a right way or wrong way of machining. Everybody machines differently. I’ve learned a lot from other journeymen,” some of whom we’ll meet soon. “That’s where I’ve learned a lot of my skills, just kind of talking to people and working together.”
Keep tracing backwards and you’ll meet first Jun Peralta, who shared the shop with Wong before retiring in 2018; then Bob O’Neill, who worked in the shop 1986 to 2008; then Fred Blas, 1976 to 2002. O’Neill and Blas saw the model range’s transformation from a zenith arch to a composite-material tripod arch in the 1990s, right around the time people first said computers would make model makers jobless — a prediction each subsequent modeler proved wrong.
 |
| 090202-N-N1809-1001 SAN DIEGO (Feb. 2, 2009) From left, Ben Wong, modeler at Naval Information Warfare Center (NIWC) Pacific, and Jun Peralta, modeler retired from NIWC Pacific, pose next to a model of USS Gerald Ford (CVN 78) at the Antenna Model Range at NIWC Pacific in San Diego, Feb. 2, 2009. With Bob O’Neill, another retired modeler, Wong and Peralta built the Gerald Ford model, just one of the many models they’ve built for use in validating antenna configurations on real Navy ships 48 times the models’ size. (U.S. Navy courtesy photo) |
Now they’re all back in this shop, pulling a sort of reverse interview: “You want to know the three most common questions we get from people who come in here?” O’Neill asks, first firing off one, admittedly, on my list.
I cross off “Do you build models for fun at home?” — they don’t. “Do you go home and write?” they ask. “That’s like asking an auto mechanic if he goes home and works on cars,” Blas says. I say sometimes, but come clean that I don’t go home and write about antennas for fun.
“Do they float?” They don’t — their bottoms are hollowed out for wiring. And, “They pay you to do this?” Hearing them talk about it, it’s almost a valid question. For the years their tenures overlap, going to work meant enjoying the satisfaction of the same hands-on craftsmanship hobbyists do at home for free, all among friends who’d prove to be lifelong.
O’Neill and Blas, for instance, were coworkers first, then neighbors starting in the late 1980s. They carpooled to this interview, which turns out less like an interview and more like a reunion. I ask Wong what kind of music he plays in the shop and he mentions Kool & the Gang’s “Cherish,” apt for the moment.
I ask Wong what he was doing last time he was happy at work, and he says he’s happy any time a model build helps solve someone’s problem. “Especially if it’s a rush job and they need it right away — getting it built well and in time without any snags brings me satisfaction. Like, ‘I did the job right. He met his deadline because I helped out.’”
I ask why brass models work better than digital ones and they tell me to ask Jodi McGee, head of the Electromagnetics and Advanced Technology division. She says, “Since I started at the Center almost 30 years ago, people have been saying that computational modeling should be able to replace brass modeling ‘in a few years.’ Periodically, our engineers check in on the progress of computational modeling for high frequency. It’s getting closer than ever, but there are still a few very challenging problems that prevent us from giving up brass models.”
NIWC Pacific’s design engineers do use computational electromagnetic modeling for predicting antenna performance in some situations, but it’s still a challenge in the two megahertz to 30 MHz band — classified high frequency, but a relatively low-frequency band with long signal wavelengths between 10 meters and 150 meters long. Because the wavelengths are so long, amounting to a significant proportion of the vessel’s size, the entire ship functions as one big antenna, a synergy of surface currents flowing over its complex shape. If that synergy isn’t accounted for, it can affect operational performance.
For now, brass modeling just predicts that operational performance better, capturing both the sum effect of the antenna network’s parts, and the minute details of its more complicated parts.
A fan antenna, for instance, could have six wires fanning out and running down the deck topside on each side of the mast. If you know the electrical impedance of the fan antenna — how resistant or reactant it will be to current running through it — before computer modeling, you can tweak the computer model to account for it, sure. But the point of modeling antenna configurations on Navy ships is to prove effectiveness before spending the time and money to build the antenna — or even the ship. And so brass modeling still wins.
The brass models are also cost effective. “We’ll build a ship model that can be reused over the life of that ship class, which may be 30 years or more,” McGee said. “Our Nimitz-class aircraft carrier model was built more than 50 years ago and is still in use.”
And when ship classes undergo modernization, modelers can validate planned changes won’t impede communications before any metal is cut in the shipyard. Effective models can prevent costly rework on actual ships, both in terms of labor and impacts to operational fleet readiness.
Brass modeling also taps more accessible skillsets, rare as they are. “Brass model antenna measurements are fairly straightforward, whereas computational modeling in this challenging frequency band practically requires a Ph.D. in electromagnetics to perform simulations and interpret results. So we’re still at least ‘a few years’ out from fully transitioning from brass to computational modeling for high frequency.”
For now it’s Wong and the Gang, passing the torch one by one, soon from Wong to the model maker he’ll train as his replacement before he retires in two years. Wong has trade expertise to pass on, which he describes as old school, requiring a more nuanced touch than can be input via computer numeric control. By comparison, larger, automation-friendly machines at the Center’s machine shop are fit for mass production; here, one needs to be comfortable both using manual machines, such as a manual machine lathe, and tools — sanding, carving, and soldering one-off models that will be used for a lifetime.
“One of the fun things about that is seeing your product through, start to finish, step by step,” Blas said. “In the machine shop, you develop the skills to know which steps to take. Here, those skills are the same, it’s just that some of those steps are on smaller machines, and some are by hand.”
The group seems to share this ethos: one of precision, dedication, high attention to detail. “And camaraderie,” Blas adds. They say there simply wasn’t enough room in the shop to not end up friends.
Before I leave, O’Neill tells me to visit the Miniature Engineering Craftsmanship Museum in Carlsbad, so I do, marveling with my own division head at the tiny artistry and raving about the satisfaction that comes from using your hands to turn basic materials into something new. Looking at pictures and stories of people who spent decades building intricate dollhouses, functioning miniature engines — and thinking about the vibrant personalities back at the shop — it strikes me there’s an intangible, personal quality to models, marked by the modelers who make them.
We get to the model ship section and learn about William Tompkins, who, starting as a teenager, built more than 307 ship models at 1:600 scale. He was so good at it that naval intelligence personnel, shocked at seeing accurate representations of then-secret radar antennas hanging out on a model in a Los Angeles department store window, interrogated him as a suspected spy. He wasn’t a spy — just smart — so they asked him to join the Navy, just 17 years old.
He went on to build exceptional careers both in the Navy and in support of government projects after, a major contributor to plans for Apollo space missions. He looks a little like our technical director, whose dad interned in the model shop in the 1960s; I’d swear there was a relation if they didn’t have completely different last names.
 |
| 240222-N-ZB499-1031 SAN DIEGO (Feb. 22, 2024) Retired model ships rest in the “bone yard” outside the ship model shop at Naval Information Warfare Center (NIWC) Pacific in San Diego, Feb. 22, 2024. Testing antenna configurations on model ships before installing them on real ships 48 times the models’ size saves the Navy time and money by validating high-frequency radio communications coverage before any metal is cut in the shipyard. (U.S. Navy photo by Aaron Lebsack) |
Somewhere in this history — no one can say when — brass models began to fill first “the barn,” a shed next door for storing models still used for testing, then overflowed into the “bone yard” — a ship cemetery for retired models so eerily captivating that passersby, complete strangers, have pulled over to the side of the road to ask how to acquire one of those old model ships.
 |
| Model boneyard and Barn as seen from public road |
Before the barn and the bone yard, before Wong and Peralta and O’Neill, Blas’ time in the shop overlapped with Joe Havlick, the very first, who started in 1951 and retired in 1979. Havlick would come along for the model range in its second form, the wooden arch in 1948. It’d only take a handful of years for ship modeling to prove its cost effectiveness; when USS Mt. McKinley (AGC 7/LCC 7) was recommissioned in 1951, engineers at the Antenna Model Range proved they could reduce the number of antennas needed on Mt. McKinley by two thirds.
Between Wong and Havlick there’s a small club of 30 people who spent anywhere from a few months to a few decades here. Before all of them, all the way back at the start, there were just three 100-foot-tall telephone poles that simulated incoming radio waves at various frequencies, and engineers on the ground below doing pretty much the same thing they’re doing now. There were modelers and machinists, some middle-aged and some yet to be born, some for summer internships and some for lifelong careers, all set to intersect and overlap here at the bottom of the hill. Some of their friendships would span nearly 40 years.
If I could, if it were open to the public, I’d prescribe an afternoon in the model shop as a retreat from constant change — energizing but not often enough leaving time to look back and appreciate the ingenuity that came before. Here innovation has been suspended in time since the late 1940s, when they first found a solution hardy enough to survive more than 70 years of subsequent breakthroughs. It leaves one wondering whether we should measure our innovations more by their staying power — how much we get it right the first time — than by their novelty.
For now, just know there’s a place under that big white arch, a time capsule for a niche sort of person doing a niche sort of work more enduring than rumors about computers making another trade obsolete, where craftspeople do things the old way, simply because it works.
Visit Us - The Miniature Engineering Craftsmanship Museum
Hundreds of woodworking and metalworking projects exhibiting outstanding craftsmanship at the small end of the size scale.
The history of US Navy electronic technology at Pt. Loma
The history of electronic technology began on Pt. Loma a long time before the establishment of the laboratory here in 1940. On May 12, 1906, a chief petty officer and two sailors drove a horse-drawn wagon to the downtown pier and loaded up a massive 5-kw. transmitter/receiver, the state-of-the-art in communications. This was the new age of "wireless radiotelegraphy," which the Navy would eventually shorten simply to "radio." Many hours later, in the little station house they’d set up on top of the hill, the equipment had been installed. The chief sat down and tapped out a hopeful message to the Mare Island Naval Radio Station. He was hopeful, because the distance record for Navy wireless communication at the time was about 125 miles, and Mare Island was 500 miles away. He was stunned by an immediate reply, and in celebration commissioned the facility as Navy Radio Station Pt. Loma.
On June 1, 1940, Secretary of the Navy Frank Knox established the Navy's first laboratory on the West Coast, the U.S. Navy Radio and Sound Laboratory. Its mission was to perform research and development in communications and radio propagation. In 1943, a second West Coast laboratory was established in the high desert at Inyokern, Calif., the Naval Ordnance Test Station (NOTS), charged with improving naval weapons systems, particularly those dropped from aircraft. NOTS became the Naval Undersea Warfare Center, the Naval Undersea Research and Development Center, and the Naval Undersea Center (NUC).
The naming history and name changes across seven decades is convoluted, but this is a rough outline, subordinate commands are not complete for this list.
- (1940) U.S. Navy Radio and Sound Lab (NRSL) Who also worked together with UCDWR (University of California Division of War Research)
- (1945) U.S. Navy Electronics Laboratory (NEL) UCDWR and NRSL combined to create NEL
- (1967) Naval Command Control and Communications Laboratory Center (NCCCLS)
- (1977) Naval Ocean Systems Center (NOSC) - On March 1, 1977, NELC and NUC were consolidated to form the Naval Ocean Systems Center (NOSC)
- (1992) Naval Command, Control and Ocean Surveillance Center (NCCOSC) RDT&E Division (1992) combined to become NRaD
- (1997) Space and Naval Warfare Systems Center San Diego (SSC SD) (1997)
- (2008) Space and Naval Warfare Systems Center Pacific (SPAWAR Systems Center Pacific or SSC Pacific)
- (2019) Naval Information Warfare Center(NIWC)
 |
| Iowa class model at the antenna range, Pt Loma, Navy Electronics Laboratory. The model is made of wood and plated in brass. The model is 18'6" long, 27.5" wide and weighs 550 pounds. |
Back when it was NELC, San Diego Antenna Range -1949 Press Release -
In planning communications systems for ships at sea, Navy scientists seek to design shipboard antennas capable of sending out substantially the same amount of energy on all directions.
This problem is attacked at the US Navy Electronics Laboratory, San Diego, California, by the use of miniature ships whose topside structures are precisely scaled counterparts of full-sized naval vessels. these models make it possible to conduct investigations of shipboard antenna directivity under controlled conditions on land. Scale factors of 1/12, 1/24, and 1/48 are used in the studies and are applied both to the construction of the miniature ships and to the radio wavelengths most commonly encountered in shipboard communications.
In practice, the scale model is mounted on a turntable and rotated over a mesh of hardware cloth while it antennas are supplied with energy at the correct radio frequency. The hardware cloth simulates the conductivity of the ocean at regular communication frequencies. The radiated energy is received and its intensity measures at special stations on the rim of the "ocean". These measurements give radiation characteristics of the small antenna, and by extension, the performance of a full size antenna aboard a full size ship at communication frequencies.
The model shown is one of the "Long Hull" destroyer class, and is constructed of brass. The use of such models for antenna directivity studies avoids the heavy expenditures of money which would be necessary to obtain the same data if full-scale, fully manned ships were used at sea for this purpose.
A strangely silent fleet of brass warships can be seen operating on a lead-coated "ocean" high and dry atop the main NEL premises on Point Loma. The ships in this fleet never fire their guns, but their antennas are always busy. Built to 1/48 scale, they are part of the Laboratory's unique ship model antenna range.
Each ship is electronically complete down to the waterline. Each has operational antennas for transmitting and receiving radio signals at varying frequencies. Because metallic ship environments distort and alter the radiations from antennas, and obstructions topside provide added interference, antenna efficiency usually depends upon the placement, design, and number of the antennas.
The Laboratory tests the efficiency of a particular antenna design by sending and receiving signals in all frequencies while the ship model turns through the 360° of azimuth on a 22-foot turntable in the center of a 160-foot lead and wire-coated field. The coating provides environmental conditions roughly approximating those of the ocean.
An actual ship could make only a limited number of turns in a day, with consequent loss of operational time, manpower tieup, and interruption of other training. Moreover, changeable weather conditions would prohibit testing under controlled physical conditions, as is possible on a controlled range.
A further great advantage of the range is the design and test of communication systems as an aid to ship preliminary design. Technically, the artificial ocean is a conducting ground plane, and the experiments measure on the ship models vertically polarized components of horizontal-plane patterns in the 96 to 1440 megacycle range, simulating the 2- to 30-megacycle band.
A two-axis free space mount, available for measurement of zenith coverage patterns in the 1000 to 3000-megacycle range, can accommodate scale models (usually 1/4 scale) of ship masts and superstructures. Use of a wire mesh ground plane of about 40,000 square feet with five 90-foot wood poles permits realistic full-scale tests of simulated ship antenna systems, and an additional 120-by-150 wire mesh ground plane has a rotating antenna mount for development and test of specific antennas for ship and shore applications.
Ship communication mock-up facilities in the antenna range building make possible the study and development of complete ship radio communication systems under conditions simulating those aboard ship. Improvements now under way at the ship model range will permit absolute measurement of antenna patterns and extension of measurement to evaluation angles above the horizon.
Nearby microwave facilities include a range for rapid and accurate determination and recording of the free space radiation patterns, impedance, and gain characteristics of microwave antennas in the frequency range from 1000 to 10,000 megacycles.
NEL engineers must study as many as 3,000 to 5,000 radiation patterns for each new ship design. To lighten their workload the antenna range specialists recently devised a Pattern Analyzer Computer (analog to digital) equipment which is used to determine values required from the antenna patterns by an IBM computing machine.
Edit: Iowa class model at the antenna range, Pt Loma, Navy Electronics Laboratory. The model is made of wood and plated in brass. The model is 18'6" long, 27.5" wide and weighs 550 pounds.
Popular Mechanics 1959 story on NEL. Electronic Architects Shape Our Navy,
by Thomas E Stimson, Jr.
Story starts on page 81. More photos of the model makers and additional models used.
Edit: Popular Mechanics 1959 story on NEL. Story starts on page 81. More photos of the model makers and additional models used.
https://books.google.com/books?id=gtsDAAAAMBAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
The brass model was made for testing the radiation patterns of radio antennas. They were made of wood, plated with brass, typically 1/48 scale, although some were 1/12 or 1/24. These scales used in the studies are applied both to the construction of the miniature ships and to the radio wavelengths most commonly encountered in shipboard communications.
Shipboard communication problems initially believed caused by the weather and jamming were found in tests by NRSL in 1943 to actually stem from a closer, more controllable source--the ship itself. At HF frequencies, the engineers found, the entire platform was the receiver, and the increasingly large array of radiators on the topsides of ships, plus weapons launchers, smoke stacks, masts, and the like, were often responsible for communications problems.
In practice, the scale model is mounted on a turntable and rotated over a mesh of hardware cloth while its antennas are supplied with energy at the correct radio frequency. The hardware cloth simulates the conductivity of the ocean at regular communication frequencies. The radiated energy is received and its intensity measured at special stations on the rim of the "ocean". These measurements give radiation characteristics of the small antenna, and by extension, the performance of a full size antenna aboard a full size ship at communication frequencies.
The use of such models for antenna directivity studies avoids the heavy expenditures of money which would be necessary to obtain the same data if full-scale, fully manned ships were used at sea for this purpose.
S. R. Best, "On the use of scale brass models in HF shipboard communication antenna design,"
Introduction
One of the most interesting and educational aspects of my career as an antenna engineer was working on the design and development of HF, VHF, and UHF communication antenna systems used by the US and other navies. One aspect of this work was the design of HF communication antennas through the use of 1/48th-scale ship models, which were fabricated from brass. I had the opportunity to work on several of these projects when I was employed with Chu Associates, Inc., from 1987 through 1993.
In the design of shipboard communication antenna systems, the antenna design engineer and the ship structural design engineer must coordinate their efforts throughout the ship design cycle to ensure meeting minimal requirements for antenna performance, all while meeting the ship's overall design requirements. In addition to achieving the fundamental antenna-performance requirements, the communication system design effort has to consider the design requirements for EMI/EMC; radiation hazard (RADHAZ), and radar cross section (RCS). These aspects of system design occur simultaneously with the antenna design; however, they are beyond the use of scale models.
Optimum communication system performance is obtained by properly integrating the antennas into the ship's topside structure. From the perspective of the antenna's design, optimum performance is achieved when the low-elevation-angle azimuth radiation patterns are as circular as possible, with few or no pattern nulls. Additionally, the antenna design engineer seeks to maximize the antenna gain at these low elevation angles, and to prevent radiation from being directed upwards. Finally, the antenna design must provide a reasonable impedance match, such that the SWR specification is met over the full range of operating frequencies.
Achievable performance levels for a communications platform are greatly influenced by the layout of the equipment and the antennas relative to the ship's structure. The ship's structure – which includes numerous deckhouses, masts, exhaust stacks, armament, rails, and other metallic objects – interferes with the operation of the system antennas. RF currents induced on these metal objects are subsequently re-radiated; causing radiation-pattern nulling, conversion of vertical polarization to slant and horizontal polarization, and the re-direction of energy away from the intended low elevation angles.
Many times, the basic limitations imposed on the performance of the HF antennas by the ship's structure cannot be overcome by simple rearrangement of the antennas and equipment. These fundamental limitations can be overcome, however, by coordinating the design of the antennas with that of the ship's structure. HF antennas properly integrated into the ship's structure can be configured to provide optimum system performance. To achieve acceptable results economically, the coordinated design effort must be accomplished early in the ship's design cycle. Scale-ship-model antenna range studies are ideal for this purpose.
Using naval architectural drawings for the ship, a master model maker fabricates an almost exact scale model of the ship's hull and topside structure. The scale model begins at the ship's waterline, and includes all of the major structural details at every level. The scale model includes ladders, armament, masts, stacks, antennas, and all other external physical structures, which is necessary for obtaining reliable scale-model test results. Fabrication of these elaborate scale models typically takes as long as six to eight weeks.
Once the fabrication of the scale model of the ship is complete, it is moved to the ship-model range, where impedance, cou- pling (interference), and radiation-pattern measurements are made at scale frequencies. The single objective of the scale-model study is the optimization of the HF communication systems1 performance. In many instances, the system antennas have to be relocated several times in order to achieve this optimum performance. Many times, optimum communication performance also requires changes in the design and configuration of the ship's topside structure. Once an acceptable antenna design and structural layout are obtained, this information is translated onto the ship's architectural drawings, so that the antenna system layout and any required structural changes are properly incorporated into the construction of the ship.
In most cases, the HF antenna design task does not end with the scale-model study. Although the results of the scale-model study are very accurate, many changes in the ship's structural design may occur between the model study and the final construction of the ship. In these instances, it is necessary to perform full-scale impedance measurements on board the ship, so that the final antenna installation provides optimum SWR performance.
This paper is intended to provide a brief historical overview of the US Navy's shipboard scale-model program, as well as a discussion of some of the technical and design issues associated with HF communication antenna system design using the scale brass models.
Historical Perspective
In deploying an HF communication system aboard a ship, integration of the system antennas within the ship's topside structure is critical in determining system performance. In many instances, there may be regions in the antenna's radiation patterns where nulls exist, limiting the effectiveness of the communications system. In order to be aware of these potential regions of limited performance, knowledge of the antenna's radiation pattern is required. Prior to the use of scale models and computer simulations, full-scale measurements of the antenna's radiation pattern were required, in order to evaluate communication system performance, This section provides a brief historical overview of the US Navy's efforts in developing a capability to evaluate and design HF communication antennas through the use of scale models.
2.1 The Naval Research Laboratory (NRL)
During World War II, technical responsibility for the development and implementation of the US Navy's HF communication systems rested with the Naval Research Laboratory (NRL). To evaluate and optimize shipboard antenna system performance, the NRL engineering staff had to be able to determine the radiation patterns of various antenna systems as installed on board ships. At the time, the NRL staff actually made full-scale radiation-pattern measurements of some 100 ships of various classes. These ship classes included battleships, aircraft carriers, and communication ships (AGC class) [1].
The full-scale radiation-pattern measurements were made offshore of NRL's Chesapeake Bay facility. The antenna-pattern measurements were made by having a small vessel circle the ship while the shipboard antenna transmitted a continuous signal. An alternate measurement method was having the ship circle a station- ary buoy, while the transmitted signal was measured onshore. One obvious limitation of these radiation-pattern measurement techniques was the fact that elevation-pattern data for the antenna was unavailable.
Although these full-scale measurements allowed the NRL engineers to determine the location and severity of radiation-pattern nulls, it was difficult to do much about them. Of paramount concern to the Navy at the time was the fact that the ships were needed for deployment in operational missions. Additionally, any re-location of the antenna systems, or any full-scale modification of the ship's structure, was costly and very time consuming. Any changes in the antenna system would require further full-scale measurements for improvement verification.
In an effort to improve the shipboard antenna design procedures, Navy engineering personnel devised a technique whereby scale models of the ship were fabricated and subjected to scale measurements, in order to evaluate and optimize antenna system performance. The use of brass scale models for measurement and evaluation purposes allowed for a dramatic decrease in the time required to complete engineering studies. Changes in the model's topside structure could be made quickly and easily, expediting the entire design process.
Reviewing some of the limited Naval historical documentation to which I had access, it is not clear where the first use of scale models occurred in the design and evaluation of shipboard HF communication antennas. NRL documentation credits the NRL engineering staff with devising this technique and subsequently using it in 1948 [1]. The ship-model range was constructed on the roof of a building, while the test equipment was located in the building beneath the range. The range was initially comprised of an 18 ft by 18 ft ground screen, upon which the scale models were mounted. At the time, this range did not include any capability for elevation-pattern measurements.
Scale factors up to 1/120th (0.1 in equals 1 ft) were initially used in the scale-model studies. To increase model and measurement accuracy, the maximum scale factors were eventually reduced to 1/48th scale (0.25 in equals 1 ft). One of the first scale-model measurement programs performed at NRL was for the Guppy-type submarine (SS 350). A 1/24th scale factor (0.5 in equals 1 ft) was used in these measurements to develop a sleeve antenna, incorporated into the submarine's conning-tower structure. One of the early 1/48th-scale-model studies was performed for the USS North Hampton.
During the mid- to late 1960s, the NRL model range underwent some significant improvements. The NRL facility in Brandywine, Maryland, included a 1000 ft diameter ground screen, and a 15 ft diameter turntable for rotating the scale-model ships. During the 1970s, the NRL ship model range was in limited operation as the US Navy's east-coast model-range facility. The NRL range became less active, as many of the scale-model engineering programs were conducted by commercial companies, or by the US Navy's west-coast model-range facility, located in San Diego. During the 1980s, the NRL model range became inactive.
2.2 The Naval Electronics Laboratory (NEL)
During the mid- to late 1940s, the US Navy also developed additional model-range capabilities on the west coast by con- structing a scale ship-model-range test facility at the Naval Electronics Laboratory (NEL), in San Diego. This scale model range is still operational, under the command of the Space and Naval Warfare Systems Center, San Diego (SSC SD). This model range has a turntable diameter of 22 ft, which is necessary in order to accommodate some the larger US Naval vessels. Additionally, the NEL model range has a wooden arch constructed over the turntable, to allow the shipboard antenna's elevation patterns to be measured.
In the previous section, it was mentioned that it is unclear as to when the first shipboard scale-model study occurred. NRL documentation credits the NRL facility with performing the first scale-model study in 1948. However, the NEL facility was performing scale-model range studies as early as 1946. An early NEL report [2] describes the results of a scale-model study performed using a 1/48th scale model for the CL-98 light cruiser.
2.3 Commercial Facilities
2.3.1 DECO/Westinghouse
One of the first private commercial scale-model antenna ranges was constructed and operated by Developmental Engineering Corporation (DECO), in Leesburg, Virginia [3]. DECO's first scale-ship-model range was operational in 1952. This scale-model antenna range consisted of a 3 ft diameter, rotating turntable, located in the center of a 40 ft by 50 ft ground screen. This range was used extensively for a number of US Navy ship programs, including destroyer and destroyer-escort ship classes. From 1956 through 1961, DECO constructed a number of additional scale-model pattern and impedance ranges. One of the pattern-measurement ranges included a 15 ft diameter turntabie, located in the center of a 60 ft by 100 ft ground screen. Some of the scale factors used by DECO in their various scale-model programs included 1/24th, 1/30th, 1/48th, and 1/72nd scale.
During the period from the early 1950s through the late 1970s, the DECO organization participated in a number of scale-model studies for the US Navy. In fact, at some points in time, DECO was performing more scale-model studies for the Navy than were the Navy-owned facilities. At some point in their history, DECO was acquired and subsequently operated by Westinghouse. The DECO/Westinghouse facilities are no longer operational.
2.3.2 Chu Associates
During the late 1950s and early 1960s, the NEL ship-model-range facility was headed by Mr. Valor C. (Val) Smith. Also employed at the NEL model range at that time was Mr. John O. Watson, who worked on numerous Navy shipboard programs as an antenna design engineer. In the early 1960s, Chu Associates, Inc., headquartered in Massachusetts, decided to open a branch office in the San Diego area (ElCajon), to support the US Navy's west coast operations. It was the intention of Chu Associates to design, develop, and manufacture communication antennas for the US Navy at their El Cajon facility. Additionally, Chu intended to construct and operate a scale ship-model test range at this facility.
In order to facilitate setting up the Chu West operation, including the construction and operation of the ship-model range, Chu hired both Val Smith and John Watson. By the mid-1960s, Chu Associates' west coast facility and ship-model range were fully operational. Chu Associates' ship-model range supported a number of US and foreign navy antenna design programs until the facility was closed, in 1992.
Some of the programs for which Chu Associates performed both shipboard antenna-model range studies and HF antenna design included the DD-963 Spruance-class destroyer, DD-993 Kidd-class destroyer, CG-47 Ticonderoga-class cruiser, DDG-51 Arleigh Burke-class destroyer, CG-26 Belknap-class cruiser, CVN-68 Nimitz-class carrier, LHA-1 Tarawa-class amphibious assault ship, Canadian patrol frigate, Indian Naval frigate, Iranian Naval frigate, Israeli SA'AR 5 corvette, Canadian Trump destroyer, and several others.
The Chu Associates Shipboard Antenna Model Range
Chu Associate's ship scale-model range was constructed at the Chu West facility in El Cajon, CA, during the early 1960s [4]. The scale-model range, pictured in Figure 1, consisted of a large, level, highly conducting ground screen, which simulated the ocean, and a central, 22 ft diameter turntable. The conducting ground plane was approximately 50 ft by 70 ft in size. The conducting ground plane was constructed of wire mesh, laid over and secured to a concrete slab. All joints in the ground plane were soldered, to ensure continuity across its surface.
The ship models, accurately scaled to 1/48th size, were mounted on the turntable and rotated, in order to measure the azimuth and elevation radiation patterns of the HF shipboard antennas. Several typical ship models are depicted in Figures 2, 3, and 4. Note that at 1/48th scale, the DD-993, DDG-47, and DD-963 models were physically 11.7 ft, 10.7 ft, and 11.7 ft long, respectively. The LHA-1 model was 17 ft long, and the CVN-68 model was 22.8 ft long.
Typical scale-model ships, at a 1/48th scale factor. Shown (I-r) are the DD-993 Kidd class, DDG-47 Aegis class, and DD-963 Spruance class destroyers.
Impedance measurements were conducted with the turntable stationary, from an access pit located beneath the turntable. All RF measurements were made in the 96 to 1440 MHz range, simulating the HF shipboard communication band of 2 to 30 MHz. All of the foreign ships modeled were fabricated at a metric, 1/50th scale factor (2 cm equals 1 m), as all of the construction dimensions were metric. In this case, the measurement scale frequency range was 100 to 1500 MHz.
When radiation-pattern measurements were taken, the antenna(s) on the model ship received signals from transmitting antennas located at the edge of the ground screen, or from antennas on a 40 ft radiusA frame. Fabricated from large, laminated epoxy fiberglass tubes, the A-frame arch provided rigid support and accurate radius for overhead pattern-coverage measurements, up to 90° elevation.
The receiving equipment was located under the turntable, in an underground pit. A polar-pattern recorder/plotter, connected to the receiving equipment, was synchronized with either the turntable's rotation, or with the vertical travel of the A-frame arch, to autornatically record azimuth- or elevation-plane antenna patterns. The radiation-pattern measurements were calibrated using the absolute response of a vertically polarized quarter-wavelength monopole antenna, measured at each test frequency. The response of the quarter-wavelength monopole was inscribed on each radiation pattern, or it was used as the maximum level on the recorder paper. In later years, the polar-pattern recorder/plotter could be replaced with an automated data-acquisition system, to record pattern data directly to a computer for subsequent analysis and plotting. Figures 5 and 6 present a functional block diagram of the test-equipment setup.
A functional block diagram of the ship-model-range test equipment setup, using manual data acquisition and pattern plotting.
A functional block diagram of the ship-model-range test equipment setup, using automated data acquisition with computer control.
Us Naval Hf Communication Systems
Through the late 1980s and early 1990s, the standard US Naval HF communication system operated in three subbands, within the standard HF frequency range of 2 to 30 MHz. These subbands were 2 to 6 MHz, 4 to 12 MHz, and 10 to 30 MHz. Although the Navy currently operates within these subband divisions, the newer communications standard High-Frequency Radio Group (HFRG) operates in two subbands: 2 to 8 MHz and 8 to 30 MHz (approximate frequency subdivisions). In both cases, some redundancy is designed into the communications system through the frequency overlap of adjacent subbands.
The HF frequency subband divisions were dictated by antenna and RF filter (multi-coupler) design limitations. Currently, the Navy uses broadband HF antenna systems that are designed to interface with either a “narrowband” or a “broadband” RF distribution system. The narrowband RF distribution system uses a series of tunable RF filters to provide the transmitters or receivers with access to a compatible broadband transmitting or receiving antenna. The broadband RF transmitter distribution systems provide a means to route the transmitter baseband signals to linear power-amplifier banks that interface directly with the broadband antennas. The broadband RF receiver distribution systems receive signals by means of either a physically small active antenna, or a small linear antenna the outputs of which are directed to active broadband multi-couplers. The effective heights of the small receiving antennas are set to achieve a specified output for a nominal, incident field strength.
The HF transmitter system typically utilizes an AN/URT-23 HF transmitter, capable of voice or data operation over the entire 2 to 30 MHz frequency band. These transmitters are connected to one of three multi-couplers: the AN/SRA-56 (2 to 6 MHz), the AN/SRA-S7 (4 to 12 MHz), or the AN/SRA-58 (10 to 30 MHz). The use of the multi-couplers allows multiple transmitters, with appropriate frequency separation, to operate into one antenna system. Alternately, the URT-23 transmitter can be operated directly into a single antenna, with an AN/URA-38 tuner/coupler located at the antenna.
This typical communication-system arrangement requires at least four types of HF transmitter antenna systems operating onboard the ship. With a URT-23 and URA-38 combination, the antenna is typically a single, 35 ft whip radiator. In this configuration, an impedance-matching network is not required, because the antenna is operated with an active tuner. With the URT-23 and SRA-56/57/58 combinations, the multi-coupler is directly connected to the antenna without employing a tuner. Therefore, a broadband impedance-matching network is required at each antenna installation.
The 2 to 6 MHz antenna is typically a twin-fan antenna, operated with a broadband impedance-matching network providing a maximum SWR of 3.0:1 at its input connector. The 4 to 12 MHz antenna system typically consists of a twin 35 ft whip antenna and broadband impedance-matching network combination. The antenna system is designed to provide a maximum SWR of 3.0:1 over the operating band. The 10 to 30 MHz antenna system typically consists of a twin 12 ft, 16 ft, or 18 ft whip antenna and broadband impedance-matching network combination. Again, the antenna system is designed to provide a maximum SWR of 3.0:1 over the operating band.
The URT-23 and SRA-56/57/58 combination can safely operate into a 3.0:1 SWR impedance load. These transmitter systems are specifically designed to dissipate reflected RF power to eliminate multiple reflections between the transmitter and the antenna. As the load SWR increases above 3.0:1, the transmitter gradually decreases its output power to minimize the level of reflected power reaching the transmitter system. At some point – typically, above a 4.0:1 SWR – the transmitter will shut down completely. Although the HF transmitter design specifications require a maximum antenna SWR of 3.0:1, it is not uncommon for the shipboard installation to have maximum SWR levels of 3.5:1, or slightly higher. The coaxial cables used in these shipboard HF antenna systems are typically 1.625 in or 3.125 in diameter low-loss cables. With air dielectric, these cables have matched attenuation levels of 0.112 dB/100 ft and 0.075 dB/100 ft at 30 MHz, respectively. Therefore, the multi-couplers are essentially loaded at the antenna's matching-network input SWR.
The
passive receiver antennas used on board ship are typically 18 ft or 35
ft whip radiators, which are connected directly to the coaxial cable
through a junction box. This junction box simply provides a mechanical
and electrical interface between the coaxial-cable connector and the
wire-rope feed line attached to the antenna. The junction box also
contains a
The Hf Antennas
As mentioned in the previous section, the HF antenna suite typically consists of a 2 to 6 MHz twin fan, a 4 to 12 MHz twin whip, and a 10 to 30 MHz twin whip. This section provides additional design and construction details for each of these antenna systems.
5.1 The Twin-Fan Antenna
The antenna design problem at 2 MHz is complicated by the fact that the wavelength at this frequency is approximately 492 ft.
A quarter-wavelength monopole, being 122 ft tall, is an unacceptable design for shipboard applications. Even at a frequency of 6 MHz, where the wavelength is approximately 164 ft, a quarter-wavelength monopole, being 41 ft tall, represents a significant mechanical design problem. This is primarily a result of the fact that shipboard-antenna systems must meet rigid shock and vibration specifications. The most commonly deployed transmitter antenna for the 2 to 6 MHz frequency spectrum is the twin-fan antenna [5], [6], as illustrated in Figure 7 [7]. This antenna is also used in the receiving mode over a much broader frequency spectrum, up to frequencies of 15 to 20 MHz. The twin-fan antenna is comprised of two sets of wire-rope fans, which mount from an upper-mast yardarm and extend down to deck level. This wire arrangement allows a longer wire length to occupy a smaller vertical profile. Each fan section is typically comprised of three or four insulated phosphor-bronze wires, which are isolated from the ship's metallic structure through Delrin® strain insulators. Using three or four wires in this fan arrangement provides for bandwidth improvement, compared to using just a single wire. Each fan wire may typically be up to 70 ft or 80 ft in length, or greater. A scale-model version of a twin-fan antenna is depicted in Figure 8.
The feed point for the twin fan is located on the mast, typically at the yardarm level, such that the fan is fed at the top of its structure. The fixed impedance-matching network for the fan is housed within a rugged aluminum container. The internal matching components typically include adjustable high-voltage vacuum capacitors, and copper inductors that are made from 0.125 in or 0.25 in refrigerator tubing. Connections between the matching-network components are typically made using flat copper strips, designed to minimize series inductance. The impedance-matching-network components are typically connected to each fan section through separate Delrin® insulators. A typical matching-network container is shown in Figure 9.
A significant point to note is that, in and of itself, the twin-fan radiator is not the “antenna.” The twin-fan structure becomes an effective radiator by exciting currents on the ship's structure, which are then re-radiated. In essence, the entire ship – or a major portion of the ship – functions as the total antenna system. The portion of the ship that the twin fan is specifically designed to excite is the mainmast or foremast, as the ship's design will allow. In many cases, in order to implement an effective twin-fan antenna system, basic changes in the mast structure (usually, its height) are required.
5.2 The Twin-Whip Antenna
At the higher operating frequencies of 4 to 12 MHz and 10 to 30 MHz, the wavelength is physically more reasonable, so that common antenna designs, such as vertical monopoles, become usable in shipboard applications. With the exception of height, the 4 to 12 MHz and 10 to 30 MHz twin-whip (monopole) antennas are of similar design and construction [5], [8]. These twin-whip antennas are typically used in both receiving and transmitting modes. Depicted in Figure 10, the twin-whip antennas consist of two separate aluminum whip radiators, which are isolated from the ship's structure at their base through high-strength fiberglass insulators. Twin whips are used in these designs to increase the effective diameter of the radiator, thus improving bandwidth performance over that of a single-whip radiator. The radiating section of each whip is manufactured from sectional spun-aluminum tubing, virtually identical to that used in the manufacture of aluminum light poles. The shipboard spun-aluminum sections are of stronger construction, in order to survive the shipboard shock and vibration requirements. An impedance-matching network is located centrally between the two whips. The RF connection is made through phos-phor-bronze wires, which connect the base of the radiating section to the two Delrin® insulators on the matching network. Scale-model versions of these antennas are illustrated in Figures 11 and 12.
The Design and Measurement Process
The primary objective of the scale-model antenna study is to design an antenna system that provides optimum performance for the entire suite of HF communication antennas used aboard ship. The performance criteria evaluated include the antenna's impedance and associated SWR properties, the radiation-pattern properties, and the antenna-to-antenna coupling (interference). For each antenna system, a set of performance-specification goals is established for the operating frequency band. The performance-specification goal for transmitting-antenna SWR, with respect to a 50 ohm impedance, is typically a maximum of 3.0:1 over the entire operating-frequency band. The performance-specification goals for the antenna's radiation patterns are more involved, and typically include a specification for pattern circularity, average horizon gain, the location of the major pattern lobe, and polarization purity. In many cases, there may not be a coupling specification, and the coupling measurements are made for reference purposes, only. A typical set of HF antenna performance-specification goals is presented in Table 1.
In the initial phase of the design study, the ship's operational requirements and its electronic equipment suite are reviewed, to determine the types and quantities of antennas that best meet the needs of the ship. As a result of this initial review, an HF antenna suite is proposed to meet the ship's operational requirements. This HF antenna suite description also includes proposed locations for each of the HF antennas. The HF antenna suite definition provides a detailed configuration list of the number and types of antennas necessary to implement the required number of communications circuits in each frequency spectrum. The number of HF communications circuits is a direct function of the number of transmitters, transceivers, receivers, and the multi-coupler equipment to be installed aboard ship.
In the second phase of the study, the various candidate antenna types and mounting locations are examined, using the model to determine their baseline performance in the shipboard environment. Changes to the antennas' locations and to the ship's topside structure are made as necessary, in order to optimize the antenna system performance. In the final phase of the program, the recommended antenna systems are installed on the ship model, and detailed impedance, radiation-pattern, and coupling measurements are made, in order to evaluate and report on the final antenna performance.
In many instances, the second and final phases of the scale-model study are simply a combined design and analysis effort. Typically, the first baseline performance measurement made is the antenna's feed-point impedance. Limited preliminary radiation patterns are also measured, in order to establish the baseline pattern performance. Using the measured antenna feed-point impedance, the initial design effort begins with the design of a broadband impedance-matching network for each of the antennas. Once an acceptable matching-network design is determined, actual scale-model components – consisting of discrete inductors and capacitors – are installed onboard the scale ship at the antenna feed point(s). Final performance measurements are then made with the scale-model matching networks installed.
One significant design issue
considered is the fact that the scale matching-network components will
have performance properties that are different from their full-scale
counterparts, in terms of their
Typical
input impedance data for a broadband twin-fan transmitting antenna
measured on a scale model, with a scale-model matching network
installed.
A typical 1/48th scale model twin-whip antenna, with a scale matching network installed.
Radiation-pattern measurements are made over the full 2 to 30 MHz frequency band, as a function of the specific operating frequency subband of the antenna being tested. In the 2 to 6 MHz subband, radiation patterns are recorded at every 0.2 MHz for a total of 21 discrete frequencies. In the 4 to 12 MHz subband, radiation patterns are recorded at every 0.2 MHz up to 6 MHz; at every 0.5 MHz from 6 to 10 MHz; and at every 1 MHz from 10 to 12 MHz, for a total of 21 discrete frequencies. In the 10 to 30 MHz subband, radiation patterns are recorded at every 1 MHz up to 20 MHz, and at every 2 MHz up 30 MHz, for a total of 16 discrete frequencies.
At each frequency, the radiation-pattern measurements include azimuth radiation patterns at different elevations between 0° and 60°. A typical set of azimuth patterns includes elevation angles of 3°, 12°, 20°, 30°, and 60°. A set of elevation-pattern measurements is typically made at relative headings of 0°, 90°, 180°, and 270°. Both horizontal and vertical polarizations are measured in each case. As a result of the number of measurements at each frequency, a total of 378 patterns are typically measured for a 2 to 6 MHz twin fan and a 10 to 30 MHz twin whip. A total of 288 patterns are typically measured for a 10 to 30 MHz twin whip. A typical set of radiation-pattern measurements, performed on a twin-fan antenna at a scale frequency of 192 MHz (4 MHz full-scale), is presented in Figure 15.
A typical measured azimuthal pattern for a twin-fan antenna at 4 MHz, at 3° elevation. The solid line is
A typical measured azimuthal pattern for a twin-fan antenna at 4 MHz, at 12° elevation. The solid line is
A typical measured azimuthal pattern for a twin-fan antenna at 4 MHz, at 20° elevation. The solid line is
A typical measured azimuthal pattern for a twin-fan antenna at 4 MHz, at 30° elevation. The solid line is
A typical measured azimuthal pattern for a twin-fan antenna at 4 MHz, at 60° elevation. The solid line is
A typical measured elevation pattern for a twin-fan antenna at 4 MHz, in the zenith plane, at 0° azimuth, for
A typical measured elevation pattern for a twin-fan antenna at 4 MHz, in the zenith plane, at 90° azimuth, for
A typical measured elevation pattern for a twin-fan antenna at 4 MHz, in the zenith plane, at 180° azimuth, for
A typical measured elevation pattern for a twin-fan antenna at 4 MHz, in the zenith plane, at 270° azimuth, for
In summary, the overall design and analysis effort typically includes the following:
Impedance-matching network design and determination of matching-network component values for each antenna.
Measurement of impedance and SWR at the input to theantennas' matching networks.
Measurement of radiation-pattern circularity of the antennas.
Determination of average horizon gain of the antennas.
Determination of the low-angle radiation-pattern coverage of the antennas.
Determination of the predominant polarization of the antennas.
Determination of the RF coupling between antennas.
Other Hf Antenna Systems
In addition to the HF twin-fan and twin-whip antenna systems, the ship scale models were used to aid in the design of a variety of other HF communication-system antennas, used in both transmitting and receiving applications. These antennas included log-periodic dipole arrays, discage antennas, monocone antennas, and a variety of wire-rope and whip receiving antennas [5]. The directional log-periodic antennas were used to provide higher-gain directional coverage over a broad range of HF frequencies, while the discage and monocone antennas were used in applications requiring wider bandwidth or higher power capability than provided by twin-whip antenna configurations. A somewhat typical scale-model antenna configuration, as installed aboard a scale ship model, is illustrated in Figures 16 and 17. Evident in these photographs are the numerous log-periodic antennas, and the deck mounted discage antenna. A clearer view of the HF log-periodic antenna is shown in Figure 18.
The LHA-1 Tarawa-class 1/48th scale model antenna installation, starboard view. An HF log-periodic antenna is on top of the mast on the left; an HF discage antenna surrounds the mast in the center.
The forward view of the LH1A-1 Tarawa-class 1/48th scale model antenna installation.
The full-scale HF log-periodic antenna was manufactured by Chu Associates as model CA-3038A. It has a Navy designation of AS-2874/SRC. The full-scale antenna operated continuously from 7.5 to 30 MHz, with a maximum SWR of 2.5:1 and a power-han-dling capability of 10 KW average. The antenna could be rotated; it was 47.2 ft long and weighed 1,533 lb. The full-scale discage antenna was also manufactured by Chu Associates as model CA-3195, with a Navy designation of AS-2802/SRC. The full-scale antenna operated in two frequency bands, 4 to 12 MHz and 10 to 30 MHz, with a maximum SWR of 3.0:1 in each band. The discage antenna was 32.75 ft tall and weighed 733 lb without the support mast. It had a power-handling capability of 12 KW average.
Summary
The performance of HF shipboard antenna systems is highly dependent on the arrangement and configuration of the ship's superstructure. Since full-scale measurements are cost prohibitive, time consuming, and cannot be made until after the ship is constructed, an alternate methodology is necessary to facilitate the design and evaluation of HF shipboard antenna systems. The use of scale ship models provided the US Navy with a cost-effective method to facilitate shipboard antenna design and evaluation. The use of scale models provides the antenna design engineer with a mechanism to consider the integration of the antenna system into the ship's superstructure as part of the design process. Through changes in the antenna's location and shipboard superstructure, optimum antenna performance can usually be achieved. Once the antenna system design is finalized, the antenna configuration and location can be translated into the full-scale ship design.
As part of the engineering design effort, impedance-matching network configurations are designed and then translated into the manufacturing of full-scale matching networks. Numerous radiation-pattern measurements are taken, including azimuth and elevation patterns for both vertical and horizontal polarizations. The primary performance objective is to keep radiation at low elevation angles, and to maintain the best possible azimuth-pattern circularity. This design process is accurate, cost effective, and easily accommodates on-going or future changes in the ship's super-structure. In many cases, the use of brass scale models is as effective – and, in some cases, more effective – than the use of computer simulations.
ACKNOWLEDGMENT
I would like to thank Mr. Val Smith and Mr. John Watson for sharing with me their valuable experience in the design and development of HF, VHF, and UHF shipboard communications antennas. Prior to his retirement, Mr. Smith was Vice President and General Manager at the Chu West facility in El Cajon, California. Mr. John Watson was Senior Electrical Engineer at the Chu West facility, and was responsible for Chu Associates' shipboard model design studies and subsequent antenna designs. It was a pleasure and valuable learning experience working with these two individuals.
I would also like to thank Mr. Richard Pride for all of the valuable discussions on the US Navy's shipboard communications systems and various programs. Mr. Pride was formerly at the Space and Naval Warfare Systems Command in Washington, DC, as Head of the Communications Antennas Section.
No comments:
Post a Comment