Decades ago, western defense industry contractors and armed forces downplayed the usefulness of meter-wavelength radars of Soviet/Russian origin, but they are still going strong in several countries around the globe. Although a member of NATO for nearly seven years now, Hungary not only still operates such radars, but also modernizes them with the clear aim of developing an indigenous design and using VHF frequencies for prospective bi- and multi-static systems (see Figure 1).
Radar units of the former Warsaw Pact (WP) armed forces usually employed an array of radars operating in bands covering meter, decimeter and centimeter wavelengths. In addition to technological and manufacturing reasons (lower frequency radars were generally cheaper), the Soviet-model air defense systems retained this diversity to present a huge challenge for NATO electronic-warfare planners. The often-overlooked factor in maintaining this diversity, however, was the fact that different operating bands offered an opportunity to utilize the best properties associated with each of them. Being “high end” metric radars, the semi-fixed P-14 and the deployable Oborona (NATO: Tall King A and C), with their high gain parabolic antennas, acted as very long-range surveillance sensors for the contemporary integrated air defense system (IADS) at selected sites. They also served as target-acquisition radars for the S-200 (NATO: SA-5 Gammon) extra long-range surface-to-air missile (SAM) system. At the same time, much simpler and cheaper P-12 and P-18 radars (NATO: Spoon Rest), with their multiple Yagi arrays (see Figure 2), were employed by all radar posts as their metric component, and SAM batteries (such as SA-3 and SA-2) used them as an embedded target-acquisition sensor (see Figure 3).
While not a well-known fact, these two classes of metric radars were also combined in a special project throughout the WP, unofficially known as the “P-13.” Each country’s radar engineers matched some of their P-12 equipment with the huge array of the P-14 to increase detection performance. Actual technical realization varied, but the Hungarian way of coupling the backend with the antennae earned respect as the most efficient solution.
Under the Soviet system, the role of metric radars proved to be enduring, but their importance was elevated by the developments in Western threat technologies beginning in the 1970s. Faced with the emergence of small targets like cruise missiles or targets with low observable technologies — generally, targets with small radar cross-sections (RCS) — metric radars became clearly irreplaceable, as higher frequency radars could not handle such targets with sufficient efficiency. At the same time, it also became evident that these radars could not be targeted by anti-radar missiles (ARM), as those weapons do not have enough space to house a homing antenna big enough to fulfill their mission against radars operating at this wavelength. With the dissolution of the Warsaw Pact, this threat perception disappeared — at least in the Central and Eastern European countries that had just become independent from the Soviet Union. Along with joining Western institutions like NATO, large-scale downsizing of the armed forces was on the agenda. Radar communities focused on establishing new, much smaller structures offering a minimum of coverage to support peacetime air sovereignty. This general trend, however, was abated — at least for a short period — in Hungary, which had a serious security problem on its borders: the violent disintegration of Yugoslavia beginning in 1991. The experience of that conflict for the Hungarian Defense Forces (HDF) showed a continuing need for the detection of low level targets by easily deployable, simple, “wartime” gap-fillers.
Reflecting the philosophy of “frequency diversity,” temporary radar posts deployed along the southern border of the country consisted of centimetric (ST-68U Tin Shield), decimetric (P-15 Flat Face and Kasta-2) and metric (P-18) radars, as well as PRV-16 (Thin Skin) altitude finders. Being the cheapest elements, both the P-18 and the P-15 were available to the HDF in rather large numbers for such tasks. However, while the metric radar survived the downsizing, the post-Cold War service of decimeter-band equipment was cut short by unexpected external developments. In addition to being described as “simply archaic” by 1990s-era operators, the fate of the P-15 Dzhigit was finally sealed by the increasing commercial utilization of the UHF band (300 MHz to 1 GHz), mostly for communications purposes. The lobbying power of the HDF in frequency allocation was not even enough to keep its brand-new successor, the pulse-compression Kasta-2 system, in service. In contrast, the P-18 earned a new lease of life, though it had and still has to fight similar threats to its existence. From the viewpoint of the HDF, relatively low operating costs and growth potential made it a perfect piece of equipment in the cost-cutting post-Cold War environment. “Human factors” also played a part in the continuation of Hungarian metric-radar operations, as several officers remained in charge whose thinking was influenced by the philosophy of “frequency diversity.” While the wavelength question was being addressed, it was also decided that metric radars had to undergo modifications reflecting contemporary technology levels and the current Hungarian (that is NATO IADS) operational requirements — much like other legacy radars, such as the centimetric P-37 (Bar Lock). Before increasing actual radar performance, however, priority was given to ensure radar-data compatibility with new command-and-control nodes, like the US-financed Air Sovereignty Operations Center (ASOC), which require certain digital input formats. For this task, special interfaces were developed that basically transformed the analog output of these radars into digital data, as required. After initial interfacing was achieved, concepts were developed to improve the biggest deficiencies in the radars themselves, such as high manpower requirements, low mean times between failures (MTBF) and unsophisticated signal processing. Though initial research and prioritization of tasks were conducted by the Ministry of Defense (MoD) Technology Agency, the actual modernization program for the P-18 started in 2000 at Arzenal stock company, a specialized defense firm located in Nyirtelek, in eastern Hungary.
While the modernization effort has not altered the transmitter, an integrated solid-state unit has replaced the entire receiver and signal-processing system. Being software-controlled, this unit has taken over the role of several original hardware units, which could then be taken out of the cabin, making it more spacious and comfortable (see Figure 4). The use of new components and the decrease in the number of parts, in turn, improved the MTBF and shortened the time required to set up and test the equipment. Also worth noting is the VHF correction algorithm embedded in the tracker, which compensates for the signal-fragmentation phenomena characteristic of metric radars. In addition to the integrated PC-based control and display unit in the cabin, there is also a remote control and display unit that can be deployed away from the radar, connected via a single coaxial cable. The new receiver and signal-processing system also permits the supply of data in the required format to the ASOC and other currently operational command-and-control systems, as well as NATO’s future Air Command and Control System (ACCS). Arzenal handed over the first modernized P-18 to the Hungarian Air Force in 2002, and additional upgraded systems have since been delivered to the 54th Airspace Control Wing and the 12th SAM battalion. With the arrival, beginning in 2006, of the new NATO-financed Selex (Alenia Marconi) RAT-31D long-range surveillance radars, the main task of the modernized P-18s will be to fill the gaps left in their coverage according to actual needs or as dictated by the threat situation. With the SAM unit, they will act as embedded target-acquisition sensors, sending data to modernized K-1P mobile command posts, which in turn cue the Kub and Mistral missile systems. Again, frequency diversity has prevailed, as the modernized P-18s are paired with modernized centimetric ST-68U radars.
While modernization efforts seems to have paid off already, the Technology Agency and a small private electronics firm went further by developing an indigenous radar — the first for Hungary since 1945. Although Budapest-based Sagax Ltd. had been mostly engaged in the development and manufacturing of radio-interception and direction-finding equipment, the company realized how useful its experience with software-radio technology could be in radar development. Designated the SRV-P-18, the 200 W model and the 3 kW prototype of the new radar utilizes the existing antenna mechanics of the P-18 but otherwise is an entirely new design. Using a sub-pulse modulated transmitter and a matched-filter pulse-compression receiver, it promises to overcome several limitations inherent in conventional VHF radars, while code-modulated pulses and random frequency-hopping modes are improving the system’s resistance to electronic countermeasures (ECM). Engineers and university students involved in the program introduced their wholly commercial, off-the-shelf-based model to insiders last January, and several tests have since taken place at different locations in the country. Being a 60 × 60 × 50 cm, 85 kg “box,” the new equipment can be transported easily by car (see Figure 5). In addition to using the P-18 antennas, the HDF also allowed testing of the new system coupled to the only available high gain Oborona array that is still operational at one of Hungary’s radar sites. In the future, a new antenna design allowing for monopulse measurement is likely to be developed to solve current azimuth-accuracy and resolution shortfalls.
Though results of the testing are encouraging — and even the NATO Research and Technology Organization has relayed good feedback to the developers — the modernization project does not currently have a dedicated funding from the Hungarian MoD. Ongoing work is being financed by the Technology Agency, Sagax, and by some general centralized research and development (R&D) funds. To date, total investment has not exceeded, as one developer put it, “a couple of million Hungarian Florints” — under $10,000. In parallel, the Technology Agency has a project for the development of bi- and multi-static radar systems that would use VHF radars as well. After drawing up the concept, evaluation will start in 2006. Again, researchers decided to use two trusty P-18s: one as a transmitter and the other as a receiver. A new synchronization unit controls the sector sweeps and the triggering of the radars based on highly accurate Global Positioning System relative-position data and timing. In the current phase, the project managers plan to use unmodified P-18s to confirm the overall feasibility of the concept, but in the longer term the new metric radar could be used — or at least the developers hope so. This would make it easier to connect these sensors into a highly efficient and redundant, multi-static network.
Whether these R&D efforts will ever come to fruition is an open question, as Hungarian defense spending was cut by a third in 2004 and the country ranks last among NATO countries in terms of percentage of gross domestic product spent on armed forces. The other big question is whether the Hungarian radar community has enough lobbying power to ensure VHF frequency allocation beyond 2008, when the currently valid license to radiate in the metric band will expire.
Zord Gabor Laszlo is a journalist with the Magyar Nemzet conservative daily, Hungary, where he works on defense and security issues at the foreign desk. He graduated as a historian in 2001 from Miskolc University, where he wrote his thesis on Cold War reconnaissance flights and incidents. He started to research and write on military aviation as soon as he began his internship at the Uj Magyarorszag daily in 1995. Since then, he has written for the Hungarian aviation magazines and is a contributor to the Journal of Electronic Defense and eDefense Online.
