PRV-9 1RL19 / PATTY CAKE - Mobile radio altimeter

The PRV-9 radar (NATO name: PATTY CAKE) is a height finding radar operating in the "D/E" Band. In 1953, the PATTY CAKE height finder was produced by the Soviets. This radar did not follow the usual Soviet development pattern — because it was uniquely Soviet in design — not a copy of Western technology. This, as stated, was contrary to the pattern followed in the V-beam early warning radar (TOKEN) and fire-control radar (WHIFF) which were directly derived from Western radar technology. PATTY CAKE remained the sole Soviet operational height finder from 1953 to 1956. Although the Soviet Union and the Soviet satellites were still using U.S.-made and British-made radars, in addition to the Soviet-made copies of U.S. and British radars.

Western observations during the 1954 time period showed that the Soviets were developing a radar system that made concurrent use of two sets as a single unit. The most commonly used sets were GAGE (search finder) and PATTY CAKE (height finder). The advantages of this system, in relation to TOKEN, proved to be: less complicated installation; simpler maintenance and operation, and with increased range and height finding capabilities. The Soviets took this one step further by building radar installations with four radars. These radars were situated in pairs with Gage and PATTY CAKE comprising each pair. This appeared to represent a movement away from the mobile V-beam, TOKEN, to a static system of radar defense.

The PATTY CAKE is a predecessor to the PRV-10M PATTY CAKE mobile radar. Weapon systems associated with the PRV-9 include the S-25. The PRV-9 radar is also associated with GCI systems.

Due to the fact that the PRV-10 and PRV-11 radio altimeters did not fully meet the requirements of the ground forces air defense, in terms of mobility (a large number of transport units and a long deployment time), it was decided to develop a more mobile radio frequency altimeter PRV-9 ( OCR "Tilt-2"). The development was started at OKB-588 MGSNH (OKB Lianozovo Electromechanical Plant) in 1958. The Chief Designer was Lev Isaevich Shulman. In 1960, the PRV-9 radio altimeter passed state tests at the NIZAP GAU and then was put into service. In 1960, OKB-588 MGSNH, together with Scientific Research Institute-208 GKRE, began developing an automotive version of the altimeter - PRV-9A (chief designer of the altimeter L. I. Shulman) as an integral part of the mobile radar detection (rangefinder) "Armor" - P- 40D (1RL128D). Two modifications of the altimeter were developed:

• PRV-9A on the chassis of the KrAZ-214 car, which towed the 1E9 power station in the trailer;
• PRV-9B - based on the KRAZ-214 chassis without its own primary power sources, powered from a gas turbine power unit of a rangefinder.

The PRV-9A altimeter in 1962 passed state tests as part of the Bronya radar at the Donguz proving ground and was put into service, produced at Lianozovo Electromechanical Plant.

This radio altimeter differed significantly in the applied schematic and cost-effective solutions from the radio altimeters of the PRV-10 line - PRV-11 - PRV-13. The use of the 5-centimeter range allowed the use of an antenna of much smaller dimensions and weight, which accordingly made it possible to create less energy-intensive systems for its swing and rotation, abandoning the use of traditional 10-centimeter range receiving-transmitting cabin. The deployment and folding of the antenna with the use of built-in mechanization tools has been greatly simplified and reduced in time. In the transport position antenna column with antenna placed along the roof of the cab, while the upper part of the mirror on the hinges fell down . Due to the fact that the cross section of the waveguide was quite small, to increase the electrical strength of the waveguide path (gear), dried air was pumped into the hermetic path by increased pressure. For this purpose, an aggregate with the name "dehydrator" was used. A ferrite circulator is used in the antenna switch.

As is well known, in the traditional modulators with a long line drive and an ion switch, hydrogen filled thyratrons are used as a switch . To fill the volume of a thyratron balloon with hydrogen in the required concentration inside the balloon there is a gas generator, heated by electric current. It took about 7-8 minutes to heat up a TGI-700 type thyratron (4.5 minutes TGI-400), which determined such an important parameter as the radar on time.

A special feature of the construction of the PRV-9 transmitting device was the use of a magnetic modulator, which was not used in any radar either before or after the PRV-9 and PRV-16. Rejecting the use of an ion switch (a powerful gas-filled thyratron) was intended, apparently , to increase the reliability of the modulator, to reduce the modulator readiness time for operation, to reduce the mass-dimensional characteristics. The disadvantages of such a modulator include the inability to change the repetition frequency of the probe pulses (it was determined by the frequency of the supply AC voltage - 400 Hz), which causes difficulties in pairing with other radars and automatic control systems (including to eliminate mutual asynchronous interference). By the way, the diagnosis of failures in such a modulator was also difficult, practically only one method was used - the replacement of a suspicious element with a known good condition.

But since there were no such elements in the individual spare parts kit, the downtime during failures was significant and determined by the delivery time of the required item. In the PRV-9 for the first time was applied such a method of protection against targeted active interference as the restructuring of the carrier frequency of the microwave generator from pulse to pulse. For this, a new microwave magnetron was developed. When operating in passive interference protection mode, the transmitter operated at one of five preset frequencies. The receiving device is designed as a superheterodyne with double frequency conversion (to provide the necessary bandwidth of the receiving path). In the UHF receiving path, a traveling-wave lamp was traditionally used.

The first two local oscillators were used - depending on the radar operating mode, one of them was used with its own automatic frequency control system. In the protection against sighting active interference mode, the first local oscillator on the reflective klystron with an “instant” AFC was used, adjusting the local oscillator frequency during the duration of the probe pulse. In the mode of using the SDC (when operating under conditions of passive interference), the transmitter operated at one of the fixed frequencies and the first local oscillator on the klystron was used, in which the frequency was changed mechanically through an actuator with a small electric motor. This local oscillator possessed the time-frequency stability necessary for the operation of the coherent-pulsed equipment of the MTS system.

The equipment of the interperiod compensation (CPK) was built according to the traditional scheme on two subtractive potentialoscopes and constructively fit in one small typical unit. Moreover, the same equipment was used in the suppression of non-synchronous interference. The antenna mirror swung in a vertical plane with a single frequency swing mechanism, which is a gear reducer with an asynchronous three-phase electric motor. On the output shaft of the gearbox there was a crank connected through a mirror to the antenna through a thrust. The antenna column rotation system was a single-channel synchronous-tracking drive on selsyns (with an electric machine amplifier and an executive DC motor).

Indicator equipment was represented by a height indicator (on a CRT 35LM2V ) and a control indicator (on a CRT 8LO29I). The original scheme was the formation of elevation marks - 1-kilometer elevations were formed from 10-kilometer range marks. It allowed to do without special the pulse-forming cathode-ray tube of the IF-17, used in the PRV-10 - the PRV-13, which greatly simplified the layout of the height indicator and the indicator settings. The radio altimeter equipment was built on the elemental base of the first generation (using finger-mounted radio tubes using mounted mounting; transistors were used in power supply stabilizers).

Structurally, the radio altimeter is built very compactly and even elegantly. All equipment was placed in a trailer of very small dimensions. This small trailer was divided into three compartments by partitions. In the first (the entrance through the door on the side of the cabin) was placed the base of the antenna column, part of the antenna-waveguide path, electric motor amplifier (EMU) system antenna rotation. In the second, middle compartment, on the starboard side were placed the cabinets of the modulator, microwave generator and control system, control and protection. On the left side in the typical blocks were placed all the rest of the equipment, except for the height indicator cabinet. The height indicator cabinet was located in the third compartment. Individual spare parts were located in 2 and 3 compartments.

The height indicator could be removed from the cockpit to the control point of the unit for a distance of 300 meters. The power supply of the radio altimeter was carried out from the power supply unit AD-30 / T / 230-H-400 (30 kVA, 230 V, 400 Hz, 3 phases with insulated zero, based on the very reliable four-cylinder diesel engine YMZ-204G). As part of the power station 1E9, housed in a trailer based on the chassis 2-PN-6 are placedtwo units AD-30.

The unit could include an IPL-30 frequency converter (PSCH-30) in a metal casing (without a chassis). According to the operating experience, the charging reactors in the magnetic modulator and the ferrite circulator in the antenna switchboard turned out to be the least reliable . Diagnosing these failed items was very difficult.

In general, it was a fairly reliable radar, although its coverage area (as compared with PRV-11, PRV-13) was significantly more modest. In conclusion, the PRV-9 altimeter turned out to be so perfect structurally that it did not even carry out any military modifications, it also did not use among military rationalizers "popular". Even during the design work on the further development of this altimeter in the PRV-16, only three things could be added: the direction finding channel, protection from self-guided anti-radar projectiles and replace KrAZ-215 with KrAZ-255.