1. PURPOSE AND SCOPE

a. Purpose. The purpose of this text is to provide the reader with an overall knowledge of the target-tracking radar and with a detailed knowledge of the target-tracking radar synchronizer, r-fand antenna system, transmitter, and receiving systems.

4. SYSTEM FUNCTIONING AND INTERRELATIONSHIP

a. Synchronizing system.

1. The synchronizing system synchronizes the timing of the transmitter pulse with the various range determining and sweep circuits in the target-tracking radar. This system determines the repetition rate (prf) of the radar. To do this, the synchronizing system generates two timing pulses; the sync pulse and the preknock pulse. The sync pulse is applied to the transmitting system and determines the triggering time of the magnetron. The preknock pulse is applied to the presentation system for triggering the sweep circuits, and to the target ranging system for triggering the range determination circuits.

2. The target-tracking radar is used in conjuction with the acquisition radar for target designation and acquisition. For this reason, the radars must be synchronized. This is done by triggering the synchronizing system of the target-tracking radar with the acquisition preknock pulse from the acquisition radar.

b. Transmitting system. The transmitting system generates high-power r-f pulses at a frequency variable between 8,500 and 9,600 megacycles. The sync pulse from the synchronizing system is applied as the input to the trigger generator in the transmitting system. The trigger generator output is applied to a modulator that converts the high voltage from a high-voltage d-c power supply into a series of distinct, 0.25-microsecond pulses. One of these pulses is generated each time the synchronizing system furnishes a sync pulse. These modulator pulses are applied to a magnetron which oscillates for the uration of each pulse; thereby, generating the high-power r-f signal. The magnetron output is fed by waveguide to the r-f and antenna system.

c. R-F and antenna system.

1. The r-f and antenna system radiates the high-power r-f energy generated in the transmitting system into space and receives the energy that is reflected back to the antenna when the radar beam contacts a target. It is mainly in the r-f and antenna system that this radar differs from conventional radars. A monopulse system is used to obtain target position information. In most conventional radars, lobe switching or conical scanning is used to obtain target position information, and several pulses must be used to determine the target azimuth and elevation. In the monopulse system, target position data is obtained each time a pulse is transmitted, reflected from the target, and received. This system has 2 pairs of radiating horns or feedhorns (see fig 4-1) and compares the amplitude of a single returned pulse as it appears in the 4 feedhorns. By finding the sum of the differences in the signal strength received by the upper pair of horns and the difference in signal strength received by the lower pair, an azimuth error signal is obtained. Similarly, an elevation error signal is obtained by subtracting the sum of the received signal strength of the upper feed-horn pairs from the sum of the received signal strength of the lower feedhorn pair. The azimuth and elevation error signals generated are used by other systems of the radar to keep the antenna on the target.

2. The r-f energy in the transmitting system is conveyed by waveguide and accessory equipment in the r-f and antenna system to a metal lens antenna, where the energy from the four feedhorns is radiated in a narrow beam according to a predetermined pattern. The energy reflected from a target is received by the same lens antenna, and after being broken into azimuth and elevation error components, and a sum signal in the r-f system, is conveyed to the receiving system. The r-f and antenna system uses an arrangement of ATR (antitransmit-receive) and TR (transmit-re'ceive) tubes to provide transmit-receive switching of the respective pulses. This system also contains an AFC (automatic frequency control) directional coupler which extracts a sample of the transmitted pulse for generating an automatic frequency control (AFC) signal. This AFC signal is applied to the local oscillator as a control signal to keep the frequency of the local oscillator 60 me above the transmitter frequency. An additional r-f'pulse is extracted by a second directional coupler for power monitoring purposes.
   

e. Ranging system (TM 9-5000-19).

1. The ranging system measures the time delay between the transmission of the r-f pulse and the reception of the target echo. Since the range of the target is proportional to the time interval between the transmission of the r-f pulse and the reception of the target echo, measuring the time interval determines the range. Three means are provided for controlling the range determining circuits: manual, aided, and automatic . Manual and aided ranging are done through manual ranging controls (handwheels) and are used for acquiring a target; and for target tracking when automatic tracking is impossible. Automatic tracking of the target in range provides smooth range data for the computer. The circuits of the ranging system are triggered by the preknock pulse and transmitted pulse applied from the synchronizing system and transmitting system. These pulses indicate to the ranging system the time of transmission of the r-f pulse and, in effect, determine the zero time of the range scale.

2. Acquisition of a designated target in range is done by the ranging system and the acquisition radar functioning in conjunction with each other. The ranging system furnishes two signals to the acquisition indicators; a track range gate (TRGA) and an acquisition track range mark (QTRMK). The QTRMK is also sent to the target range slew control unit. There, this signal, representing the range of the target-tracking radar, is compared with the range designated by the acquisition radar. The difference between the target-tracking radar range and the designated range is detected by the range slew control unit which causes the ranging system of the target-tracking radar to slew in or out, in range, to the designated range.

3. To enable the presentation system to generate a short sweep that is centered around the radar range point, the ranging system furnishes a 3-microsecond expansion pulse. The ranging system also supplies the mixed range video and range notch signals for the indicators in the presentation system. For the angle error detector circuits in the receiving system to determine the antenna pointing error of the target being tracked, the ranging system supplies it with a track receiver gate. This signal distinguishes the target video signal from all other video signals.

f. Antenna positioning system (TM 9-5000-20). The function of the antenna positioning system is to correct the antenna pointing error of the target being tracked. As in range tracking, three modes of operation are provided for controlling the antenna position in azimuth and elevation: manual, aided, and automatic. Manual and aided tracking are done through the appropriate hand-wheels and are used for acquiring a target. Automatic tracking of the target in azimuth and elevation provides smooth coordinate data for the computer. In this mode of operation, the antenna is steered in accordance with d-c azimuth and elevation error signals supplied by the receiving system. The antenna positioning system can acquire a target in azimuth in accordance with azimuth data designated by the acquisition radar. The system can also acquire a target in both azimuth and elevation in accordance with remote position data supplied by a fire direction center (FDC).

g. Presentation system (TM 9-5000-19)

1. The presentation system is the visual link between the target-tracking radar and the tracking console operators. It is made up of three radar indicators and the associated circuits necessary to display visually the information generated by other functional systems of the tracking radar. The three indicators are: range indicator, azimuth indicator, and elevation indicator. Two additional indicators, the precision indicator (PI) and the plan position indicator (PPI), also appear on the target-tracking console with the other indicators. However, these two are not considered part of the target-tracking radar presentation system and are covered in the acquisition radar functional description ( TM 9-5000-9). The PPI displays the acquisition video and the target-tracking radar slant range and azimuth with an electronic cross. The acquisition designation information is shown with a range circle and an azimuth mark. The precision indicator or B-scan presentation displays an area around the electronic cross and covers a sector 5,000 yards in range and 30° in azimuth.
   

2. The range indicator uses a modified A-scan presentation and displays a 100-yard movable notch in which the operator centers the target. A 500-yard section centered about the notch is expanded for more accurate tracking. The 500-yard expanded section is also displayed on the azimuth and elevation modified A-scan presentations. The sweep length on the three indicators in continuously variable from 20,000 to 100,000 yards with the 500-yard expanded section occupying a constant proportion of the total visible sweep length. Elevation and azimuth manual tracking is performed by pip canceling. Coarse and fine dials displaying the coordinate information are also included and appear on the front panels of the appropriate indicators.

3. The indicators in the presentation system are synchronized in the radar by the target preknock pulse from the synchronizing system. The azimuth and elevation video signals for the indicators are applied from the receiving system, while the mixed range video and notch and the expansion pulse signals are applied from the ranging system.

h. Testing, monitoring, and calibrating system (TM 9-5000-12). The testing, monitoring, and calibrating system is made up of test equipment built into the radar to make sure that the radar operates properly and with maximum efficiency. Included in this system are units whose functions are: to monitor and to adjust the angle error detectors of the receiving system; to monitor crystal currents, i-f main amplifier bias voltage, and i-f signal levels in the receiving system; to calibrate the ranging system; to provide a means for checking the operation of the magnetron and its associated waveguide in regard to power; and to perform other important functions. The functions are discussed in detail in TM 9-5000-12.

The synchronizing system generates timing signals to synchronize the transmitter pulse with the various range indicating and sweep circuits in the target-tracking radar. The synchronizer provides two 40-volt, 2-microsecond positive pulses for this purpose. The first of these pulses is the preknock pulse which is made available to the sweep and range indicating circuits approximately 23.5 microseconds before the transmitter is triggered. The second output pulse is the synchronizing pulse, which triggers the transmitter. The 23.5-microsecond delay between the preknock and the synchronizing pulses is necessary to begin the functions of the sweep and range unit early enough to permit their use in measuring down to zero range, which corresponds to the leading edge of the transmitted pulse. To allow transmission of accurate acquisition data from the acquisition radar, the target-tracking radar synchronizer is synchronized to the acquisition pulse repetition frequency by the acquisition preknock pulse. This is done with the INT-AUTO switch S1 in the AUTO position. With switch SI in the INT position, the target-tracking radar operates independently as a free-running synchronizer. The operation of the preknock pulse in the target ranging and presentation systems is discussed in detail in TM 9-5000-19. The operation of the synchronizer pulse in the transmitting system is discussed in detail in chapter 3 of this text. The synchronizing system of the target-tracking radar is acquisition and target track synchronizer GS-15616. This unit is located in target-tracking console assembly GS-15513, figure 1-16.

a. Inputs and outputs.

1. The acquisition preknock pulse (positive, 10-volt, 2-microsecond pulse) is an input to target a synchronizer utilized in synchronizing the operation of the target-tracking radar with the acquisition radar. This is necessary to accurately transfer targets from the acquisition radar to the target-tracking radar.

2. The target preknock pulses (positive, 40-volt, 2-microsecond) initiate the action of the timing, ranging and sweep circuits. Due to the 23.5-microsecond delay in the synchronizer and a 0.9-microsecond system delay, this occurs 24.4 microseconds prior to firing the transmitter.

3. The target preknock pulse (positive, 40-volt, 2-microsecond)is used to trigger the transmitting system and the i-f test unit.

4. The test pulse (6-volt, 7-microsecond) output, used in the acquisition system to aline the moving target indicating (MTI) system, is not used in the target-tracking radar.

b. Components. The components of the synchronizing system are: amplifier VI, blocking oscillator V2A, pulse amplifier V3A, sync delay network Zl, switch tube V3B, amplifiers V5A and V5B, and synchronizing pulse blocking oscillator V2B.

c. Output distribution (fig 2-1).

1. The target synchronizing pulse (40-volt, 2-microsecond) is applied to the following:
   1. The target trigger generator, where it triggers a single-swing blocking oscillator.

   2. The i-f test unit, where it triggers circuits that develop an i-f pulse for adjusting the target-tracking radar receiving system.

2. The target preknock pulse (40-volt, 2-microsecond) is applied to the following:
   1. The range unit assembly, where it triggers circuits that develop the tracking range mark (TRMK), tracking range gate (TRGA), and the acquisition tracking range mark (QTRMK).

   2. The delay amplifier, where it triggers a flip-flop multivibrator and makes possible a comparison of range settings of the acquisition and tracking radars possible. Slewing of the tracking range to the acquisition range is dependent upon this comparison.

   3. Three target-tracking sweep generators, where it initiates sweeps for the target-tracking indicators.

   4. The video error signal unit where it triggers circuits to permit pip canceling on the target-tracking indicators.

   5. The test delay unit, where it triggers circuits that develop an artificial target which may be varied in range to check and adjust various circuits of the target-tracking radar.

a. Driver VI. Tube VI amplifies the preknock pulse from the acquisition radar when INT-AUTO switch SI is in the AUTO position. With switch SI in the INT position, the acquisition preknock pulse is grounded through a resistor and there is no input to the driver. The amplified acquisition preknock pulse from the driver synchronizes the blocking oscillator with the acquisition radar pulse repetition frequency (prf).

b. Blocking oscillator V2A. Tube V2A, with INT-AUTO switch SI in the INT position, is a free-running blocking oscillator. With the switch in the AUTO position, preknock pulses from the acquisition radar are amplified by VI and drive the blocking oscillator. The acquisition preknock frequency is slightly higher than the free-running frequency of the blocking oscillator. The blocking oscillator locks to the frequency of the preknock pulse, giving an output which is synchronized to the prf of the acquisition radar. The positive output pulse goes to the range and presentation circuits as the track preknock pulse and to the delay section of the synchronizer where the 23.5-microsecond delay between the preknock and the synchronizer pulse is introduced. The preknock pulse is a 40-volt pulse and is about 2 microseconds in duration.

c. Tripper V3A. Tube V3A inverts the positive preknock pulse and the negative output pulse triggers monostable multivibrator V4 and starts delay network Zl in the delay pulse generator.

d. Multivibrator V4. Tube V4 is a monostable multivibrator used as a switch to start operation of the Zl delay network. The multivibrator is triggered by the target preknock pulse. The delay time of the multivibrator is great enough to allow network Zl to discharge. After delay network Zl discharges , the multivibrator returns to its quiescent state until triggered by the next preknock pulse.

e. Delay pulse generator V3B and Zl. Delay network Zl is an R-C network in which the discharge time from preknock is less than the period of the multivibrator. For this reason, jitter and variations of time delay, which are inherent in the monostable multivibrator, have no effect on the succeeding circuitry. Network Zl controls the on-off time of diode V3B and produces a 23.5 microsecond, negative, square pulse at its output. The leading edge of the square pulse coincides in time with the track preknock pulse, and the trailing edge is set by adjustment of the network discharge time.

f. Delay pulse amplifier V5A. Tube V5A amplifies the output from V3B and the amplified pulse is applied to the grid of V5B.

g. Driver V5B. Stage V5B is the driver for synchronizing pulse blocking oscillator V2B. Pulse transformer T3 in the plate circuit of V5B differentiates the output of V5B so that V2B will be triggered on the trailing edge of the delayed pulse.

h. Synchronizing pulse blocking oscillator V2B. Tube V2B is triggered by the trailing edge of the differentiated delayed pulse from V5B. The blocking oscillator action provides the 40-volt, 2-microsecond synchronizing pulse which triggers the transmitting system. Because of cable delays of approximately 0.9 microsecond, the transmitter is triggered about 24.4 microseconds after preknock.

8. OVER-ALL SYSTEM BLOCK DIAGRAM

a. General.

1. The target-tracking radar transmitting system provides the r-f and antenna system with high-energy radio frequency in the form of repetitive pulses. The repetition rate of 1,000 pulses per second is determined by the synchronizing system. The 0.18-microsecond duration of each pulse is determined by the transmitting system itself. Each pulse, in turn, is applied to the r-f and antenna system with a normal peak power of approximately 200 to 400 kilowatts, at a radio frequency which is variable within the range of 8,500 to 9,600 megacycles. The target-tracking radar transmitting system is made up of track trigger generator GS-15460, slipring assembly GS-15536, track modulator GS-15461, a pulse transformer, and the 5780 magnetron with its tuning drive and associated circuitry. Only a portion of the slipring assembly is used in the transmitting system. All components of this system are located on the target antenna trailer GS-15520.
   

2. Figure 3-1.1 is a block diagram of this system. The trigger generator receives the 40-volt, 2-microsecond pulse from the synchronizing system at the rate of 1,000 pps, and produces a 230-volt, 4-microsecond pulse, which is applied to the track modulator. The track modulator, with its associated high-voltage power supply, produces from this pulse a 6,500- to 8,500-volt, 0.25-microsecond pulse. This pulse is transferred through sliprings to the pulse transformer, which steps up the pulse to 30 to 35 kilovolts, and applies it to the magnetron. Each pulse causes the magnetron to oscillate at the frequency to which it is tuned within the 8,500- to 9,600-megacycle range. The output of the magnetron is fed by waveguide to the r-f and antenna system.

b. Trigger generator.

1. Location. The trigger generator is located in the equipment enclosure (roadside) of the target-tracking radar antenna.
2. Purpose. The trigger generator receives the sync pulse from the target synchronizer and builds it up enough to trigger the modulator.
   

3. Inputs. There is one input; a 40-volt, 2-microsecond positive sync pulse from the target synchronizer.

4. Outputs. One output is supplied. This is a 230-volt, 3- to 5-microsecond, positive trigger pulse, which is applied to the modulator.

5. General operation. The sync pulse is applied to a single-swing blocking oscillator circuit which increases the duration time to from 3 to 5 microseconds and amplifies the pulse from 40 volts to 230 volts by doubling the amplitude of the blocking oscillator output through transformer action. The 230-volt, 3- to 5-microsecond pulse is then applied to the modulator.

c. Modulator.

1. Location. The modulator is located in the antenna equipment enclosure, next to the trigger generator.

2. Purpose. The modulator generates and shapes the pulse that will cause the magnetron to oscillate and generate an r-f pulse.

3. Inputs. This chassis has one input; a 230-volt, 3- to 5-microsecond pulse from the trigger generator.

4. Outputs. The single output is the negative, 6,500- to 8,500-volt, 0.25-microsecond pulse which is applied to the primary winding of the pulse transformer.

5. General operation. This unit is composed chiefly of a pulse-forming network (Zl), an input thyratron switch tube, a charging diode, and a reverse-current diode. The Zl network is charged by voltage from the high-voltage power supply and operates as a d-c resonant charging circuit. The charge on the pulse-forming network is trapped by the action of the charging diode. The thyratron switch tube, when triggered, causes the pulse-forming network to discharge and supply the pulse which, after amplification, will fire the magnetron. The reverse-. current diode prevents the pulse-forming network from acquiring a negative charge, thereby permitting it to start charging from the same level at the beginning of each charging cycle. A reverse-current meter in the circuitry will indicate the value of reverse current (average 20 ma) and give an indication of magnetron malfunction by indicating when reverse current has become excessive (over 30 ma).

d. Sliprings.

1. Location. The sliprings are on the trunnion assembly of the tracking radar antenna.

2. Purpose. The sliprings provide electrical continuity between the rotating parts of the antenna assembly and the stationary parts.

3. Inputs. The input from the transmitter is the negative 6,500- to 8,500-volt, 0.25-microsecond pulse from the modulator.

4. Outputs. The 6,500- to 8,500-volt pulse is conducted through the slip-rings and is applied to the pulse transformer.

5. (5) General operation. The sliprings are a group of 89 inner ring segments. A like number of contactor arm assemblies are mounted mechanically in a manner to maintain circuit contact with the rings at all times when the antenna traverses on its trunnion assembly. These assemblies maintain circuit continuity in a flexible manner. This permits passage of signals through the assembly without changing them.

e. Pulse transformer.

1. Location. The pulse transformer is in the track r-f unit near the magnetron.

2. Purpose. The pulse transformer receives the negative modulator pulse and steps it up without phase inversion. The stepped-up high-voltage pulse to the magnetron cathode is applied through bifilar windings. This prevents a great potential difference from existing between cathode and heater and probable heater breakdown.

3. Inputs. The pulse transformer input is the negative 6,500- to 8,500-volt, 0.25-microsecond pulse which is applied to the primary winding terminals from the modulator.

4. Outputs. The output of the pulse transformer is a negative 30- to 35-kilovolt, 0.25-microsecond pulse with a step in the leading and trailing edges. This pulse is applied to the magnetron cathode.

5. General operation. Transformer T4, the pulse transformer, is wound so that there is a step-up ratio from primary to secondary of 1:4. There is no phase inversion of the voltage output from the secondary as is normally encountered through transformer action. The secondary voltage is applied to the cathode of the magnetron. Bifilar winding averts the danger of a high potential difference existing between the cathode and heater causing possible arc-over and consequent heater breakdown. The bifilar winding design of the transformer is such that it places the same potential on the heater and cathode during the application of high-voltage triggers. When the high-voltage pulse is applied to the magnetron cathode, the magnetron will oscillate at the resonant frequency of the slug-tuned cavities.

f. Magnetron.

1. Location. The magnetron is mounted in the track r-f unit. With the cover removed from the target-tracking radar and the observer facing the lens assembly from the rear of the r-f unit, it is to the upper left of the assembly.
   

2. Purpose. The magnetron receives the output of the pulse transformer and oscillates at a frequency determined by the resonant size of its cavities. The size of the cavities is determined by the setting of the tuning slugs controlled by the tuning drive unit. It delivers an r-f output when triggered by the pulse transformer. This radio frequency is necessary to determine target information.
   

3. Inputs. The input to the magnetron (other than heater voltage) is the negative 30- to 35-kilovolt, 0.25-microsecond pulse from the pulse transformer.
   

4. Outputs. The output of the magnetron is an r-f pulse; 0. 18 microsecond in duration; peak power, 200 to 400 kilowatts; frequency range, 8,500 to 9,600 megacycles.
   

5. General operation. Application of the pulse from the transformer to the magnetron cathode causes electron flow from the cathode toward the plate (anode). This electron flow will bring about oscillations in the slug-tuned cavities of the magnetron. These oscillations produce an output pulse whose frequency is determined by the cavity size and whose output power is on the order of 200 to 400 kilowatts. The magnetron' s frequency range is 8,500 to 9,600 megacycles per second. The duration of this transmitted pulse is 0.18 microsecond.
   

g. High-voltage power supply.

1. Location. This unit is located in the upper left corner of the equipment enclosure (roadside).
   

2. Purpose. Its supplies a high-potential d-c voltage output to charge the pulse-forming network, Zl, in the modulator.
   

3. Inputs. The inputs are 120-volt, 3-phase, a-c voltages from the system a-c distribution.
   

4. Outputs. The output is a 6,500- to 8,500-volt d-c voltage applied to the tracking modulator.
   

5. General operation. This power supply is a full-wave type rectifier which has a-c inputs. A transformer and two diodes rectify and amplify this voltage into a high d-c potential. It is applied to the modulator for charging the pulse-forming network (Zl). The high-voltage d-c potential is determined by the setting of the high-voltage supply control on the control panel of the target-tracking radar console. This portion of the transmitting system wil not be discussed in this text but is covered in detail in TM 9-5000-17.

h. Magnetron tuning drive.

1. Location. This circuitry is located in the track r-f unit of the antenna mount assembly. Controls are located in the r-f unit and on the target-tracking console assembly.
   

2. Purpose. The tuning drive assembly positions the tuning slugs in the cavities of the magnetron so as to adjust the physical size of the cavities for resonance at the desired frequency of transmission.
   

3. Inputs. The inputs consist of a-c driving and motor excitation voltages.
   

4. Outputs. The output of the tuning drive is mechanical slug positioning.
   

5. General operation. There are two FREQUENCY INCREASE-DECREASE switches associated with the tuning drive. One is on the target console control panel in the radar control trailer and the other is on equipment panel A of the track r-f unit at the antenna. These switches are spring-loaded to keep them in a midposition (neutral). When either is pressed to the DECREASE position, voltage is applied to the driving motor in such phase that it causes the slug-positioning mechanism to withdraw the slugs and increase the cavity size, which decreases the frequency. If either switch is operated to the INCREASE position, the tuning drive motor will be driven in the opposite direction, resulting in a positioning of the slugs deeper into the cavities and a decrease in cavity size results in an increase of magnetron frequency of oscillation. A FREQUENCY meter, located on the control panel at the target-tracking console, is connected in the tuning drive circuitry in such a manner as to indicate relative frequency of the magnetron tuning.
   

c. Detailed circuit discussion (fig 3-3).

1. Sync pulse amplifier. The 1-2-3 (VIA) section of VI and its associated components make up the sync pulse amplifier (driver). A positive sync pulse entering jack Jl appears as a positive pulse on the grid of VIA by the transformer action of transformer T3. This pulse entering jack Jl is the synchronizing pulse. Tube VIA is normally cut off with a fixed -31 volts applied to the grid from voltage divider R4-R6. When the positive pulse from terminal 6 of transformer T3 appears on the grid, tube VIA conducts heavily and produces a large negative pulse on terminal I of transformer Tl. Resistor Rl3 is a grid limiting resistor.
   

2. Blocking oscillator. The 6-7-9 (VIB) section of VI and its associated circuit components make up the blocking oscillator. Voltage divider RI-R2 supplies approximately -31 volts to the grid of VIB. This fixed bias voltage normally cuts off the tube. The negative pulse from VIA on terminal I of transformer Tl appears as a positive pulse on terminal 4 of transformer Tl. Thus, the grid of VIB goes positive, permitting the tube to conduct. When the tube conducts, still more current flows through winding 1-2 of transformer Tl, which causes terminal I to become more negative. This, in turn, produces a more positive pulse on terminal 4 of transformer Tl and the grid of VIB, making the tube conduct more heavily. When the plate of VIB reaches its maximum conduction of current (saturation), the field produced in transformer Tl starts collapsing. This action causes a very large negative pulse to appear on terminal 4 of transformer Tl which immediately drives the grid bias beyond cutoff. The tube remains cut off (by the -31 volts appearing on the grid) until the next sync pulse is applied to the unit. This blocking oscillator produces a single cycle, and the action described is very rapid. The length of the pulse depends on the leakage inductance and distributive capacitance of transformer Tl. The large positive pulse (approximately 500 volts) appearing at terminal 6 transformer Tl is applied to the grid of tube V2.
   

3. Cathode follower V2. Cathode follower tube V2 consists of two triode sections connected in parallel. This tube isolates blocking oscillator VIB from the high-voltage pulses produced in the track modulator. Resistors R7, RIO, andR12 are parasitic suppressors. They prevent oscillations within the tubes. The large positive pulse appearing at terminal 6 of transformer Tl is applied to grids of V2 through resistors RIO and R12. This pulse causes the tube to draw plate current until the grid potential (and cathode potential) is equal to the plate potential. At this point, plate action by both grids raises the cathode well above plate potential. The action just described produces a positive 230-volt, 4-microsecond pulse across cathode resistor R9. This positive pulse is shunted across capacitor C5, because capacitor C5 does not have good high-frequency response. Capacitor C6 is a mica capacitor and has a very good high-frequency response. This parallel combination of capacitors C5 and C6 permits good reproduction of the pulse. The output pulse is passed through a coaxial cable to the track modulator. The cathode of V2 is connected to the filament so that the breakdown voltage rating between cathode and filament is not exceeded during the pulse period.
   

4. Component usage. Capacitors CIA, CIB, C2, C3, andC7, along with the 2-microfarad capacitor added by field change 367N» provide decoupling. Transformer T2 provides filament voltage for VI and V2. Resistors R5 and R8 dampen any ringing oscillations that may occur across the pulse transformers. Test point I (TPI) is for testing the bias voltage applied to the blocking oscillator. Test point 2 (TP2) is connected directly to the output of the unit and serves as a point at which to monitor the trigger pulse.
   

13. GENERAL

a. The r-f and antenna system radiates the r-f energy pulses into space from the transmitting system and receives the returned signals of these pulses reflected by a target. The direction finding and ranging operation is carried out by the r-f and antenna system using the monopulse principle described in paragraph 14, Introduction to Monopulse Radar. The r-f pulses are emitted in an extremely narrow beam by a lens-type metal antenna. The reflected pulses received at the antenna are applied to the monopulse waveguide plumbing which supplies three signals containing information necessary for ranging and automatic tracking of the moving target. The three signals applied to the receiving system are: (1) total strength of the received signal (or amplitude sum), (2) azimuth difference, and (3) elevation difference.

b. Another function of the r-f and antenna system is the transmit-receive switching used in coordinating the actions of the transmitting and receiving systems. The r-f and antenna system also provides sampling of the transmitted pulse that is used for automatic frequency control in the receiving system for power monitoring. The r-f and antenna system comprises the track waveguide assembly GS-15600, the track lens assembly GS-15645, four 6163 ATR boxes (tubes), three 6164 TR boxes (tubes), and two directional couplers. All of these components are located in the target track r-f unit GS-15598.