HP 492A Operating And Service Manual Download Page 1

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Summary of Contents for 492A

Page 1: ...HP Archive This vintage Hewlett Packard document was preserved and distributed by www hparchive com Please visit us on the web Scanned by on line curator Tony Gerbic For FREE Distribution Only ...

Page 2: ...HEWLETT PACKARD COMPANY 4 2A 4 4A TRAVELING VVAVE AMPLIFIER ...

Page 3: ...44 2 OPERATING AND SERVICE MANUAL MODEL 492A AND MODEL 494A SERIALS PREFIXED 010 TRAVELING WAVE AMPLIFIERS Copy gh HEWLETT ACICA D COM ANY 1962 lS01 AGE MILL ROAD ALO ALTO CALlFO NIA U S A Printed JAN 1962 ...

Page 4: ...PARTS 6 1 4 3 Magnet Power Supply 4 1 6 1 Introduction 6 1 4 5 Regulated Power Supply 4 1 6 4 Ordering Information 6 1 LIST OF ILLUSTRATIONS AND TABLES Number Illustration Title Page 4 3 Cutaway View ofaTWT Capsule and Magnet Showing the Important Elements 4 3 4 4 Cutaway View of an Encapsulated TWT 4 3 4 5 Simplified Circuit of a Constant Amplitude Variable Slope Sawtooth Generator 4 5 5 1 Top Vi...

Page 5: ...b shipping US volts 10 50 to 60 cps approximately 200 watts 63 Ib net 84 Ib shipping U5 volts 10 50 to 60 cps approximately 225 watts Accessories Furnished AC 16Q cable assembly AC l6Q cable assembly For Both Models Small Signal Gain 30 db minimum Meter Monitors Cathode current anode current helix current collector current Input Impedance 50 ohms swr less than 2 Output Internal Impedance 50 ohms s...

Page 6: ...ion generated within the amplifiers are at least 45 db below the output sig nal level and the noise figure is less than 30 db 1 3 The t Models 492A and 494A Traveling Wave Amplifiers amplify any type of rf signal cw swept sine modulated pulsed multiple signals on different frequencies etc A twt amplifier used as a modulator in conjunction with a signal generator can be used to amplitude modulate a...

Page 7: ...ck of complete infonnation may delay processing of yourcTiim Each tube manufacturer has his own warranty policy Copies of Individual Conditions of War ranty are available from your engineering representative or from Ihe He len Packard Company SHIPPING INSTIUCTIONS FROM rube Owner Company Address Tube type Tube serial No _ Tube mfr Use in Model _ Instrument serial no _ Date FOR FURTHER INFORMATION ...

Page 8: ...tection against large low frequency fields would require more shielding than is practical to in clude in the design 2 10 To operate connect the instrument to a 115 volt ac power source check and adjust rube operating 00144 2 currents as described in preliminary operating pro cedure section 1Il and connect to the external equip ment with coaxial cables terminated in standard UG 21D U type connector...

Page 9: ... not exceed maxi mum operating currents refer to table 3 1 Model 492A 494A 3 MAG C1RJD Il100 8 7 L S HELIX control is used to adjust for best broad band response position 5 or for maximum gain at anyone frequency 6 INPUT rf connector is where the rf signal to be amplified is coupled into the instrument 7 OUTPUT rf connector is where the amplified rf signal is coupled from the instrument 8 GRID MOD...

Page 10: ...begin to limit the electron density in the bunches 2 the energy transfer from the electron beam to the helix causes the beam velocity to decrease and gradually lose synchronism with the wave on the helix These effects become more pronounced as saturation is approached and cause the gain of the twt to decrease 3 6 HELIX CONTROL 3 7 The HELIX voltage control on the front panel maximizes the gain and...

Page 11: ...2A rr a 15 1 1 50 30 A VH HELIX VOLTAGE E o 0 VOLTS 4 5 6 7 8 G L 248 FREQUENCY KMC 49 4 A SMALL SIGNAL GAIN VH OPTIMIZED AT EACH FREQUENCY VH OPTIMIZED FOR BROADBAND OPERATION SATURATION POWER OUTPUT VH OPTIMIZED AT EACH FREQUENCY GAIN GAIN AT SATURATION POWER OUTPUT VH OPTIMIZED AT EACH FREQUENCY rr 15 1 1 25 45 c I 35 z 9 B VH HELIX VOLTAGE E g 0 VOLTS 7 8 9 10 II 12 G L 248 FREQUENCY KMC Figur...

Page 12: ...put signal carefully establish the opti mum rf drive grid bias and modulating signal amplitude for a given setup 3 22 For minimum distortion the twt grid voltage must not leave the linear region of the grid voltage vs rf output characteristic see figures 3 5 and 3 6 Also the rf drive must be adjusted so that the modu lation peaks are at least 2 db below saturation power DIRECTIONAL COUPLER LO L 2 ...

Page 13: ... 6 DB IODB 12 DB OUTPUT FREQUENCY HELIX VOLTAGE dJp MODEL 492 A TYPICAL MODULATION CHARACTERISTICS I I I T TT I i I 1 k r I I r I 1700 1600 I 1500 1400 0 et 1300 0 J 1200 0 0 11 00 t 1000 C J 900 0 J 800 J 700 z 600 500 0 400 0 300 200 100 0 10 5 o 5 10 15 20 25 30 35 40 45 50 55 G RID B I A S VOL T S G M 36 Figure 3 5 Typical Plot of Output Voltage vs Grid Voltage of a Model 492A 3 4 00144 2 ...

Page 14: ...000 Me HELIX VOLTAGE OPTIMIZED AT Eg O FOR EACH CURVE OUTPUT DB BELOW SATURATION OUTPUT AT Eg 0 800 fI t J l t 1 I 6 00 4 ____ 4 l ____ r __r___ _ __l 400 rl T ir 1 1 200 r d r 11 0 _ _ _ _ 1f_ _ _ _ ___l 1400 1200 0 0 J E I 0 1000 0 It z V J o J J 10 o 10 GRID 20 30 BIAS VOLTS 40 50 G M 37 60 Figure 3 6 Typical Plot of Output Voltage VB Grid Voltage of a Model 494A 00144 2 3 5 ...

Page 15: ...utput level d Determine the on off voltage ratio required in the rf output pulse 3 6 Model 492A 494A e Using the graph in figure 3 5 determine the magnitude of modulation pulse required to produce the desired on off ratio f Set the GRID BIAS control to obtain the voltage determined in step e Le the peak voltage of the modulating pulse The bias VOltage may be measured at the pin jack on the front p...

Page 16: ...o relay channels for retransmission production of mixer frequencies for radar and other microwave receivers etc G l I TI ME 3 34 HOMODYNE DETECTION Figure 3 7 RF Phase Shift Produced by Helix Modulation 3 32 With sawtooth modulation the desired output frequency shift F in figure 3 8 occurs during the sawtooth formatioJ time and is proportional to the rate of change of voltage During the sawtooth f...

Page 17: ...iagram of a Linear Homodyne Detection System INT SWEEP OSCILLOSCOPE MI XER 30 DB PAO T CONNECTOR TWT AMPLIFIER 20 OB DIRECTIONAL COUPLER SIGNAL GENERATOR 4 TO 8 KNC 0 USE hp MODEL 492 A 7 TO 12 4 MC USE hp MODEL 494 A USE APPROPRIATE DIRECTIONAL COUPLERS ATTENUATORS MIXERS ETC TO HELIX SLOPE MODULATED SAWTOOTH GENERATOR hp 202A FUNCTION GENERATOR M O P A MICROWAVE FREQUENCY MODULATION SYSTEM LD L ...

Page 18: ...y waveform before being applied to the traveling wave tube helix In this manner complex signals can be used to frequency modulate the signal applied to the twt and the center of the output fre quency will be fixed by the sawtooth repetition rate without slope modulation In no case should the p ase shift due to a single sawtooth cycle exceed 360 so that the amplification properties of the traveling...

Page 19: ...ALF WAVE RECTIFI ER SR2 VI V5A SR3 SERIES HELIX VOLTAGE REGULATOR MODULATOR I DOUBLER 6BQ6 V4 1126BQ7A REFERENCE ew I VOLTAGE I HELIX 0 OA2 STRAY CAPACITY c T1 V2 V5B CONTROL DISCHARGE I I POWER TUBE TUBE I i TRANSFORMER 6AU6 1 12 6BQ7A I W I I I el Y u HELIX e el Y I I ANODE J V3 o I GRID BIAS I BIAS eIY REGULATOR OB2 80 L 44B JF1 I SA F2 1 6A SR4 TIT MAGNET SI SUPPLY L J L o o N ...

Page 20: ... or as a 494A 7 12 4 gc by changing the twt Changing the tube type is no more difficult than replacing the twt with another tube of the same type see para 5 17 00144 2 4 8 The bias voltage for the twt is supplied by V3 and controlled by the GRID BIAS control on the front panel The grid of the twt is grounded through a 3900 ohm resistor and the voltage on the cathode is varied The circuit is arrang...

Page 21: ... FRON 500 V TO 1500 V DEPENDING ON TUBE TYPEl TjUl 1 OQO C M I l 1 g INPUT DIRECTIONAL COUPLER SINGLE WIRE HELIX OUTPUT DIRECTIONAL COUPLER CATHODE OV MODULATOR GRID I OV TO 50V TYPE N INPUT lh I I JACK fjjjjjjjjjfjjjjjjjjjjf ril1I I TYPE N OUTPUT JACK 8 0 t 0 I II n I Figure 4 2 Traveling Wave Tube and How It Works CD 1 1 1 _ o o I t ...

Page 22: ...s 4 3 and 4 4 Figure 4 3 Cutaway View of a Traveling Wave Tube Capsule and Magnet Showing the Important Elements OUTPUT COUPLER COAXIAL CONDUCTOR CATHODE OUTPUT Figure 4 4 Cutaway View of an Encapsulated Traveling Wave Tube 00144 2 4 3 ...

Page 23: ...y coupling refer to The Use of Quasi Static Mode Approximations in the Design of Slow Wave Structure Impedance Matches by Wayne E Raub dated August 1961 Manual number 27 3 Reprints available from Microwave Electronics Laboratory 4061 Transport Street Palo Alto California 4 15 GRID MODULATION 4 16 The signal being amplified in the traveling wave tube is amplitude modulated by applying the modula ti...

Page 24: ...ely independent and separately adjustable and the repetition rate should be adjustable over a wide range To frequency modulate an rf signal with a traveling wave tube amplifier it is necessary to mod ulate the slope or repetition rate of the sawtooth wave without affecting the sawtooth amplitude 4 24 A sawtooth generator having these character istics is shown in simplified form in figure 4 5 This ...

Page 25: ...e capacitor is discharged the grid bias on the blocking oscillator returns toward cutoff and at some value the 4 6 Model 492A 494A tube conducts sufficiently to start the blocking oscilla tor on another cycle of operation thus again recharg ing the capacitor 4 27 The amplitude of the output sawtooth waveform is adjusted by changing the regulated B to vary the charge placed on the capacitor The rep...

Page 26: ...or the equipment listed Table 5 1 Recommended Test Equipment Instrument Type Required Characteristics Use Mcx lel AC Voltmeter Voltage Range 1 0 mv to 1 volt Power supply ripple Mcx lel 4000 Voltage Accuracy 2 Spurious mcx lulation check Input Impedance 10 megohoms DC Voltmeter Voltage Range to 1000 volts Power supply Mcx lel 4108 Ohmmeter Voltage Accuracy 3 measurements Imput Impedance 100 megohm...

Page 27: ...ion V Figure 5 1 Model 492A 494A SR4 S2 f C2 C1 RT1 d SR2 SR3 i MEASU RE TWl 1t __ H E A T E R VOLTAGE R47 ir C8 r r 14 C3A B V3 5 V4 7 r O C 10 MP S 5558 Figure 5 1 Top View of Models 492A and 494A 00144 2 ...

Page 28: ...sule alignment screws The front alignment screws are shown in figure 5 2 and the rear alignment screws are shown in figure 5 3 e Remove twt plug from socket This plug is located on bottom of instrument Refer to figure 5 2 Grasp the rear of the capsule and carefully pull it out of the magnet 5 16 INSTALLATION AND ALIGNMENT To install and align a traveling wave tube capsule proceed as follows a Hold...

Page 29: ...94A PLUG I 0 UTPUT RF CABLE FRONT ALIGNMENT SCREW Figure 5 2 Bottom View Looking Towards the Front Panel of Models 492A and 494A REAR ALIGNMENT SCREW INPUT _ RF CABLE COLLECTOR LEAD TWT CAPSULE MP S I020 REAR ALIGNMENT SCREW 5 4 Figure 5 3 Rear View of Models 492A and 494A 00144 2 ...

Page 30: ...hould be less than 1 volt rms If these measurements do not reveal the cause of the trouble check the align ment of the twt in the magnet See paragraph 5 16 00144 2 Section V Paragraphs 5 23 to 5 29 5 24 CHASSIS HELIX CONTROL 5 25 The chassis Helix control R25 determines the range of the front panel HELIX control by govern ing the output voltage of the regulated power supply This adjustment should ...

Page 31: ...2 Cathode current high High anode VOltage Adjust anode voltage Para 5 26 Gassy twt Replace capsule Para 5 12 Anode current high Low helix voltage Adjust chassis helix voltage Para 5 24 Replace V5 Table 5 2 Gassy twt Replace capsule Para 5 12 High anode voltage Adjust anode voltage Para 5 26 Helix current high Misalignment of the twt Align capsule Para 5 16 Collector current Low or no twt magnet cu...

Page 32: ...4A proceed as for Model 492A except generator to be used in figure 5 4 to have a frequency range from 7 to 12 4 gc and the test should be made at these frequencies b Set generator to 6 gc in cw operation c With generator output power turned off adjust the twt HELIX control for a maximum dbm indication on the 43OC Record this reading 5 36 OUTPUT POWER CHECK 5 37 For Model 492A proceed as follows a ...

Page 33: ...ND SPURIOUS MOOULATIO CHECK 5 43 For Model 492A proceed as follows a Connect test setup as shown in figure 5 5 b Set the generator to 8 gc and to square wave modulation 1000 pps 5 8 c Set the twt HELIX control to position 5 and position the GRID BIAS control to full counterclockwise d Adjust the generator attenuator until the output is indicated as a 20 db on the 4000 e Switch the generator to cw ...

Page 34: ...ERLINED VOLTAGES ARE FOR hp MODEL 494A VOLTACE RANCE WHEN FRONT PANEL HELIX A21 IS VARIED BETWEEN LIMITS VOL TACE RANGE WHEN CHASSIS HELIX CONTROL RlS IS VARIED BETWEEN LIMITS 1 RESISTANCE IN QHMS UNLESS OTHERWISE NOTED 4 WHEN REPLACING V6 ADJUST i l l AS REQUIRED TO OBTAIN THE CORRECT HEATER VOLTAGE FOR v6 5 HEAVY 90X INDICATES FRONT PANEL ENGRAVING OK V3 C l f OB2 047 f SOl cw BIAS RECULATOR 1 1...

Page 35: ...ode delay line device signaling lamp misc electronic part F FL J K L M fuse filter jack relay inductor meter REFERENCE DESIGNATORS P plug Q transistor R resistor RT thermistor S switch T transformer v vacuum tube neon bulb photocell etc W cable X socket XF fuseholder XV tube socket XDS lampholder bandpass bwo backward wave oscillator c carbon cer ceramic cmo cabinet mount only coef coefficient com...

Page 36: ... 490A 82 Cathode Bypass Assembly O 002 j Lf DS1 2140 0009 Lamp incd 6 BV O 15 amp 47 F1 2 2110 0005 Fuse cartridge 1 6 amp s b J1 1250 0083 Connector BNC female J2 3 nsr part of V6 J4 1250 0083 Connector BNC female J5 1251 0073 Jack telephone tip for single conductor J6 1251 0027 Connector female L1 9110 0019 Choke 1 H M1 1120 0060 Meter ammeter P1 8120 0015 Power cable P2 thru P5 Not Assigned R1 ...

Page 37: ...omp 4 7K ohms 1O 1W R32 0687 1051 fxd comp 1M 10 1 2 W R33 0687 4741 fxd comp 470K ohms 1O 1 2 W R34 0690 6821 fxd comp 6800 ohms 1O 1 W R35 36 0690 3341 fxd comp 330K ohms 1O 1 W R37 thru R40 492A 26A fxd ww1 50 ohms R41 0690 1041 fxd comp lOOK ohms 10 1W R42 43 Not Assigned R44 0690 3921 fxd comp 3900 ohms 10 1 W R45 0693 1211 fxd comp 120 ohms 10 2 W R46 Not Assigned R47 0693 4701 fxd comp 47 o...

Page 38: ...3 1952 0009 encap TWT 494A only includes 12 3 MISCELLANEOUS G 74D Knob METER SELECTOR switch G 74N Knob CATH COL 1200 0009 Socket tube 7 pin 1200 0020 Socket tube octal 1251 0044 Connector female and male contacts 1400 0084 Fuseholder 1401 0006 Clip tube plate and grid cer ins 1450 0027 Lamp holder bayonet type 3150 0005 Filter air 6X6 9161 0005 Solenoid Assembly if See introduction to this sectio...

Page 39: ... 2M lO 1 W 01121 GB 1521 1 1 0690 2231 fxd comp 22K ohms 10 1 W 01121 GB 2231 1 1 0690 2251 fxd comp 2 2M 10 1W 01121 GB 2251 1 1 0690 2731 fxd comp 27K ohms 10 1 W 01121 GB 2731 1 1 0690 3341 fxd comp 330K ohms lO 1 W 01121 GB 3341 3 1 0690 3921 fxd comp 3900 ohms 1O 1 W 01121 GB 3921 1 1 0690 3941 fxd comp 390K ohms lO 1 W 01121 GB 3941 2 1 0690 4701 fxd comp 47 ohms 10 1 W 01121 GB 4701 1 1 069...

Page 40: ...100 0044 var comp lin 50K ohms 10 01121 JA1N0565503UA 2 1 2100 0133 var comp 200K ohms 20 2 W 11237 95CV 1 1 2110 0005 Fuse cartridge 1 6 amp s b 71400 MDL1 6 2 20 2140 0005 Lamp incd 6 8V 0 15 amp 47 24455 47 Frosted 1 1 3100 0055 Switch rot 4 pole 2 pos 76854 47809 F2 1 1 3100 0099 Switch rot 1 sect 4 pos 76854 161711 H1 1 1 3101 0003 Switch tog DPST 88140 8908K434 1 1 3140 0010 Motor AC 73793 G...

Page 41: ...evice Corp Hawthorne Calif a7 9 1 3 Rhelm Semiconductor Corp Mountain View Calif 07980 Boonton Radio Corp 800nton N J 08145 U S Engineering Co los Angeles Calif 083 5 B Burge Battery Co Niagara Falls Ontario Canada oB71 7 Sloan Company Burbank Calif 0871 8 Cannon Electric Co Phoenix Div Phoenix Aril a8 7 9 2 CBS Electronics Semiconductor Operations Div of C B S Inc Lowell Mass Babcock Relays Inc C...

Page 42: ...Mass K F Development Co Redwood City Calif Minneapolis Honeywell Regulator Co Micro Switch Division Freeport III Universal Metal Products Inc Bassett Puente Calif Sylvania Electric Prod Inc Semiconductor Div Woburn Mass Robbins and Myers Inc New York N Y Stevens Mfg Co Inc Mansfield Ohio lnsuline Van Norman Ind Inc Electronic Division Manchester N H Raytheon Mfg Co Industrial Components Div Receiv...

Page 43: ...na l OV Stock No 1880 0003 SR4 Change to rectifier metallic 620 rna l30V tStock No 1882 0007 Page 3 1 Table 3 1 Change HELIX CU RENT to read Table 6 1 VI Change descrip ion to tube clectro l 6BG6G Table 6 2 iStock o 0690 1521 Change description to fxd comp 1500 ohm IO o 1W 1j Stock No 1923 0026 Change description to tube electron 6BG6G Under lo tlSCELLA1 EOUS change Stock 1 0 1401 0084 to 1400 008...

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