Summary of Contents for 120-E

Page 1: ...STRUCTION BOOK FOR MODEL 120 E FIELD STRENGTH METER IllfroELECTRON CS A DIVISION OF VITRO CORPORATION OF AMERICA 919 JESUP BLAIR DRIVE SILVER SPRING MARYLAND PRODUCERS OF NEM LARICE EQUIPMENT www amer...

Page 2: ...INSTRUCTION BOOK FOR MODEL 120 E FIELD STRENGTH METER Scanned and Prepared by Dale H Cook 919 Jesup Blair Drive Silver Spring Md A Division of Vitro Corporation of America www americanradiohistory com...

Page 3: ...llation 6 1 Battery Installation 7 2 Use of external power supply 7 3 Use of recording equipment 7 Operation 7 1 Checking battery voltages 7 2 Meter Calibration 8 3 Measuring signal strength 8 4 Opera...

Page 4: ...LUSTRATIONS Figure No Title Page 1 Field Strength Meter 120 E Front Cover Open iv 2 Block Diagram Field Strength Meter 4 3 Field Strength Meter Rear View Battery Compartment Open 14 4 Field Strength M...

Page 5: ...CAUUATIRS OSCILLATOR Figure 1 Field Strength Meter 120 E Front Cover Open iv www americanradiohistory com...

Page 6: ...when meter is not energized Provision for using recorder Headphones high impedance not supplied Shielded unbalanced loop Batteries five 1 1 2 volt two 67 1 2 volt Provision for external power supply B...

Page 7: ...ration A 10 000 to 25 000 ohm telephone headset is recommended as an aid in identifying signals under observation and may be used at the same time readings are being made Description The 120 E Field S...

Page 8: ...required Recording An unmarked pin jack located below the indicating meter is for connection to a DC recording amplifier Theory of Operation The Field Strength Meter circuit is shown in the schematic...

Page 9: ...www americanradiohistory com...

Page 10: ...progressively in the RF attenuator With this arrangement noise originating in the front end circuits has no effect on output meter indications except on the 100 V M position Even on this position its...

Page 11: ...ugh R 33 and R 35 the oscillator output is divided into two paths 1 An RF path through C 54 injecting the RF voltage into the loop circuit 2 A DC path to ground through R 26 R 27 and R 28 The rectifyi...

Page 12: ...ing details of the plug terminals are shown in the schematic Figure 6 An Amphenol No 91 MPF6L plug is required to make this connection To convert the meter from internal to external battery operation...

Page 13: ...the signals are peaked rotate the 120 E to get minimum meter indication NOTE Due to the high degree of selectivity of this instrument it will be found to tune sharply and careful attention should be g...

Page 14: ...effect is to compress the range of the output voltages being relatively larger for weak signals and smaller for strong signals Under this condition the rectified output voltage and meter indications a...

Page 15: ...apparent drifting of the calibrating oscillator output and more often a frequency shift This effect appears most evident at the higher frequencies and may best be checked by tuning in a signal at the...

Page 16: ...le a Normal Field Alignment 1 Tune in a signal at a frequency in the vicinity of 1500 kc and adjust for a convenient in dication on the panel meter 2 Adjust C 52 and receiver tuning until dial indicat...

Page 17: ...AIN for a convenient indication 3 Adjust core of R F transformer T 1 for maximum indication on panel meter 4 Adjust core of loop loading coil L 2 for maximum indication on panel meter 5 Set signal gen...

Page 18: ...instrument must be returned to the factory for readjustment For trouble shooting a rough check of the attenuator ratios can be made by tuning in a signal adjusting the GAIN control for a reading of 10...

Page 19: ...14 www americanradiohistory com...

Page 20: ...re J m H T 5 CL W H LU Q H Z O Z Q W a f OZ Z O O Q J U fn CO N N N J U U U 15 U J1 www americanradiohistory com...

Page 21: ...X 16 X www americanradiohistory com...

Page 22: ...d description of each item ordered Replacement parts which will be supplied against an order may not be exact duplicates of the original parts However only minor differences in the electrical or mecha...

Page 23: ...ppf 10 500V Erie NPO K C 12 Same as C 11 C 13 Same as C 11 C 14 CAPACITOR PLASTIC 0 1 pf 20 150V Gudeman 337Y104 C 15 CAPACITOR CERAMIC 01 pf 20 1000V Centralab DD 1032 C 16 CAPACITOR CERAMIC 01 pf GM...

Page 24: ...f 10 500V Erie N220K C 49 Same as C 16 C 50 CAPACITOR CERAMIC 001124 10 500V Erie GP3 331 C 51 CAPACITOR PAPER 01 f 20 o 600V Aerovox P 89M C 52 Same as C 1 C 53 CAPACITOR CERAMIC 20 f 10 500V Erie NP...

Page 25: ...4 L 6 Same as L 4 L 7 Same as L 4 L 8 Same as L 4 L 9 Not used L 10 Not used L 11 Not used L 12 COIL IF p o attenuator per Nems Clarke A 120 239 M 1 METER FIELD STRENGTH 200 a scale per Nems Clarke B...

Page 26: ...ON 270 R 10 1 2W Allen Bradley EB 2211 RESISTOR FIXED COMPOSITION 820 l 10 I 2W Allen Bradley EB 8211 RESISTOR VARIABLE COMPOSITION 2 5K 10 2W Allen Bradley JA1N048P252UA Not used RESISTOR FIXED COMPO...

Page 27: ...E SPDT HH Smith 511 S 5 SWITCH PLUNGER Micro V3 1 T 1 TRANSFORMER RF per Nems Clarke A 120 169 T 2 Not used T 3 TRANSFORMER IF Automatic Mfg Co 1655 8 T 4 Same as T 3 T 5 Same as T 3 T 6 COIL LOCAL OS...

Page 28: ...a 65 e2 I O 2 W9 S uR iH O 0 LI A 2 1 04 W y a So 0 t N K u aamll a ul A LLX o ol d o OI J z zay A 0J in 0 II nO a 4 4 Y a o le rcm rc rc 3 rc 4 000 NO o NY O CIO rc III Q Ol 1 000 000 a lY 2U1 S l 0...

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