Agilent Technologies 382A Variable Attenuator Operating and Service Manual Agilent Part Number: 00382-90037 Printed in USA Print Date: July 2001 Supersedes: February 2001
Notice The information contained in this document is subject to change without notice. Agilent Technologies makes no warranty of any kind with regard to this material, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. Agilent Technologies shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this material.
What You’ll Find In This Manual… • • • • • Overview, page 1 Specifications, page 3 Operation, page 4 Maintenance, page 17 Replacement Parts List, page 27 Agilent 382A Operating And Service Manual iii
Warranty Custom systems are warranted by contractual agreement between Agilent Technologies and the customer. Certification Agilent Technologies, Inc., certifies that this product met its published specifications at the time of shipment from the factory.
Service and Support Any adjustment, maintenance, or repair of this product must be performed by qualified personnel. Contact your customer engineer through your local Agilent Technologies Service Center. You can find a list of local service representatives on the Web at: http://www.agilent.com/find/assist Click on “Contact Us” and select your country.
Safety and Regulatory Information Review this product and related documentation to familiarize yourself with safety markings and instructions before you operate the instrument. This product has been designed and tested in accordance with international standards. WARNING The WARNING notice denotes a hazard. It calls attention to a procedure, practice, or the like, that, if not correctly performed or adhered to, could result in personal injury.
1SM1-A This text indicates that the instrument is an Industrial Scientific and Medical Group 1 Class A product (CISPER 11, Clause 4). This symbol indicates that the power line switch is ON. This symbol indicates that the power line switch is OFF or in STANDBY position. This product complies with the WEEE Directive (2002/96/EC) marking requirements. The affixed label indicates that you must not discard this electrical/ electronic product in domestic household waste.
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Overview The Agilent Technologies 382A variable precision attenuators are designed for use in waveguide systems operating in the 3.95 to 40.0 GHz range. Each model of the 382A series provides calibrated attenuation from zero to 50 dB at any frequency within the rated waveguide band. Attenuation is read directly on the dial. Residual attenuation (at zero setting) is less than 1 dB over the waveguide range. Backlash is less than 0.3 dB at 50 dB.
Overview When the tension is released, the drive cable can jump out of the grooved portion of the drum, in which case the flag will be positioned approximately half way between the scales. If this should occur, the trouble is easily remedied: remove the cover and slip the cable back into its groove on the drum. The accuracy of the attenuator will not be affected in any way.
Specifications Specifications Table 1 Specifications Characteristic Frequency range (GHz) X382A P382A K382A R382A 8.2 to 12.4 12.4 to 18.0 18.0 to 26.5 26.5 to 40.0 Incremental attenuation range 1 0 to 50 dB Residual attenuation 2 Less than 1 dB Reflection coefficient Less than 0.07 (1.15 SWR), entire range of attenuation and frequency. Incremental attenuation accuracy Fits waveguide size ± 2% of the reading in dB, or 0.1 dB, whichever is greater.
Operation Operation Align Flanges The height of the 382A should be adjusted carefully so that precise alignment will be obtained at the coupling flanges to prevent undue strain on one flange while the other is unsupported. A screw at each corner of the base will enable height and leveling adjustments to be made. When the instrument is supported at both ends, as in permanent installations, the feet or base may be removed altogether, if desired (K or R bands). CAUTION Do not force dial stops.
Operation When all films are aligned, the E field of the applied field is normal to all films. When this occurs, no current flows in the films and no attenuation occurs. If the center film is rotated to some angle ? , the E field can be considered to be split into two orthogonal components: E sin ? in the plane of the film, and E cos ? at right angles to it.
Operation at all frequencies. Therefore, above cutoff of the TE 21 mode, in the top one-quarter of the frequency band, some sharp resonance could occur unless these modes are suppressed. Polyiron grooves are added in the center section to overcome these sources of error. Table 2 shows the test instruments and accessories required for performance checking. Test instruments other than those listed may be used provided their performance equals or exceeds the critical specifications.
Operation Specifications Determination Table 3 outlines the test procedure necessary to determine if the 382A meets specifications. Space is provided for recording the test results. Table 3 Test Card Agilent Model 382A Results Instrument Serial No. Test Performed By Date Description of Test Test Limits Standing Wave Ratio, SWR ?? 1.15 Residual Attenuation, ? 1.0 dB Attenuator Calibration: 10 dB ± (0.2 dB – mismatch error) 20 dB ± (0.4 dB – mismatch error) 30 dB ± (0.
Operation Standing Wave Ratio Figure 2 This test will obtain the SWR by measuring the reflection coefficient and calculating the SWR. Connect the instruments as shown in Figure 2. RF Pre-Insertion – Y-Z Recorder Setup for ? Tests Procedure for using this set-up consists of shorting the output (100% reflection) and then drawing a calibration grid of traces on the recorder around the expected value by varying the calibrating attenuator. For instance, if a reflection coefficient of 0.
Operation Set calibrating attenuator to zero and replace short with terminated attenuator to be tested. Trigger final sweep, which will be the SWR versus frequency characteristics of the attenuator under test. Since we wish to determine if the SWR is below 1.15, we can calibrate the reflectometer for this value and check that the attenuator under test stays below that value for all frequencies within its rated band. From a reflectometer calculator we obtain for SWR = 1.15 a return loss of 23.
Operation NOTE This procedure does not correct for other system errors 8. Repeat this measurement with the attenuator under test set to 10, 20, 30, 40, 50 dB and MAX attenuation. The SWR must remain less than 1.15 (25 dB return loss calibration line) throughout the frequency range of the attenuator under test. If any of these traces go through the calibration line the attenuator may or may not be out of specifications depending upon how the extra reflections in the system combine.
Operation Residual Attenuation Figure 3 This test measures the minimum loss introduced into a system by the use of the 382A variable attenuator under test. Using the setup of Figure 3 proceed as follows: Residual Attenuation Setup 1. Remove the test 382A from the setup and connect together. 2. With sweep oscillator set for single frequency operation at one end of the Model 382A band adjust variable attenuator to obtain SWR Meter reading of 3 dB on any convenient range.
Operation Moding Test The following test determines that the attenuator is functioning at all frequencies and not just at the test frequencies. If the attenuator does not attenuate at certain frequencies (moding) spikes will appear on the attenuation curve. To obtain this curve proceed as follows: 1. Connect instruments are show in Figure 4. 2. Set 382A under test to 50 dB. 3. Sweep a line for the entire frequency band of the 382A under test.
Operation 6. If excessive backlash is found, refer to Figure 5 and complete the rest of the procedure. If the backlash is within specifications the remainder of the adjustments in this paragraph need not be performed. 7. Check the position of the ring nut. It should be backed off approximately 1/4 turn from snug against the bearing. 8. Adjust the worm gear tension adjustment screw to minimize backlash. 9. Adjust the worm gear thrust adjustment screw to minimize backlash.
Operation Setting The Dial The dial will need resetting if a new dial is installed, if the stops have been forced hard, or if the dial has slipped. To reset the dial connect as in Figure 3 on page 11 and proceed as follows: 1. Set signal source to lowest point of 382A frequency range. Adjust the output RF signal for 1000 Hz square wave modulation. 2. Set 382A under test to dot which appears at approximately 47 dB on the attenuator dial.
Operation Attenuator Calibration Calibrate 10 dB System Error Since we are to calibrate the attenuator in 10 dB steps we must first calibrate the 10 dB attenuator on the SWR meter. To do this we substitute a calibrated directional coupler. Proceed as follows: Figure 6 Attenuator Calibration 1. Connect the instruments as shown in Figure 6. 2. Remove the 382A under test and reconnect the system (marked "CALIBRATE" in Figure 6). 3. Set variable attenuator to 41 dB. 4.
Operation 8. Read SWR meter and determine attenuation change from reference reading. Subtract the calibration value. The remainder (with the appropriate sign) is the true value of the SWR meter 10 dB range attenuation. Record this value and use it as the corrected reference point for all measurements at this frequency. Calibrate 382A The 382A can now be accurately calibrated since the error in the system is known. Proceed as follows: 1.
Maintenance Maintenance No maintenance is required on the K382A or the R382A. On other models, the only maintenance required is occasional lubrication of the bearing surfaces. The worm and worm gear, ball bearings, gears, flag shaft, and the ends of the center section (see Figure 5 on page 13) should be lubricated with a light grease such as Lubriplate #105V.* Replacing The Dial Resistive Card Replacement Procedure Align the "0" placement on dial with "Max".
Maintenance NOTE Center card passes thru the horizontal and meets a stop approximately 1/32 of an inch beyond this point (as measured at edge of card). 3. Note position of flag with respect to dial. The flag should be at the bottom of travel and the dial "0" (zero) should be to right of the center line. 4. Loosen clamping screws on flag drive cable. Free flag. 5. Drive locator pins to center of unit with punch. See Figure 7. Note: In some models the drive pin is an integral part of the casting.
Maintenance Figure 7 Agilent 382A Attenuator Assembly Detail Agilent 382A Operating and Service Manual 19
Maintenance Center Section Resistive Card Replacement 1. Remove flag cable from center section. Clean section. Drive locator pins from center section. Mark the position of the cable clamping device. 2. Remove ring nut (lock nut) and rubber "O" ring from center barrel. 3. Remove screws and separate halves. 4. Refer to Figure 8. Remove silver paint in card recess with acetone. This operation must be thorough. Any old paint left in recess may cause bowing of card.
Maintenance 5. Apply conductive silver paint (Acheson Industries, Electodag 5065S, Agilent Stock No. 9260-0910) along the edges of the center section halves as shown in Figure 9. Figure 9 Application of Conductive Silver Paint to Center Section 6. Install center card with emulsion side up (deposited side) in the recessed center section half as shown in Figure 10 page 22.
Maintenance NOTE To identify the emulsion side, scratch the extreme edge (that portion which will be covered by conductive paint). The emulsion side when scratched will become transparent. Figure 10 Installation of Resistive Card in Center Section 7. Replace drive pin in marked half of center section to act as guides. This is the half marked in step 7 under “To Dismantle” on page 17”. Replace top half of center section. Seat drive pins with pliers. 8.
Maintenance NOTE Do not remove pins; just loosen screws. Steps 5 through 12 must be completed before silver paint dries (approximately 1/2 hour). 13. Refer to Figure 11. Apply conductive silver to seams of choke joint on ends of center section. Figure 11 NOTE Application of Silver Paint to Choke Joint of Center Section Paint these ends well. Failure to do so will cause excessive insertion loss. 14. Replace "O" ring and ring nut. Small OD should be outboard on ring nut.
Maintenance 2. Drive locator pins from end section (see Figure 12). Figure 12 Installation of Resistive Card in End Section 3. Remove screws and separate halves. 4. Refer to Figure 13. Remove silver paint from both halves with acetone. Figure 13 Removal of Silver Paint from End Section 5. Apply conductive silver paint along the inner edges of the end section halves as shown in Figure 14.
Maintenance Figure 14 Application of Conductive Silver Paint o End Section 6. Install end card with emulsion (deposited) side up in recessed half of the end section as shown in Figure 12. 7. Replace top half. Seat drive pins with pliers. 8. Install screws with heads up. 9. Check card for wrinkles. If necessary, remove wrinkles as described in step 12 under “Center Section Resistive Card Replacement” on page 20. 10. Install choke and/or bearing ring. Make sure parts are properly seated.
Maintenance 7. Check backlash by applying inward pressure on the knob end of the shaft. The shaft should move freely and spring back to its original position. 8. Attach flag cable. 9. Lubricate worm gear (recommended lubricant: Mobilux No. 1, Mfg. by Mobil Oil Co., or Moly Grease, Agilent Stock No. 6040-0012). Dial Cord Replacement 1. With dial set to 50, run cable through lug on center section and clamping screw. 2. Position flag behind 50 and tighten clamp screw.
Replacement Parts List Replacement Parts List This section contains replaceable parts for the 382A. Table 4 lists replaceable parts in alphanumerical order of their reference designators. Miscellaneous parts are included at the end of the list. Detailed information includes the following. • • • • • • • Table 4 Reference designator. Full description of the part. Manufacturer of the part in a single-digit code; see list of manufacturers, as follows. Agilent Technologies part number.
Replacement Parts List Reference Item Description Frequency Bands Mfr.1 Agilent Part No.
Replacement Parts List Code List of Manufactures Code No. Manufacturer Address 1 Cole Rubber and Plastics Inc. Sunnyvale, Calif. 2 Fafnir Bearing Co., The New Britain, Conn. 3 Agilent Technologies Palo Alto, Calif.
Replacement Parts List 30 Agilent 382A Operating and Service Manual
