HP-803A-Manual 电路图.pdf

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1、HP Archive This vintage Hewlett Packard document was preserved and distributed by www. h parch Please visit us on the web ! Thanks to on-line curator: Kenneth Kuhn for supplying and scanning this vintage document. RadioFans.CN 收音机爱 好者资料库 OPERATING AND SERVICING MANUAL .* T 0. 33A1.6.37-1 803A VHF BR

2、IDGE S E R I A L PRINTED 1-60 RadioFans.CN 收音机爱 好者资料库 CLAIM FOR DAMAGE IN SHIPMENT The instrument should be tested as soon as it is received. If it fails to operate properly, or is damaged in any way, a claim should be filed with the carrier. A full report of the damage should be obtained by the cla

3、im agent, and this report should be forwarded to us. We will then advise you of the disposition to be made of the equipment and arrange for repair or replacement. Include model number and serial number when referring to this instrument for any reason. W A R R A N T Y Hewlett-Packard Company warrants

4、 each instrument manufactured by them to be free from defects in material and workmanship. Our liability under this warranty is limited to servicing or adjusting any instrument returned to the factory for that purpose and to replace any defective parts thereof. Klystron tubes as well asjother electr

5、on tubes, fuses and batteries are specifically excluded from any liability. This warranty is effective for one year after delivery to the original purchaser when the instrument is returned, transportation charges prepaid by the original purchaser, and when upon our examination it is disclosed to our

6、 satisfaction to be defective. If the fault has been caused by misuse or abnormal conditions of operation, repairs will be billed at cost. In this case, an estimate will be submitted before the work is started. If any fault develops, the following steps should be taken: 1. Notify us, giving full det

7、ails of the difficulty, and include the model number and serial number. On receipt of this information, we will give you service data or shipping instructions. 2. On receipt of shipping instructions, forward the instrument prepaid, to the factory or to the authorized repair station indicated on the

8、instructions. If requested, an estimate of the charges will be made before the work begins provided the instru- ment is not covered by the warranty. S H I P P I N G All shipments of Hewlett-Packard instruments should be made via Truck or Railway Express. The instruments should be packed in a strong

9、exterior container and surrounded by two or three inches of excelsior or similar shock-absorbing material. DO NOT HESITATE TO CALL ON US PAL0 ALTO.CALlF. U.SA wW J 803A-16E Cable Assembly. iii CONTENTS GENERAL DESCRIPTION PAGE SECTION I1 SECTION 111 SECTION IV SECTlON V 1 - 1 General . 1 - 2 Damage

10、in Transit . 1 - 3 Auxiliary Equipment Required . . . . . . . . . . . . . . . 1 - 1 1 - 1 1 - 1 OPERATING INSTRUCTIONS 2 - 1 Controls and Terminals . . . . . . . . . . . . . . . . . . . 2 - 2 Dial Calibration . 2 - 3 Operating Procedure . 2 - 4 Phase Angle at Frequencies # 100 MC . . . . . . . . . .

11、 . 2 - 5 Multiple Nulls . 2 - 6 Operation wirh Radiating Loads . . . . . . . . . . . . . . . MEASUREMENT INTERPRETATION AND THE Z-THETA CHART 3 - 1 3 - 2 3 - 3 3 - 4 3 - 5 3 - 6 3 - 7 3 - 8 3 - 9 3 . 10 3 . 11 Direct Measurement . . . . . . . . . . . . . . . . . . . . . Remote Measurement. General .

12、 . . . . . . . . . . . . . . Z-Theta Charts. General . . . . . . . . . . . . . . . . . . Z-Theta Chart Description . . . . . . . . . . . . . . . . . Remote Measurement Procedure. Lossless Line Remote Measurement. Lossy Line . . . . . . . . . . . . . . Remote Measurement. Lines Other Than 50 ohms Cor

13、rection Charts . Limitation Remote Measurement . . . . . . . . . . . . . . VSWR Measurement . Measuring Balanced Impedances . . . . . . . . . . . . . . . . . . . . . . . . . THEORY AND MAINTENANCE I1 . 1 I1 . 1 I1 . 1 11 . 2 11 . 2 I1 . 2 111 . 1 111 . 1 111 . 1 111 . 1 111 . 2 111 . 4 I11 . 6 I11 .

14、 6 111 . 6 111 . 9 111 . 9 4 - 1 Theory o f Operation . IV . 1 4 - 2 Accuracy Check . 1V . 2 4 - 3 Maintenance General . IV . 2 4 - 4 Lubrication . IV . 2 TABLE OF REPLACEABLE PARTS 5 - 2 Table of Replaceable Parts . . . . . . . . . . . . . . . . . v - 2 iv Model 803A 1-1 GENERAL Sect. I Page 1 SECT

15、ION I GENERAL DESCRIPTION lined in the “Claim for Damage” section in this manual. The Model 803A VHq Bridge operates on the Byrne-bridge principle which separately couples 1-3 AUXILIARY EQUIPMENT REQUIRED to the E and M fields in a transmission line. Two attenuators are controlled simultaneouslv. on

16、e responds to the E field while the other responds TO operate the Model 803A a signal source of the to the M field. Both are adjusted for equal output. desired frequency must be connected to the GENER- The resulting signals are applied to opposite ends ATOR terminat, and a receiver which will respon

17、d of a slotted line section. Impedance phase angle to this frequency must be conected to the DE- is determined by the location of the cancellation TECTOR terminal. point in the slotted section as detected by a sliding RF GENERATOR. The signal generator driving probe. This bridge arrangement covers t

18、he frequency the bridge should have a power output of at least range from 50 MC to 500 MC and measures im- one milliwatt, and be capable of amplitude modu- pedance directly in the range from 2 to2000 ohms. lation. One of the Hewlett-Packard Model 608 Phase angle of the impedance is measureddirectly

19、VHF Signal Generators is recommended for this at 100 MC, but is readily computed at other application. frequencies. RF DETECTOR. The detector used with the bridge should be a receiver preferably with a sensitivGy at least 90 db below the signal-generator level. This detector must be thoroughly shiel

20、ded since any spurious signal of the test frequency picked up by the receiver in a manner other than the slotted section probe will result in an indeterminate balance and inaccurate results. The Hewlett-Pack- ard Model 417A VHF Detector was specifically designed for use with theModel803Aandis recom-

21、 mended for this application. 1-2 DAMAGE IN TRANSIT Should shipping damage be in evidence upon un- packing this instrument, follow the procedure out- Byme, J. F., “A Null-Method for Determination of Impedance in the 100-400 MC Range”, Proc. Natl Elec. Conf., Vol. 3, p. 603, 1947. Model 803A Sect. 11

22、 Page 1 SECTION II OPERATING INSTRUCTIONS CAUTION: THERE IS NO REASON FOR REMOVINGTHE REAR COVER OF THE INSTRUMENT. Experience has shown that many bridges are damaged by removing the rear cover, particularly if the PHASE dial is not set to 45 before removing the cover. GENERATOR signal to drive the

23、bridge. UNKNOWN known impedance to be measured. - This BNC jack accepts a source - This type N terminal accepts the un- SHORTING PLUG - This plug is used to check the accuracy of the instrument as described in paragraph 4-2. DETECTOR - This BNC jack accepts the detector connection. MAGNITUDE - This

24、control adjusts the position of the attenuators and drives the dial which gives the impedance magnitude at balance. PHASE - This control is ganged to the probe which moves in the slotted section around the bridge and drives the dial indicating impedance phase ,angle at balance. When the signal gener

25、ator is operating at the desired frequency, the receiver is tuned until a signal is heard. Should the bridge chance to be at balance, the signal may be difficult to detect, and it is advisable to move the PHASE and MAGNITUDE controls slightly to obtain a loud working signal. When the bridge is opera

26、ting correctly the signal at un- balance will be approximately 40 db below the level of the signal at the bridge input. When the working signal has been obtained the PHASE and MAGNITUDE controls are adjusted until a sharp null is obtained. When the knobs have been adjusted for an absolute null, the

27、impedance magnitude and phase angle may be read directly from the dials on the VHF Bridge. The nulls obtained by the bridge under the proper conditions of receiver sensitivity and signal level are extremely sharpat high frequencies and shallow at low frequencies and may be difficult to locate under

28、certain conditions. When the approximate value of the impedance is known, however, the null is detectable without difficulty. When the approximate value of the impedance under test is not known, the following procedure should be used. 1) Reduce either the signal level from the generator or reduce th

29、e sensitivity of the receiver until the signal is barely audible. When the Model 417A VHF Detector is employed, use the QUENCH control rather than the VOLUME control for this operation. 2) Adjust the PHASE and MAGNITUDE controls for a reduction in the signal level. The sequence of this adiustment is

30、 not important, and the controls 2-2 DIAL CALIBRATION The concentric indicating dials on the Model 803A read out impedance and phase angle. The upper dial indicates impedance directly in ohms inde- pendent of frequency. The lower dial indicates phase angle at 100 MC. The positive phase angle calibra

31、tions in black indicate an inductive reac- tance. The negative phase angle calibrations in red indicate a capacitive reactance. To obtain imped- ance phase angle at any frequency, see para. 2-4. 2-3 OPERATING PROCEDURE The recommended arrangement for conducting measurement tests with the Model 803Ai

32、s shownin Figure 2-1. may be-adjusted simultaneously. .With a low signal level or a low detector sensitivity, the region of the null is easily located. Sect. I1 Page 2 Model 803A MODEL 608 VHF SIGNAL GENERATOR MODEL 803A VHF BRIDGE MODEL 417A VHF DETECTOR POWER LINE Figure 2-1. Arrangement of Test E

33、quipment 3) When the null region has been established, in- crease the signal level or sensitivity of the re- ceiver and adjust the controls for further local- ization of the null. As the null is localized, continue to increase the signal level until the final null is obtained. 2-4 PHASE ANGLE AT FRE

34、QUENCIES #100MC The nature of the bridge permits the PHASE control to be calibrated at any single frequency. The im- pedance phase angle of any other frequency is de- fined by the ratio of the actual frequency to the calibrated frequency. To facilitate calculation, the PHASE dial on the Model 803A i

35、s calibrated for a frequency of 100 MC. The actual phase angle is determined by the expression: x (Dial reading e) signal frequency 100 MC e= 2-5 MULTIPLE NULLS At high frequencies it is possible to obtain several nulls on the phase dial. The significant null is the one which is closest to the zeroo

36、nthe PHASE dial. This condition exists because most impedance phase angles will fall between -90 and + 90 and as the frequency is increased, the corresponding dial range is decreased. For example, at 300 MC, a phase angle range from -90 to + 90 represents a dial range from -30 to +30. (See para. 2-4

37、.) 2-6 OPERATION WITH RADIATING LOADS In many cases measurement will be conducted for antenna impedance or other load impedances under conditions where appreciable radiated energy is present around the bridge and the detector. The Model 803A has been carefully checked for leakage, and the Model 417A

38、 VHF Detector has been designed with shielding for such applications. However, a very small amount of leakage into the detector will cause erroneous results. When a radiating load is located close to the bridge, a well-shielded cable must be used connecting the bridge to the detector. Ordinary RF do

39、uble braid shielded cable is in- adequate in some cases, and copper-clad cable should be used with both ends of the cable carefully grounded to the connectors. This precaution is normally adequate for satisfactory results with radiating loads. When the shielding is adequate, bridge balances will be

40、sharp and unaffected by touching or grounding various parts of the bridge circuit or cables. Inadequate shielding will reveal itself as inconsist- ent repeat results, and as a shifting null when the receiver or bridge is touched or grounded. Model 803A Sect. 111 Page 1 SECTION 111 MEASUREMENT INTERP

41、RETATION AND THE 2-THETA CHART J iiy) I 3-1 DIRECT MEASUREMENT The Model 803A measures load impedance at a point in the line, located by design considerations, 3 cm behind the UNKNOWN panel connector. Although this length has been made as short as possible circumstances arise in which the actual imp

42、edance is transformed by this length of line, and the 803A will not give the desired impedance directly. At high frequencies this condition may become quite pronounced even with the load con- nected directly across the bridge terminal. This length of line is equivalent to a series in- ductance of 0.

43、0059 ph and a shunt capacitance of 2.45 ppf when loads are connected directly across the bridge terminal, and the impedance reading may be corrected by the use of the equivalent circuits shown in Figure 3-1 or by the use of the Z - e chart, paragraph 3-5. 1 Z , : 2 to 2000n MODEL 803A 2.45)luF MODEL

44、 003A z (I (508 ) Figure 3-1. Equivalent Circuits for Internal Line Length 3-2 REMOTE MEASUREMENT, GENERAL In many cases it is desired to connect the imped- ance under test to the bridge through a length of transmission line. When this is done the load impedance is transformed by whatever line lengt

45、h is used and a correction must be applied to the reading of the bridge to give the actual impedance. The correction to be applied is found by the use of a Z-Theta chart described in paragraphs 3-3, through 3-8. 3-3 Z-THETA CHARTS, GENERAL Two transparent films of the Z-e chart will be found in the

46、back of this instruction manual. One chart has a center value of 50 ohms (Zo = 50 ohms) for direct use with 50 ohmsystems. The other chart is normalized with Zo = 1 for use in other systems. Dry process prints can be made from these transparencies for use with the 803A bridge. 3-4 Z-THETA CHART DESC

47、RIPTION The Z- chart is an impedance coordinate system used for the yphical solution of transmission line problems j 2 similar to the better known Smith Chart3 While the Smith Chart is based upon a rectangular coordinate system for imped- ance or admittance, the Z 0 chart is constructed kagan, G. L.

48、 et al; MICROWAVE TRANSMIS- SION CIRCUlTS Vol. 9, MIT RAD LAB), Section 2-12, McGraw-Hill, New York, 1948. %erman, F. E., Pettit, J. M., ELECTRONIC MEASUREMENTS, p. 157, McGraw-Hill, New York, 1952. 3Smith, P. H., “An Improved Transmission Line Calculator” “Electronics”, p. 130, January 1944. Sect. 111 Page 2 Model 803A as a polar coordinate system. Such a chart is shown in Figure 4 with a description of the ele- ments. For purposes of illustration, referring to Figure 3-3, assume that a 50