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1. The narrowest usable bandwidth in turn is limited by the tracking generator residual FM and any tracking drift between the analyzer tuning and the tracking generator signal Introduction to Spectrum Analysis F 02m f 20853190 pas ryoyenaaty Ju apolt saduy peut x 9 dnudungy 04114 mur A DapIA oroso e907 PE THINS 6C BEATIE ed3eId YO L 314 Imenso pappojpio7 1962 i i2 Ex aleyon ionun 403114 eg on marmury uwes one LTL Te 04H 0 mo Pug apnd THINS 609 39314 sseg pueg ULPwwrDS owun ntes Sunny THSNOSES ost 1010128 moo 154 JIGUAY sop m 12003 1911409 21 APPENDIX dBm CONVERSION The most common measurement of RF signal levels is in Some users measure signal level in dBmV where 0 dB dBm where 0 dBm equals 1 milliwatt across 50 ohms 224 equals 1 millivolt in dBuV where 0 dB equals 1 micro mV The Models 2615A 2620A 2625 and 2630 read volt or directly in millivolts or microvolts The following signal level in dBm table provides conversion from dB to other measurement schemes dBm Conversion Chart dBm dBmV dByV uV mV dBm dBmV dBHV uV mV dBm dBmV dByV uV mV 13 60 120 1000 mV 26 21 81 11 2 mV 64 17 43 141 HV 12 59 4119 891 mV 27 20 80 10 0 mV 65 18 42 126 HV 14 58 4118 794 mV 28 19 79 8 91 mV 66 19 41 112 uV 10 57 117 707 mV 29 18 78 7 94 mV 67 20 40 100 p2. switch is engaged the noise level decreases and the selectivity is improved Spectral lines which are relatively close together can be distinguished As the small signal transient response requires a longer time this causes incorrect amplitude values if the scanwidth is set at too wide a frequency span The UNCAL LED will indicate this condition 11 VIDEO FILTER The video filter may be used to reduce noise on the screen It enables small level spectral lines to become visible which normally would be within or just above the medium noise level The filter bandwidth is 4 kHz 12 Y POS Control for adjusting the vertical beam position 13 INPUT The BNC 500 input of the spectrum analyzer Without input attenuation the maximum permissible input voltages of 25V DC and 10 dBm AC must not be exceeded With the maximum input attenuation of 40 dB the maximum input voltage is 20 dBm The maximum dynamic range of the instrument is 70 dB Higher input voltages exceeding the reference level cause signal compression and intermodulation Those effects will lead to erroneous displays If the input level exceeds the reference level the input level attenuation must be increased 14 ATTN ATTENUATOR The Input Attenuator consists of four 10 dB attenuators reducing the signal height before entering the 1st mixer Each attenuator is active if the push button is depressed The correlation of selected attenuation reference level and baseline le
3. when the input signal is equal to the internal noise level the signal will appear 3 dB above the noise When the signal power is added to the average noise power the power level on the CRT is doubled increased by 3 dB because the signal power average noise power The maximum input level to the spectrum analyzer is the damage level or burn out level of the input circuit This is 10 dBm for the input mixer and 20 dBm for the input attenuator Before reaching the damage level of the analyzer the analyzer will begin to gain compress the input signal This gain compression is not considered serious until it reaches 1 dB The maximum input signal level which will always result in less than 1 dB gain compression is called the linear input level Above 1 dB gain compression the analyzer is considered to be operating nonlinearly because the signal amplitude displayed on the CRT is not an accurate measure of the input signal level Whenever a signal is applied to the input of the analyzer distortions are produced within the analyzer itself Most of these are caused by the non linear behavior of the input mixer These distortions are typically 70 dB below the input signal level for signal levels not exceeding 27 dBm at the input of the first mixer To accommodate larger input signal levels an attenuator is placed in the input circuit before the first mixer The largest input signal that can be applied at each setting of the input attenuator w
4. and the power level at each frequency is displayed The frequency domain is a graphical representation of signal amplitude as a function of frequency The frequency domain contains information not found in the time domain and therefore the spectrum analyzer has certain advantages compared with an oscilloscope The analyzer is more sensitive to low level distortion than a scope Sine waves may look good in the time domain but in the frequency domain harmonic distortion can be seen The sensitivity and wide dynamic range of the spectrum analyzer is useful for measuring low level modulation It can be used to measure AM FM and pulsed RF The analyzer can be used to measure carrier frequency modulation frequency modulation level and modulation distortion Frequency conversion devices can be easily characterized Such parameters as conversion loss isolation and distortion are readily determined from the display The spectrum analyzer can be used to measure long and short term stability Parameters such as noise sidebands on an oscillator residual FM of a source and frequency drift during warm up can be measured using the spectrum analyzers calibrated scans 17 The swept frequency responses of a filter or amplifier are examples of swept frequency measurements possible with a spectrum analyzer These measurements are simplified by using a tracking generator Types of Spectrum Analyzers There are two basic types of spectrum analyzer
5. generator itself In conjunction with the spectrum analyzer the tracking generator produces a signal whose frequency precisely tracks the spectrum analyzer tuning The tracking generator frequency precisely tracks the spectrum analyzer tuning since both are effectively tuned by the same VTO This precision tracking exists in all analyzer scan modes Thus in full scan the tracking generator output is a start stop sweep in zero scan the output is simply a CW signal 20 The tracking generator signal is generated by synthesizing and mixing two oscillators One oscillator is part of the tracking generator itself the other oscillator is the spectrum analyzer lst LO The spectrum analyzer tracking generator system is used in two configurations open loop and closed loop In the open loop configuration unknown external signals are connected to the spectrum analyzer input and the tracking generator output is connected to a counter This configuration is used for making selective and sensitive precise measurement of frequency by tuning to the signal and switching to zero scan In the closed loop configuration the tracking generator signal is fed into the device under test and the output of the device under test is connected to the analyzer input In this configuration the spectrum analyzer tracking generator becomes a self contained complete source detector and display swept frequency measurement system An internal leveling loop in
6. line corresponds to 0 Hz With these settings a spectral line is visible which is referred to as Zero Frequency It is the Ist LO oscillator which becomes visible when its frequency passes the first IF filter This occurs when the center frequency is low relative to the scanwidth range selected The Zero Frequency is different in level in every instrument and therefore cannot be used as a reference level Spectral lines displayed left of the Zero Frequency Point are so called image frequencies In the ZERO SCAN mode the spectrum analyzer operates like a receiver with selectable bandwidth The frequency is selected via the CENTER FREQ knob Spectral line s passing the IF filter cause a level display selective voltmeter function The selected scanwidth div settings are indicated by a number of LEDs above the range setting push buttons SCANWIDTH Models 2615A and 2620A The SCANWIDTH selectors allow to control the scanwidth per division of the horizontal axis The frequency Div can he increased by means of the button and de creased by means of the lt button Switching is accomplished in 1 2 5 steps from 50 KHz div to 50 MHz div The width of the scan range is displayed in MHz div and refers to each horizontal division on the graticule 13 CONTROLS AND INDICATORS The center frequency is indicated by the vertical graticule line at middle of the horizontal axis If the center frequency and the scanwidth sett
7. mV 55 8 452 398 UV 93 46 14 5 01 HV 17 30 90 31 6 mV 56 9 451 355 HV 94 47 13 4 47 uV 18 29 89 28 2 mV 57 10 50 316 HV 95 48 12 3 98 HV 19 28 88 25 1 mV 58 11 49 282 uV 96 49 11 3 55 HV 20 27 87 22 4 mV 59 12 48 251 HV 97 50 10 3 16 HV 21 26 86 20 0 mV 60 13 47 224 UV 98 51 9 2 82 UV 22 25 85 17 8 mV 61 14 46 200yV 99 52 8 2 51 HV 23 24 84 15 8 mV 62 15 45 178 HV 100 53 7 2 24 uV 24 23 83 14 1 mV 63 16 44 158 pV 25 22 82 12 6 mV 22 CUSTOMER SUPPORT 1 800 462 9832 B K Precision offers courteous professional technical support before and after the sale of their test instruments The following services are typical of those available from our toll free telephone number Technical advice on the use of your instrument e Information on instrument repair and recalibration services Technical advice on special applications of your instru ment e Replacement parts ordering Technical advice on selecting the best instrument for a e Information on other B K Precision instruments given task e Requests for a new B4K Precision catalog Information on optional accessories for your instrument e The name of your nearest B K Precision distributor Call toll free 1 800 462 9832 Monday through Thursday 8 00 A M to 5 00 P M Friday 8 00 A M to 12 00 P M Pacific Standard Time Pacific Daylight Time in summer INSTRUMENT REPAIR SERVICE Because of the special
8. to 50 MHz If the 50 MHz spectral line is not on the second graticule line from left it should be aligned using the X AMPL control 17 Then the calibration as described under C should be verified and corrected if necessary The calibrations C and D should be repeated until optimum adjustment is achieved Horizontal Calibration Models 2615A and 2620A Prior to calibration ensure that all input attenuators switches 14 are released The spectrum analyzer must be operated for at least 60 minutes prior to calibration The VIDEO FILTER push button 11 must be in OFF position CALIBRATION Set BANDWIDTH 10 to 250 kHz Set the SCANWIDTH 15 to 50 MHz div After the center frequency is set to 250 MHZ a generator signal must be applied to the input The output level should be between 40 and 50 dB above the noise C Set generator frequency to 250 MHz Adjust the peak of the 250 MHz spectral line to the horizontal screen center using the X POS control 16 16 D Set the generator frequency to 50 MHz If the 50 MHz spectral line is not on the 2nd graticule line from left it should be aligned using the X AMPL control 17 Then the calibration as described under C should be verified and corrected if necessary The calibrations C and D should be repeated until optimum adjustment is achieved Introduction to Spectrum Analysis General The analysis of electrical signals is a fundamental problem for many engineers and sci
9. type of spectrum analyzer differs from the trf spectrum analyzers in that the spectrum is swept through a fixed bandpass filter instead of sweeping the filter through the spectrum The analyzer is basical a narrowband receiver which is electronically tuned in frequency by applying a saw tooth voltage to the frequency control element of a voltage tuned local oscillator This same saw tooth voltage is simultaneously applied to the horizontal deflection plates of the CRT The output from the receiver is synchronously applied to the vertical deflection plates of the CRT and a plot of amplitude versus frequency is displayed The analyzer is tuned through its frequency range by varying the voltage on the LO local oscillator Introduction to Spectrum Analysis The LO frequency is mixed with the input signal to produce an IF intermediate frequency which can be detected and displayed When the frequency difference between the input signal and the LO frequency is equal to the IF frequency then there is a response on the analyzer The advantages of the superheterodyne technique are considerable It obtains high sensitivity through the use of IF amplifiers and many decades in frequency can be tuned Also the resolution can be varied by changing the bandwidth of the IF filters However the superheterodyne analyzer is not real time and sweep rates must be consistent with the IF filter time constant A peak at the left edge of the CRT is sometime
10. 0 1 to 500 MHz for Model 2620A The tracking generator frequency is determined by the first oscillator 1st LO of the spectrum analyzer section Spectrum analyzer and tracking generator are frequency synchronized Operating Considerations It is very important to read Safety in the GENERAL INFORMATION Section including the instructions prior to operating the spectrum analyzer No special knowledge is necessary for the operation of the spectrum analyzer The straightforward front panel layout and the limitation to basic functions guarantee efficient operation immediately To ensure optimum operation of the instrument some basic instructions need to be followed CAUTION The most sensitive component of the spectrum analyzer is the input section It consists of the signal attenuator and the first mixer Without input attenuation the vollage at the input must not exceed 10 dBm 0 7Vrms AC or 25 volt DC With a maximum input attenuation of 40 dB the AC voltage must not exceed 20 dBm Exceeding these limits will damage the input attenuator and or the first mixer Prior to examining unidentified signals the presence of unacceptable high voltages has to be checked It is also recommended to start measurements with the highest possible attenuation and a maximum frequency range The user should also consider the possibility of excessively high signal amplitudes outside the covered frequency range although not displayed e g 1200 MH
11. Qo Cc LLI N gt lt 2 lt gt Cc H O Lu A Qo MANUAL INSTRUCTION TEST INSTRUMENT SAFETY Normal use of test equipment exposes you to a certain amount of danger from electrical shock because testing must sometimes be performed where exposed voltage is present An electrical shock causing 10 milliamps of current to pass through the heart will stop most human heartbeats Voltage as low as 35 volts dc or ac rms should be considered dangerous and hazardous since it can produce a lethal current under certain conditions Higher voltages pose an even greater threat because such voltage can more easily produce a lethal current Your normal work habits should include all accepted practices to prevent contact with exposed high voltage and to steer current away from your heart in case of accidental contact with a high voltage You will significantly reduce the risk factor if you know and observe the following safety precautions 1 Don t expose high voltage needlessly Remove housings and covers only when necessary Turn off equipment while making test connections in high voltage circuits Discharge high voltage capacitors after removing power 2 If possible familiarize yourself with the equipment being tested and the location of its high voltage points However remember that high voltage may appear at unexpected points in defective equipment 3 Use an insulated floor material or a large insulated
12. RT 6 inch 8 x 10 div internal graticule Trace rotation Adjustable on front panel Output Probe Power 6V Line voltage 115 230V 10 50 60Hz Power consumption approx 27W Operating ambient temperature 10 C to 40 C Protective system Safety Class I IEC 1010 1 Weight Approx 15 4 Ib 6 kg Models 2625 and 2630 Approx 13 2 Ib 5 kg Models 2615A and 2620A Dimensions 4 9 in 125 mm H x 11 2 in 285mm W x 15 in 380 mm D Accessories Supplied Power Cord Instruction Manual NOTE Specifications and information are subject to change without notice Please visit www bkprecision com for the most current product information OPTIONAL ACCESSORIES Near Field Sniffer Probe Set Model PR 261 The PR 261 is the ideal tool kit for the investigation of RF electromagnetic fields It is indispensable for EMI pre compliance testing during product development prior to third party testing The set includes three hand held probes with a built in pre amplifier covering the frequency range from 10 kHz to 1000 MHz The set includes one magnetic field probe one electric field probe and one high impedance probe All have high sensitivity and are matched to the XD inputs of spectrum analyzers The power can be supplied either from the batteries or through a power cord directly connected to a B K Precision Models 2615A 2620A 2625 and 2630 Signal feed is via a 1 5 meter BNC cable When used in conjunc tion with a spectrum
13. T BNC connector at a frequency determined by the spectrum analyzer In ZERO SCAN mode the center frequency appears at the output 24 LEVEL This knob adjusts the level of the tracking generator Continuously variable from 10 dBm to 1 dBm operates in conjunction with step attenuators for 1 dBm to 50 dBm output level CALIBRATION Vertical Calibration Models 2625 and 2630 Prior to calibration ensure that all input attenuators 14 are released The spectrum analyzer must be in operation for at least 60 minutes prior to calibration Switch VIDEO FILTER 11 to OFF position Set BANDWIDTH 10 to 400 kHz Set SCANWIDTH 15 to 2 MHz div Connect calibrated RF signal of 27 dBm 0 2 dB 10 mV to the spectrum analyzer input 13 The frequency of this signal should be between 2 MHz and 250 MHz Set the center frequency to the signal frequency A A single spectral line 27 dBm appears on the screen The spectral line maximum is now adjusted with the Y POS control 12 and placed at the top graticule line of the screen All input attenuators switches have to be released The following adjustment is only necessary for service purposes and if the check of this settings shows deviations of the correct settings The y ampl control is located on the XY PCB inside the instrument In case any adjustment of the vertical amplification is necessary please refer to the service manual B Next the generator signal must be switche
14. V 9 56 116 631 mV 30 17 77 7079 pV 68 21 39 89 1 HV 8 55 4115 562 mV 31 16 76 6310 uV 69 22 38 79 4 HV 7 54 114 501 mV 32 15 75 5623 uV 70 23 37 70 7 HV 6 53 4113 447 mV 33 14 74 5012 uV 71 24 36 63 1 HV 5 452 4112 398 mV 34 13 73 4467 uV 72 25 35 56 2 HV 4 51 111 355 mV 35 12 72 3981 uV 73 26 34 50 1 HV 3 50 110 316 mV 36 14 71 3548 uV 74 27 33 44 7 uV 2 49 109 282 mV 37 10 70 3162 uV 75 28 32 39 8 HV 1 48 4108 251 mV 38 9 69 2818 uV 76 29 31 35 5 HV 0 47 107 224 mV 39 8 68 2512 uV 77 30 30 31 6 HV 1 46 106 200 mV 40 7 67 2239 UV 78 31 29 28 2 uV 2 45 105 178 mV 41 6 66 1995 uV 79 32 28 25 1 HV 3 44 104 158 mV 42 5 65 1778 uV 80 33 27 22 4 uV 4 43 103 141 mV 43 4 64 1585 pV 81 34 26 20 0 pV 5 42 102 126 mV 44 3 63 1413 uV 82 35 25 17 8 HV 6 41 101 112 mV 45 2 62 1259 uV 83 36 24 15 8 HV 7 40 100 100 mV 46 1 61 1122 uV 84 37 23 14 1 uV 8 39 99 89 1 mV 47 0 60 1000 pV 85 38 22 12 6 HV 9 38 98 79 4 mV 48 1 59 891 uV 86 39 21 11 2 HV 10 37 97 70 7 mV 49 2 58 794yV 87 40 20 10 0 pV 11 36 96 63 1 mV 50 3 57 707 HV 88 41 19 8 91 HV 12 35 95 56 2 mV 51 4 56 6314V 89 42 418 7 94 uV 13 34 94 50 1 mV 52 5 55 562 MV 90 43 17 7 07 uV 14 33 93 44 7 mV 53 6 54 501 pV 91 44 16 6 31 HV 15 32 92 39 8 mV 54 7 53 447 uV 92 45 15 5 62 HV 16 31 91 35 5
15. actory in a safe condition This instruction manual contains important information and warn ings which have to be followed by the user to ensure safe operation and to retain the Spectrum Analyzer in a safe condition Fig 1 Tilt Handle Operation The case chassis and all measuring terminals are connected to the protective earth contact of the appliance inlet The instrument operates according to Safety Class I three conductor power cord with protective earthing conductor and a plug with earthing contact The mains line plug shall only be inserted in a socket outlet provided with a protective earth contact The protective action must not be negated by the use of an extension cord without a protective conductor The mains line plug should be inserted before connections are made to measuring circuits The grounded accessible metal parts case sockets jacks and the mains line supply contacts line live neutral of the instrument have been tested against insulation breakdown with 2200V DC Under certain conditions 50 Hz or 60 Hz hum voltages can occur in the measuring circuit due to the interconnection with other mains line powered equipment or instruments This can be avoided by using an isolation transformer Safety Class II between the mains line outlet and the power plug of the device being investigated Most cathode ray tubes develop X rays However the dose equivalent rate falls far below the maximum permissible value of 36pA k
16. analyzer the probes can be used to locate and qualify EMI sources They are especially suited to locate emission hot spots on PCBs and cables as well as evaluate EMC problems at the breadboard and prototype level They enable the user to evaluate radiated fields and perform shield effectivity comparisons Mechanical screening performance and immunity tests on cables and components are easily performed Faulty components and poor bonding locations can be isolated The magnetic probe incorporates a high degree of rejection of both stray and direct electric fields and provides far greater repeatability than with conventional field probes Measurements can be made on the very near field area that is close to components or radiation sources The electric field monopole probe has the highest sensitivity of all three probes It can be used to check screening and perform pre compliance testing on a comparative basis The high impedance probe is used to measure directly on the components under test or at the conductive trace of a PC board It has an input capacitance of only 2 pF and supplies virtually no electrical charge to the device under test Probe Set Specifications All probes are electrically shielded and are supplied in a carrying case Frequency range 100 kHz 1 2GHz Power supply 6V from Spectrum Analyzers or Batteries Operating current 10 15 mA Probe dimensions 40 x 19 x 195 mm approx Antenna Kit Model AN 18 Broad
17. ave to be released B Next the generator signal must be switched back and forth between 27 dBm and 77 dBm and the Y AMPL control adjusted so that the spectral line peak changes by 5 divisions in the vertical direction If this results in a change of the Y position the calibration outlined under A has to be repeated The calibrations A and B have to be repeated until an ideal adjustment is achieved Finally the operation of the input attenuators 14 can be tested at a level of 27 dBm The spectral line visible on the screen can be reduced in 4 steps of 10 dB each by activating the attenuators incorporated in the spectrum analyzer Each 10 dB step corresponds to one graticule division on the screen The tolerance may not exceed l dB in all attenuation positions Horizontal Calibration Models 2625 and 2630 Prior to calibration ensure that all input attenuators switches 14 are released The spectrum analyzer must be operated for at least 60 minutes prior to calibration The VIDEO FILTER push button 11 must be in OFF position Set BANDWIDTH 10 to 400 KHz Set the SCANWIDTH 15 to 50 MHz div After the center frequency is set to 250 MHz a generator signal must be applied to the input The output level should be between 40 and 50 dB above the noise C Set generator frequency to 250 MHz Adjust the peak of the 250 MHz spectral line to the horizontal screen center using the X POS control 16 D Set the generator frequency
18. band antenna is useful for radiated signal measurement Deluxe Carrying Case Model LC 210 Rugged cordura carrying case is foam padded for instrument protection has zipped pockets for manual and accessories and includes web hand strap and shoulder strap 50 ohm to 75 ohm Matching Network Model ZTF 1 Most RF networks except cable TV have an impedance of 50 ohms The spectrum analyzers also have a 50 ohm input impedance which allows direct connection Cable TV networks have an impedance of 75 ohms To use the spectrum analyzer with 75 ohm networks Model ZTF 1 will match the 75 ohm network to the 50 ohm input impedance of the spectrum analyzer 50 ohm Feedthru Termination Model TE 26 The output levels of the tracking generator of the Models 2620 and 2630 are correct only when terminated into 50 ohms The Model TE 26 provides a 50 ohm termination and a BNC feedthru connection so that the tracking generator output may be fed into high impedance circuit at a calibrated level GENERAL INFORMATION The Models 2615A 2620A 2625 and 2630 spectrum ana lyzers are easy to operate The logical arrangement of the controls allows anyone to quickly become familiar with the operation of the instrument however experienced users are also advised to read through these instructions so that all functions are understood Immediately after unpacking the instrument should be checked for mechanical damage and loose parts in the interior If th
19. ceiver principle The signal to be measured fin 0 5 MHz to 500 MHz is applied to the 1st mixer where it is mixed with the signal of a variable voltage controlled oscillator f 610 MHz 1110 MHz This oscillator is called the 1st LO local oscillator The difference between the oscillator and the input frequency fio fin 1st IF is the first intermediate frequency which passes through a waveband filter tuned to a center frequency of 609 5 MHz It then enters an amplifier and this is followed by two additional mixing stages oscillators and amplifiers The second IF is 29 5 MHz and the third is 2 9 MHz In the third IF stage the signal can be selectively transferred through a filter with 250 KHz or 20 kHz bandwidth before arriving at an AM demodulator The logarithmic output video signal is transferred directly or via a low pass filter to another amplifier This amplifier output is connected to the Y deflection plates of the CRT The X deflection is performed with a ramp generator voltage This voltage can also be superimposed on a dc voltage which allows for the control of 1st LO The spectrum analyzer scans a frequency range depending on the ramp height This span is determined by the scanwidth setting In ZERO SCAN mode only the direct voltage controls the 1st LO Models 2620A and 2630 each include a tracking generator This generator provides sine wave voltages within the frequency range of 0 1 to 1050 MHz for Model 2630 and
20. d back and forth between 27 dBm and 77 dBm and the Y AMPL control adjusted so that the spectral line peak changes by 5 divisions in the vertical direction If this results in a change of the Y position the calibration outlined under has to be repeated The calibrations A and B have to be repeated until an ideal adjustment is achieved Finally the operation of the input attenuators 14 can be tested at a level of 27 dBm The spectral line visible on the screen can be reduced in 4 steps of 10 dB each by activating the attenuators incorporated in the spectrum analyzer Each 10 dB step corresponds to one graticule division on the screen The tolerance may not exceed 1 dB in all attenuation positions Vertical Calibration Models 2615A and 2620A Prior to calibration ensure that all input attenuators 14 are released The spectrum analyzer must be in operation for at least 60 minutes prior to calibration Switch VIDEO FILTER 11 to OFF position Set BANDWIDTH 10 to 250 kHz Set SCANWIDTH 15 to 2 MHz div Connect calibrated RF signal of 27 dBm 0 2 dB 10 mV to the spectrum analyzer input 13 The frequency of this signal should be between 2 MHz and 250 MHz Set the center frequency to the signal frequency 15 A A single spectral line 27 dBm appears on the screen The spectral line maximum is now adjusted with the Y POS control 12 and placed at the top graticule line of the screen All input attenuators switches h
21. e input Also refer to INPUT 12 15 15 This permits the detection of any spectral lines which are within the maximum measurable and displayable frequency range if the center frequency is set to 500 MHz for Models 2625 and 2630 or 250 MHz for Models 2615A and 2620A If the baseline tends to move upwards when the attenuation is decreased it may indicate spectral lines outside the maximum displayable frequency range with excessive amplitude SCANWIDTH Models 2625 and 2630 The SCANWIDTH selectors allow to control the scanwidth per division of the horizontal axis The frequency Div can be increased by means of the button and decreased by means of the lt button Switching is accomplished in 1 2 5 steps from 100 kHz div to 100 MHz div The width of the scan range is displayed in MHz div and refers to each horizontal division on the graticule The center frequency is indicated by the vertical graticule line at middle of the horizontal axis If the center frequency and the scanwidth setting are correct the X axis has a length of 10 divisions On scanwidth settings lower than 100 MHz only a part of the entire frequency range is displayed When SCANWIDTH is set to 100 MHz div and if center frequency is set to 500 MHz the displayed frequency range extends to the right by 100 MHz per division ending at 1000 MHz 500 MHz 5 x 100 MHz The frequency decreases to the left in a similar way In this case the left graticule
22. elative frequency measurements require a linear frequency scan By measuring the relative separation of two signals on the display the frequency difference can be determined 18 It is important that the spectrum analyzer be more stable than the signals being measured The stability of the analyzer depends on the frequency stability of its local oscillators Stability is usually characterized as either short term or long term Residual FM is a measure of the short term stability which is usually specified in Hz peak to peak Short term stability is also characterized by noise sidebands which are a measure of the analyzers spectral purity Noise sidebands are specified in terms of dB down and Hz away from a carrier in a specific bandwidth Long term stability is characterized by the frequency drift of the analyzers LOs Frequency drift is a measure of how much the frequency changes during a specified time i e Hz min or Hz hr Resolution Before the frequency of a signal can be measured on a spectrum analyzer it must first be resolved Resolving a signal means distinguishing it from its nearest neighbors The resolution of a spectrum analyzer is determined by its IF bandwidth The IF bandwidth is usually the 3 dB bandwidth of the IF filter The ratio of the 60 dB bandwidth in Hz to the 3 dB bandwidth in Hz is known as the shape factor of the filter The smaller the shape factor the greater is the analyzers capability to resolve close
23. ensitivity specifications for equal bandwidths A spectrum analyzer sweeps over a wide frequency range but is really a narrow band instrument All of the signals that appear in the frequency range of the analyzer are converted to a single IF frequency which must pass through an IF filter the detector sees only this noise at any time Therefore the noise displayed on the analyzer is only that which is contained in the IF passband When measuring discrete signals maximum sensitivity is obtained by using the narrowest IF bandwidth Video Filtering Measuring small signals can be difficult when they are ap proximately the same amplitude as the average internal noise level of the analyzer To facilitate the measurement it is best to use video filtering A video filter is a post detection low pass filter which averages the internal noise of the analyzer When the noise is averaged the input signal may be seen If the resolution bandwidth is very narrow for the span the video filter should not be selected as this will not allow the amplitude of the analyzed signals to reach full amplitude due to its video bandwidth limiting property 19 Introduction to Spectrum Analysis Spectrum Analyzer Sensitivity Specifying sensitivity on a spectrum analyzer is somewhat arbitrary One way of specifying sensitivity is to define it as the signal level when signal power average noise power The analyzer always measures signal plus noise Therefore
24. entists Even if the immediate problem is not electrical the basic parameters of interest are often changed into electrical signals by means of transducers The rewards for transforming physical parameters to electrical signals are great as many instruments are available for the analysis of electrical signals in the time and frequency domains The traditional way of observing electrical signals is to view them in the time domain using an oscilloscope The time domain is used to recover relative timing and phase informa tion which is needed to characterize electric circuit behavior However not all circuits can be uniquely characterized from just time domain information Circuit elements such as amplifiers oscillators mixers modulators detectors and filters are best characterized by their frequency response information This frequency information is best obtained by viewing electrical signals in the frequency domain To display the frequency domain requires a device that can discriminate between frequencies while measuring the power level at each One instrument which displays the frequency domain is the spectrum analyzer It graphically displays voltage or power as a function of frequency on a CRT cathode ray tube In the time domain all frequency components of a signal are seen summed together In the frequency domain complex signals i e signals composed of more than one frequency are separated into their frequency components
25. ere is transport damage the supplier must be informed immediately The instrument must then not be put into operation Symbols FAN ATTENTION refer to manual Danger High voltage Protective ground earth terminal Tilt handle To view the screen from the best angle there are three different positions C D E for setting up the instrument see Figure 1 If the instrument is set down on the floor after being carried the handle automatically remains in the upright carrying position A In order to place the instrument onto a horizontal surface the handle should be turned to the upper side of the Spectrum Analyzer C For the D position 10 inclination the handle should he turned to the opposite direction of the carrying position until it locks in place automatically underneath the instrument For the E position 20 inclination the handle should be pulled to release it from the D position and swing backwards until it locks once more The handle may also be set to a position for horizontal carrying by turning it to the upper side to lock in the B position At the same time the instrument must be lifted because otherwise the handle will jump back Safety This instrument has been designed and tested in accordance with ZEC Publication 1010 1 Safety requirements for elec trical equipment for measurement control and laboratory use The CENELEC regulations EN 61010 1 correspond to this standard It has left the f
26. floor mat to stand on and an insulated work surface on which to place equipment and make certain such surfaces are not damp or wet 4 Use the time proven one hand in the pocket technique while handling an instrument probe Be particularly careful to avoid contacting a nearby metal object that could provide a good ground return path 5 When testing ac powered equipment remember that ac line voltage is usually present on some power input circuits such as the on off switch fuses power transformer etc any time the equipment is connected to an ac outlet even if the equipment is turned off 6 Some equipment with a two wire ac power cord including some with polarized power plugs is the hot chassis type This includes most recent television receivers and audio equipment A plastic or wooden cabinet insulates the chassis to protect the customer When the cabinet is removed for servicing a serious shock hazard exists if the chassis is touched Not only does this present a dangerous shock hazard but damage to test instruments or the equipment under test may result from connecting the ground lead of most test instruments to a hot chassis To test hot chassis equipment always connect an isolation transformer between the ac outlet and the equipment under test The B K Precision Model TR 110 Isolation Transformer or Model 1653A or 1655A AC Power Supply is suitable for most applications To be on the safe side treat all two w
27. g 0 5mR h Whenever it is likely that protection has been impaired the instrument shall be made inoperative and be secured against any unintended operation The protection is likely to be impaired if for example e shows visible damage e fails to perform the intended measurements GENERAL INFORMATION e has been subjected to prolonged storage under unfavorable conditions e g in the open or in moist environments e has been subjected to severe transport stress e g in poor packaging Operating Conditions The instrument has been designed for indoor use The permissible ambient temperature range during operation is 10 C 450 F to 40 C 104 F It may occasionally be subjected to temperatures between 10 C 50 F and 10 C 14 F without degrading its safety The permissible ambient temperature range for storage or transportation is 40 C 14 F to 70 C 158 F The maximum operating altitude is up to 2200m The maximum relative humidity is up to 80 If condensed water exists in the instrument it should be acclimatized before switching on In some cases e g instrument extremely cold two hours should be allowed before the instrument is put into operation The instrument should be kept in a clean and dry room and must not be operated in explosive corrosive dusty or moist environments The spectrum analyzer can be operated in any position but the convection cooling must not be impaired For cont
28. hen is sensitivity To ensure a maximum dynamic range on the CRT display check to see that the following requirements are satisfied 1 The largest input signal does not exceed the optimum input level of the analyzer typically 27 dBm with 0 dB input attenuation 2 The peak of the largest input signal rests at the top of the CRT display reference level Frequency Response The frequency response of an analyzer is the amplitude linearity of the analyzer over its frequency range If a spectrum analyzer is to display equal amplitudes for input signals of equal amplitude independent of frequency then the conversion power loss of the input mixer must not depend on frequency If the voltage from the LO is too large compared to the input signal voltage then the conversion loss of the input mixer is frequency dependent and the frequency response of the system is nonlinear For accurate amplitude measurements a spectrum analyzer should be as flat as possible over its frequency range Flatness is usually the limiting factor in amplitude accuracy since it s extremely difficult to calibrate out And since the primary function of the spectrum analyzer is to compare signal levels at different frequencies a lack of flatness can seriously limit its usefulness Tracking Generators The tracking generator Models 2620A and 2630 only is a special signal source whose RF output frequency tracks follows some other signal beyond the tracking
29. hile maintaining the internally generated distortions below a certain level is called the optimum input level of the analyzer The signal is attenuated before the first mixer because the input to the mixer must not exceed 27 dBm or the analyzer distortion products may exceed the specified 70 dB range This 70 dB distortion free range is called the spurious free dynamic range of the analyzer The display dynamic range is defined as the ratio of the largest signal to the smallest signal that can be displayed simultaneously with no analyzer distortions present Dynamic range requires several things then The display range must be adequate no spurious or unidentified response can occur and the sensitivity must be sufficient to eliminate noise from the displayed amplitude range The maximum dynamic range for a spectrum analyzer can be easily determined from its specifications First check the distortion spec For example this might be all spurious products 70 dB down for 27 dBm at the input mixer Then determine that adequate sensitivity exists For example 70 dB down from 27 dBm is 97 dB This is the level we must be able to detect and the bandwidth required for this sensitivity must not be too narrow or it will be useless Last the display range must be adequate Introduction to Spectrum Analysis Notice that the spurious free measurement range can be extended by reducing the level at the input mixer The only limitation t
30. ing are correct the X axis has a length of 10 divisions On scanwidth settings lower than 50 MHz only a part of the entire frequency range is displayed When SCANWIDTH is set to 50 MHz div and if center frequency is set to 250 MHz the displayed frequency range extends to the right by 50 MHz per division ending at 500 MHz 250 MHz 5 x 50 MH2 The frequency decreases to the left in a similar way In this case the left graticule line corresponds to 0 Hz With these settings a spectral line is visible which is referred to as Zero Frequency It is the Ist LO oscillator which becomes visible when its frequency passes the first IF filter This occurs when the center frequency is low relative to the scanwidth range selected The Zero Frequency is different in level in every instrument and therefore cannot be used as a reference level Spectral lines displayed left of the Zero Frequency Point are so called image frequencies In the ZERO SCAN mode the spectrum analyzer operates like a receiver with selectable bandwidth The frequency is selected via the CENTER FREQ knob Spectral line s passing the IF filter cause a level display selective voltmeter function The selected scanwidth div settings are indicated by a number of LEDs above the range setting push buttons 16 X POS X position 17 X AMPL X amplitude IMPORTANT These controls are only necessary when calibrating the instrument They do not require adju
31. inuous operation the instrument should be used in the horizontal position preferably tilted upwards resting on the tilt handle The specifications stating tolerances are only valid if the instrument has warmed up for 60 minutes at an ambient temperature between 15 C 59 F and 30 C 86 F Values without tolerances are typical for an average instrument Maintenance Various important properties of the spectrum analyzer should be carefully checked at certain intervals Only in this way it is certain that all signals are displayed with the accuracy on which the technical data are based The exterior of the instrument should be cleaned regularly with a dusting brush Dirt which is difficult to remove on the casing and handle the plastic and aluminum parts can be removed with a moistened cloth 99 water 1 mild detergent Spirit or washing benzene petroleum ether can be used to remove greasy dirt The screen may be cleaned with water or washing benzene but not with spirit alcohol or solvents it must then be wiped with a dry clean lint free cloth Under no circumstances may the cleaning fluid get into the instrument The use of other cleaning agents can attack the plastic and paint surfaces Selecting the Line Voltage The spectrum analyzer operates at mains line voltages of 115V AC and 230V AC The voltage selection switch is located on the rear of the instrument and displays the selected voltage The correct voltage ca
32. ire ac equipment as hot chassis unless you are sure it has an isolated chassis or an earth ground chassis 7 On test instruments or any equipment with a 3 wire ac power plug use only a 3 wire outlet This is a safety feature to keep the housing or other exposed elements at earth ground 8 B K Precision products are not authorized for use in any application involving direct contact between our product and the human body or for use as a critical component in a life support device or system Here direct contact refers to any connection from or to our equipment via any cabling or switching means A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause failure of that device or system or to affect its safety or effectiveness 9 Never work alone Someone should be nearby to render aid if necessary Training in CPR cardio pulmonary resuscitation first aid is highly recommended Instruction Manual for BK PRECISION Models 2615A 2620A 2625 2630 SPECTRUM ANALYZERS BK PRECISION TABLE OF CONTENTS Page Page TEST INSTRUMENT SAFETY Inside front cover INTRODUCTION TO SPECTRUM ANALYSIS 17 SPECIFICATIONS eeeeeeeeeeee esee ee tenta nnns enn 5 General 5 aped bou RR ERR 17 OPTIONAL ACCESSORIES ee eeee ee eene 6 Types of Spectrum Analyzers sss 17 GENERAL INFORMATION ee 7 Spectrum Anal
33. ized skills and test equipment required for instrument repair and calibration many customers prefer to rely upon B K PRECISION for this service We maintain a network of B K PRECISION authorized service agencies for this purpose To use this service even if the instrument is no longer under warranty follow the instructions given in the WARRANTY SERVICE INSTRUCTIONS portion of this manual There is a nominal charge for instruments out of warranty 23 BK CISION Service Information Warranty Service Please go the support and service section on our website www bkprecision com to obtain a RMA Return the product in the original packaging with proof of purchase to the address below Clearly state on the RMA the performance problem and return any leads probes connectors and accessories that you are using with the device Non Warranty Service Please go the support and service section on our website www bkprecision com to obtain a RMA Return the product in the original packaging to the address below Clearly state on the RMA the performance problem and return any leads probes connectors and accessories that you are using with the device Customers not on an open account must include payment in the form of a money order or credit card For the most current repair charges please refer to the service and support section on our website Return all merchandise to B amp K Precision Corp with pre paid shipping The flat rate repair charge fo
34. ly spaced signals of unequal amplitude If the shape factor of a filter is 15 1 then two signals whose amplitudes differ by 60 dB must differ in frequency by 7 5 times the IF bandwidth before they can be distinguished separately Otherwise they will appear as one signal on the spectrum analyzer display The ability of a spectrum analyzer to resolve closely spaced signals of unequal amplitude is not a function of the IF filter shape factor only Noise sidebands can also reduce the resolution They appear above the skirt of the IF filter and reduce the offband rejection of the filter This limits the resolution when measuring signals of unequal amplitude The resolution of the spectrum analyzer is limited by its narrowest IF bandwidth For example if the narrowest bandwidth is 10 KHz then the nearest any two signals can be and still be resolved is 10 kHz This is because the analyzer traces out its own IF band pass shape as it sweeps through a CW signal Since the resolution of the analyzer is limited by bandwidth it seems that by reducing the IF bandwidth infinitely infinite resolution will be achieved The fallacy here is that the usable IF bandwidth is limited by the stability residual FM of the analyzer If the internal frequency deviation of the analyzer is 10 kHz then the narrowest bandwidth that can be used to distinguish a single input signal is 10 KHz Any narrower IF filter will result in more than one response or an intermittent
35. n be selected using a small screwdriver Remove the power cable from the power connector prior to making any changes to the voltage setting The fuses must also be replaced with the appropriate value see Fuse Type prior to connecting the power cable Both fuses are externally accessible by removing the fuse cover located above the 3 pole power connector The fuseholder can be released by pressing its plastic retainers with the aid of a small screwdriver see Figure 2 The retainers are located on the right and left side of the holder and must be pressed towards the center The fuse s can then be replaced and pressed in until locked on both sides Use of patched fuses or short circuiting of the fuseholder is not permissible B K Precision assumes no liability whatsoever for any damage caused as a result and all warranty claims become null and void Fuse type Size 5 x 20 mm 250 Volt AC must meet IEC specification 127 Sheet III or DIN 41 662 or DIN 41 571 sheet 3 Time characteristic time lag T 315mA T 160mA Line voltage 115V 10 Line voltage 230V 10 Fuse rating Fuse rating Fig 2 Fuse Replacement INTRODUCTION General The spectrum analyzer permits the detection of spectrum components of electrical signals in the frequency range of 0 15 to 1050 MHz for Models 2625 and 2630 and 0 15 to 500 MHz for Models 2615 and 2620 The detected signal and its content have to be repetitive In contrast to a
36. n oscilloscope operated in Yt mode where the amplitude is displayed on the time domain the spectrum analyzer displays amplitude on the frequency domain Yf The individual spectrum components of a signal become visible on a spectrum analyzer The oscilloscope would display the same signal as one resulting waveform Models 2625 and 2630 The spectrum analyzer works according to the triple superhet receiver principle The signal to be measured fin 0 15 MHz to 1050 MHZ is applied to the 1st mixer where it is mixed with the signal of a variable voltage controlled oscillator fto 1350 MHz 2350 MHz This oscillator is called the Ist LO local oscillator The difference between the oscillator and the input frequency fio fin 1st IF is the first intermediate frequency which passes through a waveband filter tuned to a center fre quency of 1350 MHz It then enters an amplifier and this is followed by two additional mixing stages oscillators and amplifiers The second IF is 29 875 MHz and the third is 2 75 MHz In the third IF stage the signal can be selectively transferred through a filter with 400 KHz or 20 kHz bandwidth before arriving at an AM demodulator The logarithmic output video signal is transferred directly or via a low pass filter to another amplifier This amplifier output is connected to the Y deflection plates of the CRT Models 2615A and 2620A The spectrum analyzer works according to the triple superhet re
37. ng from loss of use Some states do not allow limitations of incidental or consequential damages So the above limitation or exclusion may not apply to you This warranty gives you specific rights and you may have other rights which vary from state to state B amp K Precision Corp 22820 Savi Ranch Parkway Yorba Linda CA 92887 www bkprecision com 714 921 9095 25 NOTES 26 27 BK PRECISION 22820 Savi Ranch Parkway Yorba Linda CA 92887 v110409 Printed in China 28
38. quency When the switch is in the ON position MK is lit and the display shows the marker frequency The marker is shown on the screen as a sharp peak The marker frequency is adjustable by means of the MARKER knob and can be aligned with a spectral line NOTE Switch off the marker before taking correct amplitude readings CF MK CENTER FREQUENCY MARKER indicator The CF LED is lit when the digital display shows the center frequency The center frequency is the frequency which is displayed in the horizontal center of the CRT The MK LED is lit when the Marker pushbutton is in the ON position The digital display shows the marker frequency in that case DIGITAL DISPLAY Display of Center Frequency Marker Frequency 7 segment display with 100 kHz resolution UNCAL Blinking of this LED indicates incorrectly displayed amplitude values This is due to scanwidth and filter setting combinations which give uncalibrated amplitude readings because the IF filters have not settled This may occur when the scanned frequency range SCANWIDTH is too large compared to the IF bandwidth and or the video filter bandwidth Measurements in this case can either be taken without a video filter or the scanwidth has to be decreased 10 9 CENTER FREQUENCY Coarse Fine Both rotary knobs are used for center frequency setting The center frequency is displayed at the horizontal center of the screen 10 BANDWIDTH Selects the IF bandwidth When the
39. r Non Warranty Service does not include return shipping Return shipping to locations in North America is included for Warranty Service For overnight shipments and non North American shipping fees please contact B amp K Precision Corp B amp K Precision Corp 22820 Savi Ranch Parkway Yorba Linda CA 92887 www bkprecision com 714 921 9095 Include with the returned instrument your complete return shipping address contact name phone number and description of problem 24 LIMITED ONE YEAR WARRANTY B amp K Precision Corp warrants to the original purchaser that its products and the component parts thereof will be free from defects in workmanship and materials for a period of one year from date of purchase B amp K Precision Corp will without charge repair or replace at its option defective product or component parts Returned product must be accompanied by proof of the purchase date in the form of a sales receipt To obtain warranty coverage in the U S A this product must be registered by completing a warranty registration form on our website www bkprecision com within fifteen 15 days of purchase Exclusions This warranty does not apply in the event of misuse or abuse of the product or as a result of unauthorized alterations or repairs The warranty is void if the serial number is altered defaced or removed B amp K Precision Corp shall not be liable for any consequential damages including without limitation damages resulti
40. response for a single input frequency A practical limitation exists on the IF bandwidth as well since narrow filters have long time constants and would require excessive scan time Sensitivity Sensitivity is a measure of the analyzers ability to detect small signals The maximum sensitivity of an analyzer is limited by its internally generated noise This noise is basi cally of two types thermal or Johnson and nonthermal noise Thermal noise power can be expressed as PN kxTxB where PN Noise power in watts k Boltzmann s Constant 1 38x107 Joule K T absolute temperature K B bandwidth of system in Hertz As seen from this equation the noise level is directly proportional to bandwidth Therefore a decade decrease in bandwidth results in a 10 dB decrease in noise level and consequently 10 dB better sensitivity Nonthermal noise accounts for all noise produced within the analyzer that is not temperature dependent Spurious emissions due to nonlinearities of active elements impedance mismatch etc are sources of nonthermal noise A figure of merit or noise figure is usually assigned to this nonthermal noise which when added to the thermal noise gives the total noise of the analyzer system This system noise which is measured on the CRT determines the maximum sensitivity of the spectrum analyzer Because noise level changes with bandwidth it is important when comparing the sensitivity of two analyzers to compare s
41. s swept tuned and real time analyzers The swept tuned analyzers are tuned by electrically sweeping them over their frequency range Therefore the frequency components of a spectrum are sampled sequentially in time This enables periodic and random signals to be displayed but makes it impossible to display transient responses Real time analyzers on the other hand simultaneously display the amplitude of all signals in the frequency range of the analyzer hence the name real time This preserves the time dependency between signals which permits phase information to be displayed Real time analyzers are capable of displaying transient responses as well as periodic and random signals The swept tuned analyzers are usually of the trf tuned radio frequency or superheterodyne type A trf analyzer consists of a bandpass filter whose center frequency is tunable over a desired frequency range a detector to produce vertical deflection on a CRT and a horizontal scan generator used to synchronize the tuned frequency to the CRT horizontal de flection It is a simple inexpensive analyzer with wide frequency coverage but lacks resolution and sensitivity Because trf analyzers have a swept filter they are limited in sweep width depending on the frequency range usually one decade or less The resolution is determined by the filter bandwidth and since tunable filters do not usually have constant bandwidth is dependent on frequency The most common
42. s called the zero frequency indicator or local oscillator feedthrough It occurs when the analyzer is tuned to zero frequency and the local oscillator passes directly through IF creating a peak on the CRT even when no input signal is present For zero frequency tuning FLO FIF This effectively limits the lower tuning limit Spectrum Analyzer Requirements To accurately display the frequency and amplitude of a signal on a spectrum analyzer the analyzer itself must be properly calibrated A spectrum analyzer properly designed for accurate frequency and amplitude measurements has to satisfy many requirements Wide tuning range Wide frequency display range Stability Resolution Flat frequency response High sensitivity Low internal distortion OA EY c Frequency Measurements The frequency scale can be scanned in three different modes full per division and zero scan The full scan mode is used to locate signals because the widest frequency ranges are displayed in this mode Not all spectrum analyzers offer this mode The per division mode is used to zoom in on a particular signal In per division the center frequency of the display is set by the Tuning control and the scale factor is set by the Frequency Span or Scan Width control In the zero scan mode the analyzer acts as a fixed tuned receiver with selectable bandwidths Absolute frequency measurements are usually made from the spectrum analyzer tuning dial R
43. steps and 0 Hz div Zero Scan Frequency scanwidth accuracy 10 Frequency stability Drift 150 kHz hour IF Bandwidth 3 dB Resolution 400 kHz and 20 kHz Models 2625 and 2630 Resolution 250 kHz and 20 kHz Models 2615A and 2620A Video Filter on 4 kHz Sweep rate 43 Hz Amplitude Amplitude range 100 dBm to 13 dBm Screen display range 80 dB 10 dB div Reference level 27 dBm to 13 dBm in 10 dB steps Reference level accuracy 2 dB Average noise level 99 dBm 20 kHz BW Models 2625 and 2630 99 dBm 20 kHz BW Models 2615A and 2620A Distortion 15 dBc 2nd and 3rd harmonic 3rd order intermod 70 dBc two signals gt 3 MHz apart Sensitivity dB above average noise level Log scale fidelity 2 dB without attn Ref 250 MHz IF gain 10 dB adjustment range Input Input impedance 50 Input connector BNC Input attenuator 0 to 40 dB 4 x 10 dB steps Input attenuator accuracy 1 dB 10 dB step Max input level 10 dBm 25VDC 0 dB attenuation 20 dBm 40 dB attenuation Tracking Generator Models 2620A and 2630 only Output level range 50 dBm to 1 dBm in 10 dB steps and variable Output attenuator 0 to 40 dB 4 x 10 dB steps Output attenuator accuracy 1 dB Output impedance 50Q BNC Frequency range 0 15 MHz to 1050 MHz Model 2630 0 1 MHz to 500 MHz Model 2620A Frequency response 1 5 dB Radio Frequency Interference RFI lt 20 dBc General Display C
44. stment under normal operating conditions A very accurate RF Generator is necessary if any adjustment of these controls is required 18 PHONE 3 5 mm earphone connector An earphone or loudspeaker with an impedance gt 16 Ohms can be connected to this output When tuning the spectrum analyzer to a spectral line possibly available audio signals can be detected The signal is provided by an AM Demodulator in the IF section It demodulates any available AM Signal and provides as well one side FM Demodulation The output is short circuit proof 19 VOLUME Volume setting for earphone output 20 PROBE POWER The output provides a 5 Vdc voltage for the operation of an PR 261 near field sniffer probe It is only provided for this purpose and requires a special cable which is shipped along with the PR 261 probe set CONTROLS AND INDICATORS TRACKING GENERATOR CONTROLS Models 2620A and 2630 21 ATTN ATTENUATOR Output level attenuator with four 10 dB attenuators which allow the signal to be reduced prior to reaching the OUTPUT jack The four attenuators are equal and each is activated by depressing the button When engaged each provides a 10 dB attenuation Any combination of buttons may be used to achieve the desired attenuation 22 0UTPUT 50 BNC output of the tracking generator 14 23 TRACK GEN The tracking generator is activated when this button is engaged When activated a sine signal can be obtained at the OUTPU
45. the tracking generator ensures a leveled output over the entire frequency range The specific swept measurements that can be made with this system are frequency response amplitude vs frequency magnitude only reflection coefficient and return loss From return loss or reflection coefficient the SWR can be calculated Swept phase and group delay measurements cannot be made with this system however it does make some unique contributions not made by other swept systems such as a sweeper network analyzer a sweeper spectrum analyzer or a sweeper detector oscilloscope Precision tracking means at every instant of time the generator fundamental frequency is in the center of the analyzer passband and all generator harmonics whether they are generated in the analyzer or are produced in the tracking generator itself are outside the analyzer passband Thus only the tracking generator fundamental frequency is displayed on the analyzers CRT Second and third order harmonics and intermodulation products are clearly out of the analyzer tuning and therefore they are not seen Thus while these distortion products may exist in the measurement set up they are completely eliminated from the CRT display The 1 dB gain compression level is a point of convenience but it is nonetheless considered the upper limit of the dynamic range The lower limit on the other hand is dictated by the analyzer sensitivity which as we know is bandwidth dependent
46. vel noise level is according to the following listing Attenuation Reference level Base line 0 dB 27 dBm 10 mV 107 dBm 10 dB 17 dBm 31 6 mV 97 dBm 20 dB dBm 0 1 V 87 dBm 30 dB 3 dBm 316 mV 77 dBm 40 dB 13 dBm 1V 07 dBm CONTROLS AND INDICATORS RR TCR E s 2 Fw CENTER FREQ BENE SEERE ove 1 FS RE SE Ld dd bible e 500 MHz SPECTRUM ANALYZER Fig 4 Model 2620A Front Panel The reference level is represented by the upper As previously pointed out the maximum permissible input horizontal graticule line The lowest horizontal voltages may not be exceeded This is extremely important graticule line indicates the baseline The vertical because it is possible that the spectrum analyzer will only graticule is subdivided in 10 dB steps show a partial spectrum of currently applied signals 11 CONTROLS AND INDICATORS e z 2 e x BBBH BHHH 1000 Mix SPECTRUM ANALYZER ig 8 Ba cr Q Ps LJ t i p e riw a he 4 p MARKER CENTER FREG 5 8 on e eo Fig 6 Model 2630 Front Panel Consequently input signals might be applied The highest attenuation 4 x 10 dB and the highest with excessive levels outside the displayed usable frequency range highest scanwidth setting frequency range leading to the destruction of should be selected prior to connecting any signal to the the input attenuator and or the 1st mixing stag
47. yzer Requirements 18 SYMBOL Sr RE seed 7 Eibduiues Mee E nta s tat 18 Tilt handle rir eee eres 7 Safety nc REPRE 7 18 Operating Conditions pp 8 SenDSIti VIty ioi pete pmo er oe n 19 Maintenance danerne hee rte ee Ta IE E 8 SEES il sine RE dos Freue roms 19 Selecting the Line Voltage pp 8 Spectrum Analyzer Sensitivity pp 19 INTRODUCTION eeeeeee esee eene eet nnn nennen 9 pH UE ru e I 20 EL 9 Operating E CE MERIT T 9 Tracking Generators pt 20 APPENDIX dBm CONVERSION eee 22 CONTROLS AND INDICATORS 10 CUSTOMER SUPPORT eeeeeeeeee enne 23 CALIBRATION eeeeeeeeeeeee eese triones s esent nun 15 Vertical Calibration s seen 15 INSTRUMENT REPAIR SERVICE 28 Horizontal Calibration RN 15 WARRANTY SERVICE INSTRUCTIONS 24 LIMITED ONE YEAR WARRANTY 25 SPECIFICATIONS Frequency Frequency range 0 15 MHz to 1050 MHz 3 dB Models 2625 and 2630 0 15 MHz to 500 MHz 3 dB Models 2615A and 2620A Center frequency display accuracy 100 kHz Marker accuracy 0 1 span 100 kHz Frequency display resolution 100 kHz 4 digit LED for Models 2625 and 2630 4 digit LED for Models 2615A and 2620A Frequency scanwidth 100 kHz div to 100 MHz div Models 2625 and 2630 in 1 2 5 steps and 0 Hz div Zero Scan 50 kHz div to 50 MHz div Models 2615A and 2620A in 1 2 5
48. z The frequency range of 0 Hz to 150 kHz is not specified Spectral lines within this range would be displayed with incorrect amplitude A particularly high intensity setting shall be avoided The way signals are displayed on the spectrum analyzer typically allows for any signal to be recognized easily even with low intensity Due to the frequency conversion principle a spectral line is visible at O Hz It is called IF feedthrough The line appears when the Ist LO frequency passes the IF amplifiers and filters The level of this spectral line is different in each instrument A deviation from the full screen does not indicate a malfunctioning instrument CONTROLS AND INDICATORS The front panel controls of the instruments are shown in Figures 3 through 6 and are explained below 1 2 3 FOCUS Beam sharpness adjustment INTENS Beam intensity adjustment POWER Power ON and OFF If power is switched to ON position a beam will be visible on the screen after approximately 10 sec TR Trace Rotation Despite Mumetal shielding of the CRT effects of the earth s magnetic field on the horizontal trace position cannot be completely avoided A potentiometer accessible through an opening can be used for correction Slight pincushion distortion is unavoidable and cannot be corrected MARKER ON OFF switch When the MARKER pushbutton is set to the OFF position the CF indicator is lit and the display shows the center fre
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