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1. 15 MSK Mudulated DoLowTles ee FTP Setting Spheic Channel Synoptic Cleanup r Data Rate and Filtering r Select A D Card k j Primary Fiter Number A D Card Number NONE y Secondary Filter 2 Sample Feeney NONE A D Channel Number E Set Acquisition Timing C Narrowband Timina Number Den HH MM SS HH MM SS Previous Next Delete Stat 0 o o fo o fo Use this channel s timing for all chanrels End o 0 0 o 0 Sample Walk Through of a Simple Acquisition This tutorial will walk through the steps necessary for the following BROADBAND Setup 2 continuous broadband channels acquiring from 3 30 to 3 00 23 5 hours of the day We want the continuous broadband files to be split into 30 minutes segments e The broadband data will be filtered with a cutoff of 12500Hz The broadband data will be sampled at 100kHz NARROWBAND Setup 2 synoptic narrowband channels acquiring data the first 5 minutes of each day stuns at 0 00 and ending at 12 05 The narrowband data will be filtered with cutoff of 200Hz The narrowband data will be from the NLK transmitter mixed down from 24800 Hz The narrowband will be sampled at 50Hz The narrowband data amplitude will be scaled by a calibration factor of 5 e We will run the synoptic cleanup batch file for the narrowband data
2. In order to calibrate you need to know the antenna properties and the output corresponding to a known test signal at the input the calibration signal Using these parameters you can convert any voltage at the output to a magnetic field The calibration signal is generated at the very front end of the preamp card and is described elsewhere To activate the calibration mode enable the Aux1 jumper in the line receiver This will ensure that a one second long calibration pulse is injected every 32 seconds When the Aux1 jumper is removed at the end of testing the calibration tone will be disabled Since capturing the output of this calibration gives the antenna s response all that is required is to take several recordings that include a calibration pulse One minute recordings using the software would suffice Calibration will require the use of a dummy loop dummy loop replicates the Impedance of the intended antenna and enables signals to be injected at the input of the system The dummy loop s design and functions is described elsewhere Throughout the characterization process the dummy loop or an antenna should be connected to the preamplifier s input because system s response patticularly at low frequencies can be properly estimated only when the VLF input is loaded with the same impedance as it would with an antenna The process of calibration in the field requires executing a series of test recordings and observations o
3. Broadband files are named according to the following convention XXYYMMDDHHMMSS_ACC mat XX Station ID from Station Information Dialogue Box YY Year MM Month DD Day HH Hour Minute SS Second A zero based index of the ADC card that was used CC zeto based index of the software channel number that was used Station Information Station name Stanford Station ID sr Cancel Contact Edward Kim Address ctrl enter for new line Phone number 951 4401537 Email edward kim stantor Last Machg 2008 Installaion date March 8 005 ___ URL ar stanford du vif Stanford Test Site Description HARDWARE INFORMATION This is where the user can enter the hardware setup of this station Note that the user can enter multiple Preamp serial numbers by simply clicking on the add button and then using next and prev to navigate ADC Card can simply be the model name of the ADC card Again the fields in this GUI do not directly affect the data acquisition They are for informative purposes only The only exception is the pull down menu in which the user may select the type of GPS sytem Motorola or TrueTime that the system is hooked upto Hardware Information Del ANTENNA SETTINGS The user can enter various information about the antenna setup by clicking on the Antenna Settings button The fields in thi
4. vii Cabling Pin Connections Box Mount 14 Pin Connector Viewed from inside box A 15 Red Pair Light Wire B Cal Black Pair Light Wire C Cal Shield Black Pair Shield D Cal Black Pair Dark Wire E E W Orange Pair Light Wire F E W Orange Pair Datk Wire PC Mount 12 Pin Power Header Viewed from above G N S Yellow Pair Dark Wire H N S Shield Yellow Pair Shield I N S Yellow Pair Light Wire J 15V Red Pair Dark Wire K Gnd Red Pair Shield L No Connection M E W Shield Orange Pair Shield N No Connection Sa Box Mount Antenna Conn Viewed from inside box A Antenna B Common C Antenna D No Connection Mount 4 Pin Power Header Viewed from above Calibration Circuit The 2005 receiver includes a calibration circuit so that the frequency response of the system can be measured at any given time The calibration circuit block diagram is shown in figure 6 FPGA Control Line Output Cable to 8 192 MHz Driver Preamp Oscilattor PIC Antenna Processor Input Nodes Figure 6 Calibration Circuit Block Diagram The FPGA controls the calibration circuit typically turning it on for one second every five minutes however there are multiple modes selectable with the AuxA and AuxB jumpers The output driver sends a 15V signal across to the preamp activating an 8 192 MHz processor and a PIC processor The PIC processor generat
5. e The narrowband data will be FTPed to vlf europe stanford edu at 23 30 1 Setup the necessary hardware a Install a 200kHz NIDAQ ADC card in the PCI slot of the computer b Install the NIDAQ software and properly assign the ADC card to be device number 1 using the NIDAQ software Contact Eddie Kim for a copy of the NIDAQ software c Attach the line receiver to the ADC card d Attach the GPS receiver to the ADC card Contact Morris Cohen for instructions on how to do steps c and d 2 On the computer install the software package 3 Make sure SPYSWEEPER and NORTON ANTIVIRUS scheduled scans are disabled 4 Run the VLF DAQ console only exe This allows the user to change settings or the software without fear of data being acquired while settings are being changed 5 Enter the password in the password box Stanford University VLF DAQ Lee _ riestore settings 6 Click on Station Information and enter as much information as you can about the site copy of all this data is saved in the settings file which is important to consult when studying your acquired data Station Information EN ar stanford du 97y Stanford Test 7 Click OK on the Station Information Dialogue Box 8 Click on Hardware information and enter as much information as you can about the hardware setup of the site Hardware Information a Click on ADC Settings
6. reamplifier Backplane Ref Value Description Supplier Part G25 10 uF Tantalum Capacitor Digikey C26 0 1 uF Ceramic Capacitor Digikey D1 1N4005 Diode Digikey D2 LED Red LED Digikey MV3750 D3 LED Red LED Digikey MV3750 D4 LED Red LED Digikey MV3750 D5 LED Red LED Digikey MV3750 JA 12 Pin Power Header Digikey WM1629 J2 44 Pin 0 156 Card Edge Connector Digikey S5223 J3 44 Pin 0 156 Card Edge Connector Digikey 5223 18 4 Pin Power Header Digikey WM1626 9 4 Pin Power Header Digikey WM1626 R1 o 1 Metal Film Resistor Digikey R2 E Metal Film Resistor Digikey kOHm R3 200 Ohm Metal Film Resistor Digikey R4 200 Ohm Metal Film Resistor Digikey R5 200 Ohm Metal Film Resistor Digikey R6 200 Ohm Metal Film Resistor Digikey T1 25 Volt Audio Line Transformer Stancor A8096 T2 25 Volt Audio Line Transformer Stancor A8096 U1 Monitor Switch Digikey EG1951 U2 Voltage Regulator uA7805 220 Digikey 296 13996 5 ND Preamp Card Ref Value Description Supplier Part C1 22 nF Ceramic Capacitor Digikey 399 2006 ND C2 22 nF Ceramic Capacitor Digikey 399 2006 ND C3 22 nF Ceramic Capacitor Digikey 399 2006 ND C4 22 nF Ceramic Capacitor Digikey 399 2006 ND C5 22 uF Tantalum Capacitor Digikey 399 1531 ND C6 22 uF Tantalum Capacitor Digikey 399 1531 ND C7 0 1 uF Ce
7. If you are in 350Hz mode you may want to consider turning on the 9kHz filter This will give you much cleaner data but you will lose the frequency range below 7kHz Alternatively move the antenna to a better location further away from power lines Additional Comments The following additional notes should be known to those building or using an AWESOME receiver 1 2 3 4 5 There is an error on the preamp card the ADG441BN U8 Pin 13 should be connected to 15V but it Is not connected on the circuit board Thus it is necessary to manually solder a wire to some convenient 15V pin like the positive side of C29 Note that without this fix the system will still appear to work but some distortion will be introduced due to this error T1 and 2 on both the line recetver s motherboard and the preamp s backplane are mislabeled One of the sides is labeled 10 and Com but this should really read 1W and Com The Stancor A 8096 line transformer does not have a 10W pin VERY IMPORTANT SAFETY ISSUE Make absolutely sure when building a receiver that all pins that are attached to the 110VAC line are very well shielded and protected so that they cant be touched shorted out In the initial run of receivers the 60Hz EMI filter power switch and fuse ate placed behind a metal box the same kind usually used in wall power switches All exposed contacts are covered well with electrical tape o
8. and this should complete the setup xvi Calibration and Characterization receivers should be characterized in the field in order for data to be analyzed from site to site with a common reference The calibration should be done only when the entire unit is set up so that the effects of the particular antenna cable etc can be included All calibration should be done only when the hardware has been fully tested to work Specifically make sure the preamplifier cards are balanced To balance them use a multimeter to measure the DC voltage between the TP1 and TP2 test points on the preamp card This voltage should be zero If it is not tune the potentiometer R6 until they are equal Balancing the two branches of the amplifier circuit will ensure that the noise rejection specifically at the common mode 15 at its peak Once the circuit has been tuned put some glue over the potentiometer so that it does not shift to a different setting In addition the calibration circuit must be tuned to provide a known output before calibration can begin To do this measure the voltage between 1 the node between R46 and R48 and 2 the node between R47 and R49 Tune the potentiometer R51 until this voltage difference is 2 0 Volts peak to peak This will generate a 1 00mV RMS signal at each frequency component spaced out by 250Hz Once again put some glue over the potentiometer once this has been set to ensure that it does not shift
9. and when only the best in sensitivity is desired you can use the 921 m triangular antenna but of course this will require a lot of effort to hold in place mechanically The 10201 m2 triangular antenna is probably too big for any application unless you are able to affix it to a permanent structure but not one that is anywhere close to electromagnetic interference sources The antenna should be oriented in a consistent repeatable and documented fashion in order for data from all different sites to be compared We recommend orienting the antenna in the following fashion Align the NS antenna so that the loop is in the NS plane this can be either magnetic north or geographic north You will need a compass or a GPS device to align it properly or some way to determine direction to within a few degrees of accuracy The other antenna should then be aligned along the EW direction and the orthogonality of the two antennae should be checked with a square To ensure that the polarity of the antennae is consistent from site to site we recommend orienting the connections as follows When you are standing to the north of the EW antenna looking south at it if you follow the antenna loop from the side to the side the antenna loop should be clockwise When you are standing to the east of the NS antenna looking west at it following the connection to the connection should go clockwise Connect the antenna to the preamp using these
10. n Select Synoptic radio button Enter 00 00 00 for Start p Enter 13 00 00 for End q Enter 00 05 00 for Duration r Enter 01 00 00 for Period s Click on Add in the Select Narrowband Channel section t Click save data to hard drive u Click FTP data v Click Synoptic Cleanup w Enter NLK under Channel Name x Enter 24800 for Center Frequency y Enter 5 for Calibration Factor z Select 50Hz for sample frequency aa Select NB200 for primary filter bb Select ADC1 for A D card Select 2 for A D channel number dd Click on Add in the Set Acquisition Timing section ee Select Synoptic radio button ff Enter 00 00 00 for Start gg Enter 13 00 00 for End hh Enter 00 05 00 for Duration ii Enter 01 00 00 for Period ij Click OK 23 Click OK for Narrowband Settings GUI 24 Click Save on the main dialogue 25 Click Exit on the main dialogue 26 Restart the computer The software should startup automatically at the start of the computer and the data acquisition will begin xviii Deployment Checklist The following items are needed or recommended for any deployment Preamplifier Line Receiver Belden 1217B Cabling for preamp to line receiver Short Belden 1217B Cable for initial testing Computer set up with the following DVD writer drive DVD burning software MATLAB DAQ Software National Instruments 6034E ADC Card PC
11. AC DC regulation circuit in the line receiver and the DC DC regulation in the preamp Single cable connection between line receiver and preamp The former VLF receivers had two coaxial BNC cables one for each channel connecting the preamplifier to the line receiver The N S channel also transmitted the 35 V power signal This has been replaced with a new four pair shielded cable made by Belden the 1217B Not only has the power signal been decoupled from the transmission line for the signals but there is now only one cable instead of two and 75 2 impedance of the cable used reduces the signal attenuation for the long cable lengths Improvements in low frequency response Though previous receivers were deployed in places that required measurements of frequencies as small as 30 Hz a number of undocumented hardware changes were required in otder to achieve this response This is mostly because the older version was designed primarily to be a narrowband system optimized for the frequency range of 10 40 kHz In addition the line transformers on either side of the transmission lines had some peaking at in the frequency response at about 1 kHz and began to rolloff a lttle below that AWESOME is designed by default to work at frequencies as low as 30 Hz The newer version replaces the line transformer with a better one which has a lower cutoff Improvements in high frequency response Our receiver systems are sampled at 10
12. ADC Information Previous Nest AES b Click Add c Type in ADC1 for Unique Card Name d Type in 1 for Device Number e Under Card type select 200kHz f Click OK 9 Click on Serial Settings Serial Port Settings Motorola GPS system should use the following settings Baud rate 9600 Byte size 8 Buffer size 2048 Parity None Stop bits 1 Click OK 9 Click on Antenna Settings and enter as much information as you can about the antenna setup copy of all this data is saved in the settings file which is important to consult when studying your acquired data Antenna Properties Number of antennas R ___ Antenna impedance LI Cancel Wire gauge Wire length 1 tum Number of tums Latitude Area of 1 tum i 4 Longitude Antenna height e aj Altitude Im Antenna base lengtr Aina beangs Antenna shape Antenna descriptior 10 Click OK on the Antenna Settings Dialogue Box 11 Click OK on the Hardware information dialogue box 12 Click Communication Settings DK Network Senigo IV Have Internet Access 13 Check Have Internet Access 14 Click FTP Settings FTP Settings FTP Setting Number 0 Host IP Address vif eurcpe stanfor Username hail Host Port Number 21 Password ren Host Data Directory WLFTEST FTP file upon file completion Con
13. GPS Frequency Spectrum CH1 Spectrum 18 1 dB REF 16 1 dB 18 434 dBm E 160 000034 kHz 8 NES NN k ua RUNE OR RBH 1 Hz VBH 1 Hz ATN dB SHP 5 471 sec START 99 995 kHz STOP 100 005 kHz Motorola GPS new Frequency Spectrum DONE STOR DEV DISK CANCEL iv Hardware Schematics The following hardware schematics and layout drawings are included 1 Preamplifier Backplane Preamplifier Gain Card Preamplifier Gain Card Layout Line Receiver Motherboard Line Receiver Motherboard Layout Line Receiver Filter Card Line Receiver Sideboard xl e Electric field preamplifier card Preamp DC Biases The following diagram shows the DC biases for the preamp transistor circuit This may be useful for troubleshooting or for future design changes vi Parts List Here is parts list for the 2005 Stanford receiver VLF System Line Receiver Qty Description Supplier Part 1 Motherboard Advanced Circuits Custom Made 2 Filter Cards Advanced Circuits Custom Made 1 Sideboard Advanced Circuits Custom Made 1 External Power Supply PowerOne HAD15 0 4 A 1 Box ProtoCase Custom Made Preamp Qty Description Supplier Part 1 Backplane Advanced Circuits Custom Made 2 Preamp Cards Advanced Circuits Custom Made 1 Box Adalet JN4XH
14. a value and usually takes up to 5 minutes to converge See Clock Accuracy section XI Antenna Design The basis of the 2005 receiver is a 1 Q 1 mH antenna The antenna type is air core magnetic wire loop antenna which means it consists of a single long wire wrapped one or more times in a loop in such a way such that the total resistance of the wire loop 15 1 2 and its self inductance is 1mH This introduces a high pass cutoff of 159 Hz due to the electrical properties of the antenna Magnetic field changes induce electromotive forces in the wire inducing currents in the loop The Paschal report lays out several possible configurations of wire that meet these requirements and derives the physics of current induction They are reproduced here for convenience Some Valid Antenna Configurations Length AWG Turns Area Weight Wire mV pT Input 16 0 cm 20 47 256 cm2 0 132 30 1 m 1 20E 02 56 7 8 21 0 3215 n 0 331 kg 47 6 m 6 75E 02 1 70 m 6 11 2 89 m 0 831 kg 74 8 m 3 18E 01 4 90 m 4 6 24 01 m 2 09 kg 117 6 m 44 00 2 60 m 6 12 1 69 m 0 838 75 3m 2 03E 01 Right 8 39 m 4 6 17 60 m 2 15 kg 121 5 m 06E 00 Isosceles 27 3 2 3 186 32 m 5 56 kg 197 7 m 5 59E 00 Triangle 60 7 m 0 2 921 1 m 13 1 kg 293 1 m 84E 01 202 m 8 1 10201 m2 34 5 kg 487 7 m 02E 02 There are two shapes of antennae square and isosceles triangle The lengt
15. and Filtering r Select A D Card Sample frequercy 100 kHz y A D zard y Primary filter 5000 channel number fi r Set Acquisition Timing Continuous Synoptic Broadband timing number ee Previous Nest Add Delete Stat 2 0 Period Use this channel s timing for all channels End 2 0 0 Duration 0 Oo NARROWBAND The software supports multiple channels of Narrowband data acquisition To add a channel simply click on the add button in the Select Narrowband Channel section The save data to disk checkbox if unchecked will delete the data on the harddrive after it has been FTPed The FTP data check box will data using the specified FTP setting which can be selected from the pull down menu The synoptic clean up checkbox if checked will run the synopticCleanup bat file after every synoptic acquisition The Do Low Res check box will create a matlab file containing 1 Hz data in addition to the regular settings of this channel The spheric channel check box indicates if the channel 15 used for spheric detection The MSK modulated check box if checked will remove the phase modulation in the signal For each channel the user must specify which ADC card to acquire data from Also the user must specify which of the 2 channels usually north south or east west on the ADC card to acquire from For each channel
16. card to acquire data from Also the user must specify which of the 2 channels usually north south or east west on the ADC card to acquire from For each channel the user can specify the sample rate that data will be acquired at The 100kH data will be decimated down to this sample rate For each channel the user can specify a filter setting to be used from the filter settings created in the filter GUI For each channel the user must specify the timing schedule for this channel To add a timing schedule simply click on add and enter the times Start time The time that acquisition should start End time The time that acquisition should end Period For synoptic acquisitions the period of acquisition For continuous acquisitions the length of data contained in each file Duration For synoptic acquisitions the duration of each period For continuous acquisitions the length of data contained in each file Note for continuous acquisitions the period and duration should be the same For example start time of 3 00 end time of 10 00 period of 1 hour duration of 5 minutes will acquire data for the first 5 minutes of each hour from 3 00 to 10 00 Broadband Acquisition Settings Real T Select Broadband Channel a C 1 dth raw DK Broadband ckannel number 0 PaformFFT using Cancel Previat Next Add Delet cuf o Save datato harddrive FTP data FTP Setting rJ Synoptic Cleanup r Data Rate
17. click on the save button in order for changes to take effect Additionally the software must be restarted for the saved changes to take effect RESTORE SETTINGS This button restores the software settings to the last saved values EXIT This button will close out any current data acquisitions and end the program STATION INFORMATION This is where the user can specify the various characteristics of the station that the software is installed at With the exception of StationID and Station name the fields in this GUI do not directly affect the data acquisition It should be used as reference when studying data acquired Station name indicates the directory that the files will be FTPed to For example if Stanford is entered as Station Name the files will be FTPed to the a directory called Stanford When narrowband data acquired it will create matlab filename accotding to the new filename format XXYYMMDDHHMMSSZZZ ACCT mat XX Station ID from Station Information Dialogue Box YY Year MM Month DD Day HH Hour MM Minute SS Second ZZZ Transmitter Callsign A zero based index of the ADC card that was used CC zero based index of the software channel number that was used T Amplitude Phase or Lo High Resolution A corresponds to Lo resolution 1hz sampling rate amplitude B corresponds to Lo resolution 1hz sampling rate phase C corresponds to high resolution amplitude D corresponds to high resolution phase
18. configurations Design of an apparatus to physically support the antenna loops should be based on the specifics of the site the weather antenna size ground condition length of setup etc However here is shown a sample design that has been used for the 8 39m triangular base antenna This design is faitly easy to set up however may not be so durable for high winds ot extreme weather conditions As such it is only recommended for sites that will not see overly extreme conditions or that will be monitored on a regular basis by someone who can repair it if it breaks down The next page shows pictures of the antenna The triangular antenna features a single vertical mast axxifed to the ground via a wooden board that is bolted down Four guidewires two attached just below the top of the mast two about halfway up the mast stabilize the mast and are staked into the ground so that guidewire is taut but not too tense Finally the four antenna loops are locked into place at the top of the mast stretched out aligned to the proper directions and then staked into the ground Antenna Mast with Guidewires Base of Mast Secuted to Ground Here is a complete parts list for this particular antenna design Function Part Description Qty elevate antenna loops on mast Aluminum poles square 1 25 OD x 6ft 3 Antenna wire loops join sections of mast 18 8 SS hex cap screw 1 4 20 x 3 6 fix cap screws to mast 18 8 SS Hex nylon insert l
19. in fall 2004 during which time the support structures were finalized and this documentation packet was formed At that point the receiver was named the Atmospheric Weather Educational System for Observation and Modeling of Effects or the AWESOME receiver It was named as such because it arose out of a partnership between the VLF group headed by Umran Inan and the Solar Physics group led by Phil and Deborah Scherrer Its primary purpose originally was to setve as a tool for educational outreach in schools across America and eventually the world From this point on the receiver will be referred to as the AWESOME monitor Though based on previous designs the newest version adds a number of new improvements and modifications over the old VLF receivers to be highlighted later The rest of this packet will discuss the design use and performance of the 2005 receiver Note that this documentation report will focus on specific wotking and use of this design and implementation including the receiver electronics all the supporting hardware and software information needed to build and deploy etc For a more technical report on the design criteria for VLF receivets performance calculations etc refer to Evans Paschal s report The Design of Broad Band VLF Receivers with Air Core Loop Antennas This report and its conclusions laid the groundwork for some of the most important aspects of the AWESOME monitor The data from the 2005
20. noise characterization Emergency help contact information Morris Cohen 650 799 3674 Packard Room 12 650 725 8440 Jeff Chang 650 814 0494 Packard Room 30 650 723 1460 Umran Inan 650 804 0928 Ev Paschal 253 732 6910 Maps Cable ttes Spare fuses Small machete for clearing debris Walkie talkie pair Wood screws nails T squate XIX ix Troubleshooting Guide This guide will walk you through some of the common things that will go wrong should the receiver not function as it is supposed to Diagnosing and fixing the problem may require the following Oscilloscope function generator dummy loop soldering iron spare parts For a given problem follow each step in order one by one until the problem is solved PROBLEM The blue light on the line receiver does not light up when it is switched on DIAGNOSIS The 15 power supply to the motherboard is not functioning This may be due to a failed power supply a short in the circuit ot a loose connection SOLUTION 1 2 Make sure the power cord to the wall is plugged in correctly Turn off the line receiver and unplug the four pin power connector that runs from the HAD15 power supply to the mother board The end of the connector that plugs into the board has four pins on it The single pin nearest the straight edge is ground Next to it is an empty slot followed by the 15V and the 15V which is closest to the 45 degree angle side Using a mu
21. not been properly shut down problems with PC mouse operation may occur This is because the GPS card is communicating to the computer s serial port while the computer 15 initializing its drivers If this occuts turn off the Line Receiver or disconnect the setial cable and reboot the computer Wait for the computer to enter Windows before reconnecting the Line Receiver If the GPS Console program does not seem to be working at all sometimes another program is needed to initialize the COM port Use a free serial port monitor Windmill Comdebug to open then close the port Serial settings Data bits 8 Parity Bit none Stop Bit 1 Baud 9600 Hardware Source Synergy Systems www synergy gps com Code System FPGA Specifications FPGA The system uses an FPGA to generate sampling signals Manufacturer Altera Corporation Model EPM7064AELC44 Package Type PLCC 44 Pin IO Voltage 3 3 V Internal Voltage 3 3 V Speed Grade 3 to 7 Source Clock The HAIL FPGA is driven by a 10 MHz oscillator Manufacturer Vectron International Model VTA1 1B1 10MHz is just a lower profile version it would also work Frequency 10 000 MHz Stability 41 ppm Waveform 0 V 3 0 V CMOS square wave Features Voltage controlled trim Verilog Top Level Module LOGIC 100 kpps Sampling Module GPS_PULSE_100KPPS v The HAIL FPGA controls the 100 kpps sampling frequency It uses the
22. power supply inside the line receiver If using in an area that does not provide 60 Hz 110 V power you will need to find a way to convert your power or to drive the line receiver s DC input voltages directly from an external source The voltages 15 V are delivered along the same cable that brings the signals from the preamp the shielding of the cable pairs enables this to be possible without degradation of the data Finally the line receiver controls and activates the calibration circuit in the preamp by sending a 15 V power signal over the cabling The FPGA on board also controls this activating the calibration circuit at predetermined internals by turning on a transistor driver circuit Input from Clip Light Preamp Indicator Input Anti Clipper and An jp Output to Coupling Comparator Aliasing ADC Card Transformer Filter Calibration Output to A utput to m Circuit Serial port Driver t 15V 10 MHz GPS Oscillator Antenna Figure 4 Line Receiver Block Diagram The data is usually digitized with a card installed in the PC The card used is made by National Instruments and goes into a PCI slot in the computer Alternatively PCMCIA version is available for a laptop computer The PC has installed software created by the group that is capable of producing raw MATLAB data files demodulating and breaking down the data for selected frequencies narrowband studies and sending the info
23. receiver is often used in one of two ways Broadband analysis and narrowband analysis In broadband analysis the entire frequency spectrum between the cutoffs is retained and often presented in the form of a spectrogram Shown here is an example of a spectrogram created by MATLAB It shows the frequency content ovet a 10 second snippet The red areas indicate strong signals at that frequency and that time while the yellow and blue areas indicate a weak and very weak presence at those frequencies 4 10 5 x 45 4 3 5 15 05 8 5 0 1 2 3 4 5 6 7 8 iz Time Frequency EX In this example there is a strong single frequency signal at 5 kHz injected externally at the input for the first seven seconds indicated by the horizontal red line that then drifts around for the last few seconds turning the knob on the signal generator There 1s also a broadband signal appearing once second this was a test calibration signal to be discussed later The noise floor is a bit elevated around 10 kHz as can be seen by the yellowing there The color scale is in decibels This spectrogram represents one channel of data Narrowband analysis is done a little differently The data stream is filtered out except for one very small frequency band usually corresponding to a transmitter frequency Using fourier analysis and demodulation the amplitude and phase at that frequency can be determined and recorded this
24. small antenna and outputs its signal to a laptop for quick characterization of electromagnetic environment The 2005 VLF receiver includes a fully specified and repeatable design for a hum sniffer Ease of duplication and change The AWESOME monitor includes a complete parts list including price part number and manufacturers Also included is software to reproduce the circuit boards box and every other parts For future VLF receiver needs as well as for future design changes individual portions can be modified and change without redoing the entire system from scratch as was done for this iteration E field preamp The AWESOME monitor can be adapted for picking up electric field signals instead of along with magnetic field signals through the use of a dipole whip antenna and a different preamp card This is detailed in the later sections lii Sampling Clock Feedback for Accurate Phase Information One of the most important features of the 2005 VLF receiver is the ability to produce a very exact 100 kHz signal for sampling This signal is synchronized with a GPS signal and has very small error When the error is small enough the data retrieved can be compared from site to site and in addition the phase information gathered in the narrowband analysis becomes much more exact Older versions used an external GPS clock made by TrueTime to provide the 100 kHz signal but the 2005 model introduces a frequency locked loop to achieve
25. source 10 MHz clock and counts up to 100 to create a 100 kHz square wave signal The 100 kpps signal is aligned every second to the 1 pps input signal from the Motorola GPS board GPS Communication Module LOGIC v GPS communication signals are routed through the FPGA Currently nothing is done to the signals but it does allow for future control over the Motorola GPS board Calibration Tone Module CALIBRATOR v Timing to turn on the calibration signal see Calibration Circuit is controlled by the It uses a series of counters driven by the GPS 1 pps signal to turn on the cal signal periodically There are currently 3 settings for the calibration period These are controlled by the auxiliary jumpers on the motherboard No jumpers normal 300 second period operation AUXA once minute for 0 2 seconds each time AUXB 400 second period Currently not supported DO NOT place a jumper on AUXB unless you have read the additional notes section there 15 an error on the circuit board Note do not place jumpers on AUXA and at the same time Clock Adjustment Module CLOCK ADJUST v To ensure accurate sampling with the 100 kpps signal the FPGA controls the level of the voltage trim on the 10 MHz source clock Sending values to an external DAC the FPGA detects once a second if the count to 100 is short or over and adjusts the value to the DAC accordingly The value eventually converges to
26. the user can specify the Sample frequency that data will be acquired at The 100kHz data will be decimated down to this frequency For each channel the user can specify a filter setting to be used from the filter settings created in the filter GUI For each channel the user must specify the timing schedule for this channel To add a timing schedule simply click on add and enter the times Start time The time that acquisition should start End time The time that acquisition should end Period For synoptic acquisitions the period of acquisition For continuous acquisitions the length of data contained in each file Duration For synoptic acquisitions the duration of each period For continuous acquisitions the length of data contained in each file For example start time of 3 00 end time of 10 00 period of 1 hour duration of 5 minutes will acquite data for the first 5 minutes of each hour from 3 00 to 10 00 Note The FTP pull down menu has been disabled since we do not allow multiple FTP settings un the current version Narrowband Acquisition Settings r Real Time Processing DK Select Nerowband Channel Send kull Bandwidth Narrowband Channel Number Zl Sand Fel Bane dni pla Cancel Superposed FFT Setting Epoch Settin Next Add Delete Number Naber Number Channel Name Call Sian NLK yz Center Frequency 40000 Calibration F actor SaveDatato Disk FTP Data
27. two for the antenna signals one for the power signals one for the calibration signal Each pair is shielded to prevent crosstalk and interference a Signal Differential Adjustable Transformer Amplifier Suppression Filter and Gain Input from Antenna Output Output to Line Coupling Receiver Transformer Figure 3 Preamplifier Block Diagram Preamplifier From Outside Open Preamplifier Box The line receiver s operations are noticeably more complicated than the preamp s The line receiver should be placed 100 ft or more from the preamplifier through a shielded cable so that the electronics in the line receiver does not emit radiation that couples into the antenna The line receiver must be placed close to a computer which can record the data coming from it The line receiver serves many functions including signal processing digitization control GPS management power management and system calibration The line receiver is placed in a custom built box though it is not designed for outdoor use In processing the signal the line receiver includes a clip protection circuit which clips the top of signals when they get too strong and sets of an indicator light If calibrated correctly though this should only be triggered in the event of exceptionally strong signals or an electrical failure The most important part though is an anti aliasing filter For most group applications the data is sampled at 10
28. 0 kHz which is why the anti aliasing filter is set at 40 kHz or so The new receivers implement this filter with a sharper circuit LTC1562 which has both a flatter response in passband and a sharper brick wall response As a result the new anti aliasing filter raises the bandwidth of useful data to 45 47 kHz The filter cuts off at 47 kHz and reaches 100 dB of attenuation by 55 kHz ensuring that data up to 45 kHz is free of aliasing These two pictures show the improved anti aliasing filtering of the AWESOME monitor The red line indicates the amplitude and the blue line indicates the phase Old VLF Receiver Frequency Response New Receiver Frequency Response Elimination of external GPS clock The older VLF systems used a GPS receiver made TrueTime The key advantage to it was that it provided not only the 1 Hz GPS signal but also a 100 kHz signal used for sampling that is synchronized with the GPS signal and thus very exact as described earlier this is important in order to get accurate phase information and to compare data from site to site In the 2005 VLF receiver this has been eliminated and replaced with a Motorola GPS receiver contained within the line receiver Though the Motorola GPS receiver does not generate the 100 kHz GPS synchronized clock a frequency locked loop consisting of a 10 MHz oscillator an FPGA and a D A converter all this is detailed later generates the 100 kHz sampling signal within t
29. 0 kHz thus the anti aliasing filter should be fixed between 40 and 50 kHz A pair of identical filter chips 12 poles total takes care of that filtering Line Receiver Front Line Receiver Back Line Receiver Inside One of the key requirements for the 2005 receiver 15 very high accuracy sampling in order to synchronize the sampling in different systems and provide precise phase information in narrowband analysis This requirement is met by providing the ADC card with a low skew low draft clock The line receiver does this by using a GPS locked signal and a trim adjustable 10 MHz oscillator Using the GPS timing signal 1 Hz and a feedback circuit the 10 MHz clock is adjusted so that it is as accurate as possible The 100 kHz sampling signal is generated from this accurate clock The details and performance characteristics of this are included later The GPS signal needed for this circuit comes in from an antenna and is attached to an on board card made by Motorola The GPS antenna does not need to be in a quiet location but it should have a clear view of much of the sky in order to communicate with GPS satellites An FPGA in the line receiver communicates with the Motorola board and uses it to synchronize the sampling clock and to provide a time stamp for all the data through a serial port The line receiver is also responsible for providing power to the preamplifier The power is generated from 60 Hz 110V AC power by an external
30. 155 ND D1 1N4005 Diode Digikey D2 1N4005 Diode Digikey D3 1N4148 Diode Digikey JA 12 Pin Power Header Digikey WM1629 J2 50 Pin Right Angle Header Digikey AHZ50K j3 0 1 Jumper Header Digikey 4 103240 0 j4 44 Pin 0 1 Card Edge Connector Digikey 1223 15 10 0 1 Protected Header Digikey A26268 J6 44 Pin 0 1 Card Edge Connector Digikey 51223 J7 0 1 Jumper Header Digikey 4 103240 0 J8 0 1 Jumper Header Digikey 4 103240 0 J9 0 1 Jumper Header Digikey 4 103240 0 J10 0 1 Jumper Header Digikey 4 103240 0 L1 22 uH Inductor Digikey 1530B225 L2 22 uH Inductor Digikey 1530B225 L3 22 uH Inductor Digikey 1530B225 L4 22 uH Inductor Digikey 1530B225 Q1 2N3906 PNP Transistor TO 92 Digikey Q2 2N3904 NPN Transistor TO 92 Digikey R1 4 7 kOhm 1 Metal Film Resistor Digikey R2 nn 1 Metal Film Resistor Digikey R3 N A Does not exist R4 47 Ohm 1 Metal Film Resistor Digikey R5 N A Does not exist R6 N A Does not exist R7 10 kOhm 1 Metal Film Resistor Digikey R8 N A Does not exist R9 75 Ohm 1 Metal Film Resistor Digikey R10 75 Ohm Metal Film Resistor Digikey R11 953 Ohm 1 Metal Film Resistor Digikey R12 1 kOhm Metal Film Resistor Digikey R13 250Ohm Metal Film Resistor Digikey R14 250 Ohm Metal Film Resistor Digikey R15 1 kOhm Metal Film Resistor Digikey R16 1 kOhm Metal Film Resistor Digikey R17 1 kOhm Metal Film Resistor Digikey R18 1 kOhm 1 Metal Film Resistor Digikey R19 1 kOhm 1 Metal Film Resisto
31. 1N4148 Diode Digikey D2 1N4148 Diode Digikey D3 1N4148 Diode Digikey JA 0 1 Jumper Header Digikey 4 103240 0 14 0 1 Jumper Header Digikey 4 103240 0 JP2 0 1 Double Jumper Header Digikey 4 103240 0 L1 10 uH Inductor Digikey 2 10 uH Inductor Digikey Q1 2N4250 PNP Bipolar Transistor Digikey PN4250 ND Q2 2N4250 PNP Bipolar Transistor Digikey PN4250 ND Q3 2N4250 PNP Bipolar Transistor Digikey PN4250 ND Q4 2N4250 PNP Bipolar Transistor Digikey PN4250 ND Q5 2N4250 PNP Bipolar Transistor Digikey PN4250 ND Q6 2N4250 PNP Bipolar Transistor Digikey PN4250 ND Q7 2N4250 PNP Bipolar Transistor Digikey PN4250 ND R1 ae 1 Metal Film Resistor Digikey K 267 T R2 Ohm 1 Metal Film Resistor Digikey K 200 a ios R3 Ohm 1 Metal Film Resistor Digikey K 200 5 iss R4 Ohm 1 Metal Film Resistor Digikey K 1 75 T R5 Ohm 1 Metal Film Resistor Digikey K R6 500 Ohm Potentiometer Digikey R7 1 Metal Film Resistor Digikey K 22 6 ais R8 Ohm 1 Metal Film Resistor Digikey 9 09 dio Me R9 Ohm Y Metal Film Resistor Digikey K 7 48 7 v R10 Ohm Metal Film Resistor Digikey K R11 1 MOhm Metal Film Resistot Digikey R12 p 1 Metal Film Resistor Digikey K a 48 7 xs R13 Ohm Metal Film Resistor Digikey K R14 1 MOhm 1 Metal Film Resistor Digikey R15 nn Metal Fi
32. 2 Set up icons on the desktop for the DAQSoftware program for Matlab for the DVD burning software and for the Data folder 3 Create a text file with the sentence A Reboot has Occurred Place this text file in the programs startup folder in your Windows XP start menu 4 Place a shortcut to the StanfordDAQ program in the programs startup folder in your Windows XP start menu 5 Open the line receiver in the red box and make sure that all screws are tightened all cards are in place all connectors ate in tightly the jumper settings are correct Place the cover on the line receiver but do not screw it shut until testing and calibration is complete as you will need access to the inside of the line receiver Make sure there is a working fuse already installed 6 Attach the line receiver to the computer with two cables nullmodem serial cable and an ADC cable which has blue 50 pin connectors on the ends Both these slots should be labeled on the back of the preamplifier and should fir it exactly one slow on the back of the acquisition PC 7 Connect the GPS antenna via the N Type cable to the connector on the back of the line receiver 8 Plugin and then turn on the line receiver 9 Open the VLF DAQ program on the PC Within a second or two you should see all the GPS coordinates times displayed If the system has been cold for a long time it may take a few minutes for the GPS card to locate enough GPS receivers to know
33. A 100804 Qty Description Supplier Part 1 Vic100 GPS Timing Antenna w Pipe Clamp Synergy Systems 10001339 1 GPS N connector Cable 50m Synergy Systems 1 10ft 1 5 in PVC piping with connector parts Home Depot Cable Assembly Qty Description Supplier Part 1 Four Twisted Pair Shielded Cable 250 ft Belden 1217B 2 Amphenol 12 Pin Cable Connector with Sockets Digikey 97 3106 20 275 Antenna Qty Description Supplier Part P Wire 14 AWG 2 Amphenol 3 Pin Cable Connector with Rocker Digikey MS3106R 10SL 3S A D System Qty Description Supplier Part 1 NIDAQ Card 6034E Natio al 187576C 01 Instruments 1 50 Pin Cable SH6850 776784 01 Instruments e e ine Receiver Motherboard Ref Value Description Supplier Part C1 4 7 nF Ceramic Capacitor Digikey 2 4 7 nF Ceramic Capacitor Digikey C3 10 uF Tantalum Capacitor Digikey 399 1335 ND C4 4 7 nF Ceramic Capacitor Digikey _ 5 4 7 nF Ceramic Capacitor Digikey 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C7 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C8 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C9 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C10 47 nF Ceramic Capacitor Digikey 495 1069 1 ND C11 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C12 0 33 uF Ceramic Capacitor Digikey 399 2174 ND C13 1 0 uF Tantalum
34. Capacitor Digikey 399 1337 ND C14 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C15 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C16 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C17 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C18 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C19 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C20 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C21 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C22 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C23 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C24 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C25 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C26 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C27 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C28 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C29 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C30 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C31 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C32 Small Optional Typically left out C33 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C34 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C35 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C36 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C37 1 0 uF Tantalum Capacitor Digikey 399 1337 ND C38 0 1 uF Ceramic Capacitor Digikey 399 2155 ND C39 0 1 uF Ceramic Capacitor Digikey 399 2
35. E MODIFY FILTER SETTINGS After data is acquired we would like it to be filtered This is done through the filter GUI To add a filter simply click on the Add button then click on the Filter from File A dialogue in which the user can select a filter file will be brought up The filter file simply contains the filter coefficients of a filter these filter files can be created through matlab Sample filter files are included on the filter folder For each filter setting the user should specify a filter name Create Modify Filter Settings Filter number o OK E Unique filter name 5000 Hz Cancel Number of taps p Cutoff frequency Hz Sample frequency Hz Decimate to p Hz Remove ous Add Delete BROADBAND The software supports multiple channels of Broadband data acquisition To add a channel simply click on the add button in the Select Broadband Channel section The save data to disk checkbox if unchecked will delete the data on the harddrive after it has been FTPed The FTP data check box will FTP data using the specified FTP setting which can be selected from the pull down menu Note that FTPing of broadband data is not recommended because of the size of the files The synoptic clean up checkbox if checked will run the synopticCleanup bat file after every synoptic acquisition The user may edit synopticCleanup bat file to do anything For each channel the user must specify which ADC
36. I NI DAQ Software comes with 6034E Monitor keyboard mouse Surge Protector Powerstrip Nullmodem Serial Cable GPS Antenna N Type Cable for connection to GPS Antenna Short N Type Cable for testing Portable oscilloscope Portable function generator Antenna post parts specified for 4 39m base 2 19m height 6 turn isosceles triangle Aluminum poles 3 14 20 bolts 6 14 20 nylok nuts 6 5 16 eyebolts 2 5 16 nuts 6 long guide wires with 5 16 eyebolts and turnbuckle 2 Carabiners 2 Terminal lugs to fit 6 32 screw nut 4 Metal stakes 8 Plastic rollers 4 Plastic guards 4 Antenna wire loops 2 Toolkit including pliars wrench hammer screwdrivers wire strippers snips spackle Preamp mounting parts Soldering iron and solder Dummy loop Cable connection for antenna to preamplifier with 6 32 screwbolts and nuts 1 4 PVC piping and hose clamps for securing GPS antenna Compass for aligning antenna Handheld GPS Schematics and documentation Sharpie for labeling DVDs Blank DVDs Spare filter cards preamp cards programmed FPGA GPS card BNC cables banana plugs alligator clips wire Multimeter Power cables for computer monitor line receiver Cable to connect line receiver to ADC card Camera Tape measure Electrical tape Caulk or other form of Heavy duty putty Drill Bubble level for aligning antenna Plumb for aligning antenna Hum sniffer for antenna spot selection and
37. R6 k S Metal Film Resistot Digikey 40 2 A x R7 kOhm o Metal Film Resistor Digikey 60 4 T R8 kOhm Metal Film Resistor Digikey R9 5 kOhm Metal Film Resistor Digikey R10 47 Ohm Metal Film Resistor Digikey 1 Metal Film Resistor Digikey 56 2 5 R12 kOhm Metal Film Resistor Digikey 105 2 3 kOhm o Metal Film Resistor Digikey 4 5 kOhm Metal Film Resistor Digikey R15 bd Metal Film Resistot Digikey 48 7 o ae 6 kOhm Metal Film Resistor Digikey 7 20 kOhm Metal Film Resistor Digikey R18 a Metal Film Resistor Digikey R19 k zu Metal Film Resistor Digikey R20 3 kOhm Metal Film Resistor Digikey R21 3 9 kOhm Metal Film Resistor Digikey R22 4 kOhm Metal Film Resistor Digikey R23 3 kOhm Metal Film Resistor Digikey R24 3 9 kOhm Metal Film Resistot Digikey R25 13 7 Metal Film Resistor Digikey kOhm R26 Metal Film Resistor Digikey kOhm R27 215 Metal Film Resistot Digikey kOhm R28 Metal Film Resistor Digikey kOhm R29 Bee Metal Film Resistor Digikey kOhm R30 Film Resistor Digikey kOhm R31 10 kOhm Metal Film Resistor Digikey R32 10 kOhm Metal Film Resistot Digikey R33 10 kOhm Metal Film Resistor Digikey R34 10 kOhm Metal F
38. Stanford University Electrical Engineerine Space Telecommunications and Radioscience STAR Laboratories tmospheric W eather ducational ystem for O bservation and odeling of Electromagnetic effects Documentation By Morris Cohen Last modified August 30 2005 Vi vil vili xvi 1 xxii Table of Contents Introduction to the Stanford University 2005 VLF receiver Improvements in the Stanford University 2005 VLF receiver Clock accuracy Schematics Preamp DC biases Parts list Cabling pin connections Calibration circuit GPS Communication FPGA code Antenna design Dummy loop design Hum Sniffer Design Electric field reception Testing and set up Calibration and characterization instructions Using the software written by Eddie Kim Deployment checklist Troubleshooting Guide Additional comments Undocumented changes Acknowledgements User Comments 1 Introduction to the Stanford University 2005 Receiver The Stanford University Electrical Engineering Department s Very Low Frequency group is engaged in studies of electromagnetic phenomenon in the ionosphere and magnetosphere One of the primary ways of studying these effects is through the use of ultra sensitive ground based receiver instruments consisting of an antenna or two and electronics to process the antenna s signal The electronics is designed to capture fre
39. ata to a remote site after it is acquired and processed do this the user must add a FTP setting in this GUI We will call the computer that we would like to FTP data to the FTP computer For each FTP computer the user must enter the FTP computer s IP address i e vlf europe stanford edu port number user name password FTP times and directory you would like the data to be FTPed to For each FTP setting the user should give a name to this setting The user must also enter the time of the day that they would like the FTP to begin and end If all the files are FTPed before the end time the FTP thread will simply close before the end time If the files are not FTPed within the allotted time frame the FTP will close and finish up the following day during the next FTP time We currently support only one FTP setting SFTP Settings t FTP Setting Number o FTP Name OK Host IP Address Username Host Port Number p Password Host Data Cirectory FTP file upon file completion Convert to mat FIP file starting at 0 0 0 Delete bin file upon success ul FTP end at 0 0 0 Delete directories after 20 days Previous Nest Delete NETWORK SETTINGS We can control the software over the internet without physical being at the actual computer We will call the computer we would like to control the remote computer and the computer we would like the control the rem
40. ce per second Stanford EW Antenna DIAGNOSIS The signal is getting cut off somewhere after the preamp card but before H the filter card in the line receiver SOLUTION 1 the Belden cable is screwed in completely on both the preamp side and the line receiver side 2 Make sure the gain setting light comes on inside the preamp Note that you may have to turn the knob all the way around to see it If it does not come on you may have a bad Belden cable Use a multimeter or function generator scope to check that all 12 connections go through the cable note that there are two unused pins on the connector and that no signal is shorted to another one Stanford NS Antenna PROBLEM The data looks like this on both 8 channels note that this is similar to the last one except the 40 50kHz band shows no 8 9 5 characteristic here e o 8 10 12 SOLUTION The signal is getting cut off after Stanford EW Antenna 8 the filter card It is possible that the filter cards are not functioning or have been removed Try 20 Frequency kHz replacing them 8 10 12 Time seconds after PROBLEM The data looks like this on both channels DIAGNOSIS The antenna signals are not reaching the input to the preamplifier SOLUTION Make sure the antenna connectors are firmly plugged in that their signal runs smoothly to the pr
41. ceiver GPS Receiver T ina Ranaitrar The line receiver gets VLF signals from 2 antennas There is usually one antenna in the North South orientation and another in the East West orientation These signals are sent to a 200kHz ADC attached to the PCI slot of the computer The ADC will capture data from each of the 2 antennas at 100kHz each The signal from the GPS 15 fed into the ADC card The VLF DAQ software controls precisely when the system should acquire broadband and natrowband data Upon data acquisition various user specified signal processing can be performed on the data The data is then converted to MATLAB format and may be sent to another computer via FTP The DAQ is designed to be robust even when multiple channels of synoptic broadband continuous broadband and narrowband are being run simultaneously Because different users may want to use the software for different applications the software was built with scalability in mind For example user defined scripts can be run after acquisition of data DAQ GPS Receivet Line Receiver North South Receiver East West Receiver Installing the Software SYSTEM REQUIREMENTS 1 Intel Pentium 4 processor PC 2 Microsoft Windows XP 3 512 MB Ram 4 10 GB Drive for broadband acquisitions RECCOMENDATIONS The software is a very CPU intensive program during data acquisitions so it is recommended that all other CPU heavy programs be tur
42. clip chips in the line receiver on each channel and the amplifier cards in the preamp The modular design also enables a one channel system to be converted to two channel with much more ease The input and connections to the box were all made with Molex power plugs rather than permanent soldering Though a slight contact resistance is introduced replacing a solder joint resistance the main boards in each box can be detached from its surroundings and removed in a matter of seconds for easy replacement testing or debugging New repeatable dummy loop design A device called a dummy loop emulates the impedance of the antenna and allows test signals to be injected into the VLF system The previous VLF receiver did not include an accompanying dummy loop design so dummy loops were often built by hand individually part of the AWESOME package a new repeatable dummy loop has been completely designed and specified and a sufficient number will be made so that VLF systems can be readily tested when needed New repeatable antenna design The support structure for the wire loop antennas was previously not documented and often built ad hoc Accompanying the 2005 VLF receiver is a repeatable clearly specified method for building two orthogonal antennas and a support structure New repeatable hum sniffer design Site selection is facilitated by the use of a hum sniffer a miniaturized portable version of the system The hum sniffer uses a
43. d examples directory The remote computer must download this batch file when step 7 is executed For the first install of this software the remote computer will look somewhere in HAILSoftwate for the DownloadNewSoftwareNext bat file For example if the remote computer is in Taylor the Taylor computer will look in CAHAILSoftwareDownloads Taylor N HAILSoftware of the remote computer for the batch file Thus it is imperative that this batch file is placed in this directory We should make sure that DownloadNewSoftwareNext bat contains the correct commands The first line mkdir creates the directory on the remote computer in which the software will be installed to The next set of lines download the necessary files into the install directory For example c HAILSoftware hftp_get exe HAILSoftwarehftp get cfg DAQ_SoftwarePackage c VLF_DAQ dailyCleanup bat will copy eNDAQ SoftwarePackage dailyCleanup bat of the server computer into c dailyCleanup bat of the remote computer IMPORTANT NOTE The drive letter that the remote computer FTPs into must be the same drive that contains NDAQ SoftwarePackage In hail stanford edu all incoming FTPs are directed to EX Thus we must place the DAQ SoftwarePackage directory in the EA After all the program files are copied the batch file has the following line c HAILSoftware hftp_get exe c HAILSoftware hftp_get cfg DAQ_SoftwarePackage c VLF_DAQ DownloadNewSo
44. eamp card Try attaching a dummy loop to the input instead of the antenna and inject signals using it If you can see these s 30 g u Frequency kHz 3 s S Stanford NS Antenna Stanford EW Antenna 6 8 10 12 Time seconds after signals at the output of the line receiver then this either means the wiring from the antenna to the preamp is bad incorrect or that the antennae themselves may have broken gotten a discontinuity PROBLEM The data looks like this on both channels DIAGNOSIS You have too much gain so the receiver is clipping This will likely be accompanied by the red lights above the BNC connectors on the front of the line receivet turning on SOLUTION Turn down the gain in the preamplifier 30dB should almost never be used and 20dB only for particularly special cases 10dB and OdB are usually the best modes PROBLEM The data has some bizarre horizontal stripes and dark light pattern in it looks like the EW channel in this spectrogram DIAGNOSIS This is generally caused by 60Hz noise infecting the circuit Frequency kHz Frequency kHz Frequency kHz H H Stanford NS Antenna 8 10 12 Time seconds after T 20 Stanford NS Antenna 8 10 12 Time seconds after SOLUTION If the 30Hz boost jumper on the preamp card is out put it back in The 30Hz boost should be turned off at this site
45. eamplifier s electronic operation is relatively simple compared to the line receiver s This is intentional in order to minimize interference into the antenna The main amplification in the preamp comes from a differential amplifier designed with discrete transistors very important component though is a custom built transformer between the antenna and the transistors that closely matches the 1 Q resistance of the antenna to the small signal resistance of the transistor circuit Following the transistor amplifier a number of op amps buffer the signal set the low frequency response cutoff and the gain An RFI radio frequency interference suppression circuit is added to the front end Made from an LC low pass filter this circuit ensures that high frequency signals like AM FM radio broadcast do not affect the electronics The preamp also includes a calibration circuit to determine the frequency response of the system The calibration circuit is described in detail in a later section but it works by injecting a test signal at the very front end of the preamplifier and the output of the receiver could be read to determine the system s frequency response The calibration circuit is activated by the line receiver which provides power to run it The preamp is placed inside a NIMA 4 rated weather proof box since it is normally placed outdoors The preamplifier is connected to the line receiver through a cable that has four pairs of conductors
46. elpful advice and consultations Robert Moore Eddie Kim for help in updating the acquisition software for use in the new receivets Jeff Chang for lots of good suggestions and general help around the lab Joe Payne For advice on the anti aliasing filter card and GPS card xxii User Comments Use these pages for keeping your own comments about the Stanford 2005 VLF Receiver
47. es a pseudorandom sequence at 8 192 MHz The pseudorandom sequence has a Foutier content consisting of uniform height spikes spaced out at 250 Hz This sequence is applied to the input lines of the preamplifier It is large enough to overwhelm incoming antenna signals but small enough not to clip the electronics The calibration signal passes through the entire system By isolating the 1 second long calibration signal and taking the FFT it is possible to map out the VLF receiver s response at discrete multiples of 250 Hz The sample spectrogram in the introductory section shows what the calibration data looks like in the data each vertical red stripe is a calibration tone Using a seties of short acquisitions it is thus possible to characterize the system in all possible modes Detailed instructions can be found in the calibration section The calibrator on each preamplifier card must be tuned to provide a known output The process of tuning can be found in the calibration section ix GPS Communication Prepared by Justin Tan GPS Timing Card GPS Timing for the new system is internal to the Line Receiver This reduces equipment costs and bulk Manufacturer Motorola Model 12 Timer GPS Antenna Any antenna approved for the Motorola M12 Timer card is acceptable The choice depends on the distance to the antenna and the particular application The antenna of choice for the system is the VIC 100 Timing A
48. f the VLF receiver s outputs Here is a list of the recordings you should make in calibration mode 1 Both preamp cards inserted 2 NS preamp card removed 3 EW preamp card removed 4 Antenna replacing dummy loop These four recordings should be taken using the preamp settings you intend to leave it in as well as any setting you think may be used in the future So if you re going to leave it at OdB gain mode but may in the future increase the gain to 10dB you will need to take double the recordings In addition repeat for any extra preamp cutoff settings BOHR 350Hz IRH that may be used Save all the calibration data and burn it to a CD or DVD Also place the recordings in a folder called Calibration and store it in the VLE DAO folder xvii Using the Software Very Low Frequency Data Acquisition Software User Manual Robert Moore Edward Kim Revised 6 March 2005 Table of Contents Introduction 3 Installing the Software 4 Overview of the Software 5 13 Sample Walk Through of a Simple Acquisition 14 25 Introduction VLF DAQ stands for Very Low Frequency Data Acquisition It is a data acquisition software designed for capturing and processing broadband and narrowband signals It works in conjunction with a TrueTime GPS receiver and 1 or more ADC cards in the PCI slot Though many different hardware configurations are possible with the software the most common setup is illustrated below North So th Re
49. ftware bat This line should be included in the batch file only for the FIRST installation of the software package Any subsequent updated of the software should not contain this line This line will update the DownloadNewSoftware bat file that is run on the remote computer anytime update new software is called from the Communicator The new DownloadNewSoftware bat file found in DAQ_SoftwarePackage directory will instruct the remote computer to look for DownloadNewSoftwareNext bat file in c VLF_DAQ from now on instead of c HAILSoftare Thus in subsequent updates of the software the remote computer will look in the VLF_DAQ directory for DownloadNewSoftwareNext bat file instead of the HAILSoftware Directory The rest of the lines will download the filter files and create the necessary directories for the program to run correctly 5 Run Demodulator exe on the remote computer 6 Run Communicator exe on the server computer connection should be established between the 2 computets on the Communicator software 7 On the server computer make sure the connected remote computer is checked and then select Download New Software from the pull down menu and then click administrator send 8 The remote computer will download DownloadNewSoftwareNext bat file from somewhere in the cA Software directory After the file has been downloaded DownloadNewSoftwareNext bat file will be executed on the remote computer The new soft
50. ges shows a schematic for the dummy loop and a complete parts list Each dummy loop has two input circuits into it allowing separate signals to be injected into the different channels Below you will also find pictures of a fully built dummy loop and a parts list Dummy Loop Electrical Components Ref Value Description Supplier Part C1 0 1 uF Ceramic Capacitor Digikey C2 0 1 uF Ceramic Capacitor Digikey R1 10 kOhm 1 Metal Film Resistor Digikey R2 1 1 Ohm 1 Metal Film Resistor Digikey R3 10 Ohm Pot 10 Turn Potentiometer Digikey R4 10 kOhm 1 Metal Film Resistor Digikey R5 1 1 Ohm 1 Metal Film Resistor Digikey R6 10 Ohm Pot 10 Turn Potentiometer Digikey J1 Vertical BNC Post Digikey A24513 J2 Four Pin Power Header Digikey WM1626 J3 Vertical BNC Post Digikey A24513 A Four Pin Power Header Digikey WM1626 L1 1mH Inductor Digikey DN2436 12 1 mH Inductor Digikey DN2436 The potentiometer is used to adjust the resistance so that it is exactly 1 00 Ohm xiii Hum Sniffer Design The Hum sniffer is being developed over Summer and Fall 2004 by Ambert Ho and will be described here in detail upon its completion xiv Electric Field Reception The AWESOME monitor includes design for reception of an electric field signal either in addition to or instead of magnetic field signals For this a different antenna is used consisting of a dipole and a
51. h characteristic of the square shape refers to the length of a side The length characteristic of the right isosceles triangle corresponds to the height of the base which is along the ground Because it is a right isosceles triangle the triangle s height is half that of the base The antenna thus makes a 45 angle at both cornets on the ground and a 90 angle at the top mast The AWG column refers to American wire gauge a measure of the thickness of the wire used to wind the antenna lower AWG means a thicker wire Naturally the larger antennae will need thicker wire in order to keep the resistance below 1 The turns column refers to the number of times around the wire is wrapped and the last column shows the length of wire required for the antenna loop of coutse you will need to leave some extra length on each side as well to connect it to the receiver Antenna size selection should be made based the desired sensitivity analysis of data and noisiness of site The larger the antenna the more sensitive receiver wil be The sensitivity is proportional to the area of the antenna For noisier sites when only narrowband data will be useful either the 2 89 m square antenna or the 1 69 m triangular antenna will probably be sufficient and its smaller size will make it easier to set up For quieter sites or broadband sites you can use the 24 01 m square or the 17 6 m triangle For very superbly quiet sites
52. he line receiver The elimination of the external GPS clock saves substantial cost and means one less component to bring and set up at a VLF reception site Removing the external GPS receiver reduces the physical size of all the equipment and eliminates a major cost Smaller and lighter preamp box The physical size of the preamp has been shrunk considerably Formetly placed in a box with 14 x 16 base and 7 height the preamp now measures 8 x 10 base and 5 height about four times less volume Smaller lighter more stable line receiver box The line receiver as well was placed in a better box The old boxes had a 10 x 12 base and 6 height whereas the new boxes are 7 x 10 with a 5 height about half the volume The new boxes are also more stable with a two piece design rather than the older completely disassembled frame boxes Modular card design and solder less layout The AWESOME receiver was designed with ease of testing and debugging in mind The older version had modular cards in the preamplifier but the cards were connected to a backplane that required hours to wire up manually to the inputs and to a monitor and control board The older line receiver placed everything on one large circuit board with a lot of soldered connections to the box so that removal of the card for testing or debugging required cutting a dozen or so wires that had to be re soldered into place later The new receiver has modular cards for the filter
53. hese characteristics Further technical detail on different sizes and configurations to make a valid 1 1 mH antenna can be found in the Paschal report The antenna is best placed in a quiet area as far as possible from electromagnetic noise sources like power lines generators buildings Since the antenna is built from a planar loop of wire it will only capture signals propagating with a magnetic field component in the plane Thus in order to capture signals from all azimuths it is necessary to set up two antennas otthogonal to each other Generally one antenna captures the North South component of incoming signals and a second antenna captures the East West component lt is possible however to orient the two antennae in any desired configuration All the signal electronics in the preamp and line receiver are designed for two antenna channels though one can be left out if it is not needed for a particular application So this receiver is not designed to capture signals with three degrees of freedom ie like nearfield radiation E W Antenna N S Antenna Preamp North Figure 2 Two Channel Orthogonal Magnetic Loop Antenna Configuration Figure 3 illustrates the block diagram of the preamplifier The preamp should be placed as close as possible to the antenna so that small signals aren t attenuated over long cables Since the antenna is outdoors the preamplifier must be housed in a weatherproof container The pr
54. high impedence input preamplifier circuit Electric field reception is considerably more difficult due to the smaller nature of the signals picked up by reasonably sized antennas making interference a much more difficult entity to get rid of However for quiet locations the following circuitry and antenna can be used Note that if the dipole antenna is placed too close to the magnetic field antenna there will likely be coupling between the two It is recommended to either move the dipole away from the magnetic loops or place it on top The design of the electric field antenna originated in the interferometer project conducted by Joe Payne in 2002 2003 Katie Braden and Evans Paschal collaborated on the first design The version that is specified here for AWESOME was redeveloped and redesigned by Nancy El Sakkary in Summer 2005 Below you will find a parts list and schematic for the electric field reception system Testing and Set up Once the antenna is successfully set up the process of connecting the 2005 Stanford Receiver and readying it for acquisitions is as follows 1 Plug in the computer and monitor and connect the mouse and keyboard Make sure the appropriate hardware in installed including a DVD burner if necessary and the NI DAQ PCI Make sure all necessaty supporting software is installed on the computer including StanfordDAQ an appropriate DVD burning software the NI DAQ software and Matlab
55. ilm Resistot Digikey R35 20kOHm Metal Film Resistot Digikey R36 a Metal Film Resistor Digikey R37 47 Ohm Metal Film Resistor Digikey R38 2 2 kOhm Metal Film Resistor Digikey R39 d Metal Film Resistor Digikey U1 LTC1562 Filter Chip Digikey U2 LM318 Op Amp Digikey U3 LM339 Comparator Quad Digikey U4 LTC1562 Filter Chip Digikey U7 BUF634 Buffer Chip Digikey U8 LM318 Op Amp Digikey Sideboard Ref Value Description Supplier Part D1 LED Red LED Digikey MV3750 D2 LED Red LED Digikey MV3750 D3 LED Blue LED Digikey 67 1750 JA Vertical BNC Connector Digikey A24513 J2 Vertical BNC Connector Digikey A24513 R1 60 Ohm 1 Metal Film Resistot Digikey R2 270 Ohm 1 Metal Film Resistor Digikey R3 600 Ohm 1 Metal Film Resistor Digikey U2 10 Pin 0 1 Protected Header Digikey A26268 Box Assembly Parts Qty Description Supplier Part 16 Female Crimp Terminals Digikey WM1101 1 12 Pin Receptacle Digikey WM1337 1 12 Pin Box Mount Connector Digikey 97 3102A 20 27P 4 Pin Receptacle Digikey WM1333 4 Screws 6 32 0 25 1 Fuseholder Digikey F1488 1 Fuse Slow Blow 1 8W 1 60 Hz 110V EMI Filter Digikey CCM1101 ND 1 10 Pin Ribbon Cable 6 Digikey C3AAT 1006G 1 Power Switch Digikey CH755 ND 8 Box Screws Metal Enclosure for AC Power Input Home Depot 50169 00500 MMCX to N Type Connector Synergy Systems P
56. is done in software Narrowband analysis is particularly valuable when instruments in remote areas with limited ability to transmit data back to Stanford The narrowband data would look something like this amplitude shown only data taken from http www stat stanfotd edu hail exdata html Stanford VLF group 300 200 100 1 2 3 4 5 Time mins Figure 1 illustrates the basic block diagram of the receiver The 2005 receiver consists of three main components First an antenna to create electrical signals from electromagnetic field disturbances Second is a preamplifier to amplify the signal without introducing much noise and driving the signal over a long cable The cable runs to a line receiver which filters and processes the data so it can be recorded In addition the line receiver synchronizes the data with a GPS timing signal and passes those to a PC with running software that records the signal and times 10 ImH Antenna Line Receiver t GPS Receiver Figure 1 2004 VLF Receiver Block Diagram The antenna used is a magnetic loop made by wrapping wire in a circle so that magnetic field changes create small currents in the antenna The antenna can be made arbitrarily large or small larger antennas will be more sensitive the only restriction on the antenna is that the resistance of the wire loop be 1 Q and the inductance be 1 mH as the electronics are designed for t
57. istor Digikey K R42 10 kOhm Metal Film Resistor Digikey R43 10 kOhm Metal Film Resistor Digikey R44 100 Ohm Metal Film Resistor Digikey R45 100 Ohm Metal Film Resistor Digikey R46 S 1 Metal Film Resistor Digikey K 2 21 2 R47 Ohm Metal Film Resistor Digikey K 6 34 du R48 Ohm Yo Metal Film Resistor Digikey K 6 34 is R49 Ohm Metal Film Resistor Digikey K R50 10 kOhm Metal Film Resistor Digikey R51 5 kOhm Potentiometer Digikey T1 Custom Made Transformer Whistler Radio Turn Ratio 24 548 1 Test Point Digikey 2 Test Point Digikey TP3 Test Point Digikey TP4 Test Point Digikey U1 TLO71A Op Amp 8 Pin DIP Digikey 296 7185 5 ND U2 TLO71A Op Amp 8 Pin DIP Digikey 296 7185 5 ND U3 TLO71A Op Amp 8 Pin DIP Digikey 296 7185 5 ND 04 TLO71A Op Amp 8 Pin DIP Digikey 296 7185 5 ND U6 Voltage Regulator LM317 TO 220 Digikey U7 Voltage Regulator LM337 TO 220 Digikey LM337TFS ND U8 Switch AGD442 16 Pin DIP Digikey U11 PIC12F629 Microprocessor 8 Pin DIP Whistler Radio Custom U12 8 192 MHz Oscillator Digikey U13 Voltage Regulator uA7805 TO 220 Digikey ge Regu gloj Box Assembly Parts Qty Description Supplier Part 20 Female Crimp Terminals qty 20 Digikey WM1101 1 12 Pin Receptacle Digikey WM1337 1 12 Pin Box Mount Connector Digikey 97 3102A 20 27P 2 4 Pin Receptacle Digikey WM1333 2 3 Pin Box Mount Connector Digikey 97 3102A 10SL 3P 4 Screws 10 32 0 25
58. lm Resistor Digikey K 267 o 27 R16 Ohm o Metal Film Resistor Digikey K 232 o R17 Ohm 1 Metal Film Resistor Digikey K 232 R18 Ohm Metal Film Resistor Digikey K 21 5 a R19 Oka 1 Metal Film Resistor Digikey K 27 4 P R20 Ohm o Metal Film Resistor Digikey K 27 4 Y R21 Ohm 1 Metal Film Resistor Digikey K 267 22 Ohm 1 Metal Film Resistor Digikey K R23 10 kOHm 1 Metal Film Resistor Digikey R24 k 1 Metal Film Resistor Digikey 4 12 25 R25 kOhm 1 Metal Film Resistor Digikey 26 7 a R26 kOhm 1 Metal Film Resistor Digikey R27 Open Open Circuit Do Not Populate Digikey R28 28 7 Metal Film Resistor Digikey kOhm 6 81 R29 kOhm 1 Metal Film Resistor Digikey R30 2 kOhm 1 Metal Film Resistor Digikey R31 10 kOhm 1 Metal Film Resistor Digikey R32 deat 1 Metal Film Resistor Digikey K R33 100 Ohm 1 Metal Film Resistor Digikey R34 nn 1 Metal Film Resistor Digikey K R35 nn 1 Metal Film Resistor Digikey K R36 nn 1 Metal Film Resistor Digikey K R37 1 Metal Film Resistor Digikey K R38 243 Ohm 1 Metal Film Resistor Digikey R39 1 Film Resistor Digikey K R40 243 Ohm 1 Metal Film Resistor Digikey R41 e Metal Film Res
59. ltimeter check the voltage between 15 pin and the Gnd pin and do the same for the 15V pin and the Gnd pin If they are right go to step 3 Check the voltage across the output of the HAD15 power supply If they are correct then the wiring from the power supply to the 4 pin connector may be loose or bad so repair it There may be a short in the circuit Using a multimeter check the resistance between the 15V on the motherboard side of the power connector and the ground and then repeat for the resistance between 15V and the ground pin If either is close to zero there is a short somewhere on the circuit between those voltages Please skip ahead for instructions how to repair that PROBLEM When the software opens the GPS time location data is empty SOLUTION 1 2 Make sure the serial cable is firmly plugged in at both the line receiver and the preamp PROBLEM The mouse is jumping all over the screen DIAGNOSIS The computer crashed and rebooted and during its boot up process Windows thought the GPS data on the serial port was a mouse SOLUTION Turn off line receiver reboot computer and turn on the line receiver again only after the computer has finished rebooting Stanford NS Antenna PROBLEM The data looks like this on both channels note the light band at 40 kHz may Frequency kHz not be there but the key characteristic is the fact that it s mostly blue and there ate short vertical pulses on
60. n that the software is installed on Installation Date should be the date that the hardware was installed on the computer Latitude Longitude Software Version GPS Date GPS Time GPS Quality will be filled in by the software If a Motorola GPS system is hooked up quality is simply the number of satellites the antenna sees We require at least 3 satellites for a lock to be enabled in the Motorola system In the truetime GPS is hooked up quality says LOCKED when a GPS lock is acquired STATUS INDICATORS Upon start the software looks for GPS lock During this time no acquisitions may occur If a GPS lock cannot be found within a certain time the software will start its acquisition schedule without GPS lock At the top of the GUI there are several fields that display the status of the software These include the station name installation date GPS latitude GPS longitude GPS date GPS time and GPS quality In the area entitled Next Acquisition the start and end time of the next acquisition is displayed Below there is a progress bar which fills up as the acquisition is completed Below the progress bat the general status of the software is displayed Any errors are also displayed in this area as well PASSWORD passwotd is required to enable any buttons on the software This is to prevent unauthorized changes to the software settings SAVE Any changes that are made to the software settings must be followed by a
61. ned off while data 1s being acquired REMOTE INSTALL PROCEEDURE HAIL Software required The existing HAIL Software Demodulator exe has the ability to send software updates through the internet via the Communicator program We will use the existing Demodulator exe software located in C HAILSoftware to remotely install the software Instead of updating HAILSoftware we will use a custom made DownloadNewSoftwareNext bat to install the new VLF_DAQ software We will call the computer we would like the software installed on the remote computer We will call the computer that we are installing from usually located at Stanford the server computer In general server computer will be the hail stanford edu computer in 201 1 Make sure Spysweeper is disabled on the remote computer 2 In C HAILSoftware hftp cfg of the remote computer edit the variables in hftp cfg file to the ftp settings on the server computer In general the variables should already be assigned correctly 3 In CA HAILSoftwarel Listener ini of the remote computer edit the IP address and the port number to the IP address of the server computer and the port number that the Communicator exe software is listening to Again this probably does not to be changed 4 la the server computer make sure that the computer contains the correct DownloadNewSoftwareNext bat file The correct batch file can be found in the software package under the manuals an
62. ntenna which is rated for outdoor use Model VIC 100 Connector Type N type Mounting Option Pipe clamp Cable Type LMR 400 up to 150 feet GPS Operation The GPS card communicates through the Line Receiver via standard RS 232 serial communication It uses Motorola Binary format which always starts with the sequence and ends with lt CR gt LF gt characters The format is 8 bit payload no parity and 1 stop bit Please refer to the Motorola documentation for more details The main command used for the HAIL system is the ASCII Position Information message To enable 1 pps output of information Eq lt 01 gt 5 lt CR gt lt LF gt To poll then disable 1 pps output Eq lt 00 gt 4 lt CR gt lt LF gt Cable Delay Compensation for cable delay between the antenna and the GPS card can be configured Please use the provided GPS Console application to configure cable delay and test the GPS card Cable length should be set to the GPS antenna cable length Notes Once activated the 1 pps information continually outputs information until power is removed or it is disabled with the appropriate command The Motorola GPS card has a battery on it which allows it to retain its settings for several days If the unit is not outputting data please use the GPS Console application to ensure that the GPS card is outputting data If the computer is rebooted or turned on while the Line Receiver is on and the software has
63. ock nut 6 attach guy wires and antenna to mast wire eyebolt 5 16 18 2 shank 10 fix eyebolts to mast 18 8 SS hex nut 5 16 18 10 spring lock washer 5 16 10 attach guy wires to turnbuckle tighten guy wires quick clip guy wires to mast eyebolts guy wires crimp loops in guy wires form loops at ends of guy wires stake antenna loops and guy wires into gnd jaw 5 16 left hand thread galvanized turnbuckle 5 16 31685 spring snap vinyl coated steel rope 2x20ft 2x15 ft oval compression sleeves light duty wire rope thimble concrete form board stakes with holes xii Dummy Loop The 2005 Receiver includes a design for a dummy loop The dummy loop places external signals like that from a function generator across an impedance that is equivalent to the antenna s Itis thus possible to inject signals into the input of the preamp for testing and characterization Aside from testing and calibration however a dummy loop is not needed for operation of the 2005 VLE receiver The dummy loop functions by splitting the input signal across two series resistors one large usually 10 and one small 1 2 of the antenna The smaller corresponds to the antenna impedence So to figure out the signal that is placed at the input apply simple voltage divider rules If you input a 100 mV signal split between 1 2 and 10 kQ then the signal applied across the input will be 0 1 1 1 10000 10 uV The following pa
64. odify Filter Settings GUI 19 Click OK on the Data Processing GUI 20 Click on the Broadband Settines button a Click on Add in the Select Broadband Channel section b Click save data to hard drive c Select 100kHz for sample frequency d Select BB12500 for primary filter e Select ADC1 for A D card f Select 1 for A D channel number g Click on Add in the Set Acquisition Timing section h Select Continuous radio button i Enter 03 30 00 for Start p Enter 03 00 00 for End k Enter 00 30 00 for Period 1 Enter 00 30 00 for Duration m Click on Add in the Select Broadband Channel section n Click save data to hard drive o Select 100kHz for sample frequency p Select BB12500 for primary filter q Select ADC1 for A D card t Select 2 for A D channel number s Click on Add in the Set Acquisition Timing section t Select Continuous radio button u Enter 03 30 00 for Start v Enter 03 00 00 for End w Enter 00 30 00 for Period x Enter 00 30 00 for Duration y Click cquisition Settings Heal Time Processing Send full bandwidth raw uoj I Delete Perform FFT 1 Previous i 3 m setting Previous Use this channel s timing for all channels 21 Click OK for Broadband Settings GUI 22 Click on the Narrowband Settings button Narrowband Acquisition Set
65. ote computer from the server computer In order to have access to the remote computer we must specify settings on the controlling computer In particular we need the IP address and port number of the server computer The remote computer will then establish a connection with the server computer The server computer controls the remote computer via the Communicator software We can for example get the status of the remote computer view and change the settings of the remote computer restart the remote computer and command the remote computer to FTP select data We can also update the software of the remote computer When we want to view the software settings of the remote computer the remote computer sends the software settings to the server computer via FTP For this reason a user name and password of the server s is required We may have multiple server computers controlling remote computer In this case we simply click the add button to add the information for more server computers Real Time Communications Settings Connection index number o OK Unique connection name Cancel IP address Port number 0 User name Password Previous Newt Delete DATA PROCESSING The data processing GUI contains sub GUIs that are pertinent to the signal processing that is done on the raw data after it has been acquired Data Processing Create Modify Filter Settings DK FFT Settings Cancel Superpased Epoch CREAT
66. quencies in the ELF VLF range which is roughly 30 Hz 50 kHz By studying the data recorded from the antenna a wide range of atmospheric effects can be understood because they create disturbances in the typical magnetic field A wide variety of phenomenon can be studied with ELF VLF receivers including but not limited to lightning discharges radio atmospherics whistlers lightning induced electron precipitation LEP cosmic gamma ray flares terrestrial gamma ray flashes IGFs sprites and other optical discharges one hop and two hop magnetospheric echo ground ionosphere coupling solar flares geomagnetic storms and more As such the VLF group has been building and using VLF receivers for decades refining the design over the years The receivers have reached the point of sensitivity where nearly any signal above the ambient Earth noise floor can be detected For example it will pick up the miniscule signal from a digital watch in the vicinity This is important because some of the observed disturbances in the electromagnetic field are very small In spring 2003 Justin Tan and Morris Cohen began building the newest incarnation and it was completed in fall 2004 A prototype line receiver modeled almost exactly off of an older version was completed in June 2003 Full development began in autumn 2004 and was assembled in spring 2004 Initial field testing and final changes were made during summer 2004 A number of deployments occurred
67. r Digikey R20 410 Ohm Metal Film Resistor Digikey R21 350 Ohm 1 Metal Film Resistor Digikey T1 70 7 Line Audio Transformer Stancor A 8096 T2 70 7 Line Audio Transformer Stancor A 8096 1 Test Point Digikey U1 Voltage Regulator uA7805 220 Digikey 296 13996 5 ND U2 Voltage Regulator uA7905 220 Digikey LM7905CTNS ND U3 4 Pin Power Header Digikey WM1626 U4 Inverters 74ACT04 Digikey U5 RS232 Chip Max3323 DIP Maxim MAX2232 U6 10 Bit D A Converter THS5651 SOIC Digikey 296 2992 5 ND U7 10 Pin 0 1 Protected Header Digikey A26268 U8 9 Pin Serial Connector Digikey 309M U9 44 Pin PLCC Socket Digikey AE7328 U10 10 MHz Oscillator DIP Vectron VTA1 1B1 10M000 U11 Inverters 74HC04 Digikey 296 12772 5 ND U12 10 Pin 0 05 Header Samtec SEMC 105 01 S D U13 Voltage Regulator LM317 220 Digikey LM317HVT ND U14 Voltage Regulator LM317 TO 220 Digikey _ U9 Altera 7000 7064 Arrow EPM7064AELC44 7 U12 Motorola GPS 12 Timer Card Synergy Systems LTC1562 Filter Card Ref Value Description Supplier Part C1 10 pF Ceramic Capacitor Digikey C2 0 1 uF Ceramic Capacitor Digikey C3 1 0 uF Tantalum Capacitor Digikey C4 0 1 uF Ceramic Capacitor Digikey C5 1 0 uF Tantalum Capacitor Digikey C6 4 7 uF Ceramic Capacitor Digikey C7 47 pF Ceramic Capacito
68. r Digikey C8 0 1 uF Ceramic Capacitor Digikey C9 1 0 uF Tantalum Capacitor Digikey C10 0 1 uF Ceramic Capacitor Digikey C11 1 0 uF Tantalum Capacitor Digikey C12 39 pF Ceramic Capacitor Digikey C13 27 pF Ceramic Capacitor Digikey C14 390 pF Ceramic Capacitor Digikey C15 0 1 uF Ceramic Capacitor Digikey C16 1 0 uF Tantalum Capacitor Digikey C17 0 1 uF Ceramic Capacitor Digikey C18 1 0 uF Tantalum Capacitor Digikey C19 33 pF Ceramic Capacitor Digikey C20 0 1 uF Ceramic Capacitor Digikey C21 1 0 uF Tantalum Capacitor Digikey C22 0 1 uF Ceramic Capacitor Digikey C23 1 0 uF Tantalum Capacitor Digikey C24 8 2 pF Ceramic Capacitor Digikey C25 15 pF Ceramic Capacitor Digikey C26 0 1 uF Ceramic Capacitor Digikey C27 0 uF Tantalum Capacitor Digikey C28 0 1 uF Ceramic Capacitor Digikey C29 0 uF Tantalum Capacitor Digikey C30 0 1 uF Ceramic Capacitor Digikey C31 0 uF Tantalum Capacitor Digikey C32 0 1 uF Ceramic Capacitor Digikey C33 0 uF Tantalum Capacitor Digikey D1 1N4005 Multiplexer SOIC 20 Digikey D2 1N4005 Multiplexer SOIC 20 Digikey D3 1N4005 4082 Digikey D4 1N4005 Multiplexer SOIC 20 Digikey R1 20 kOhm Metal Film Resistor Digikey R2 k A Metal Film Resistor Digikey R3 10 kOhm Metal Film Resistor Digikey R4 k zu Metal Film Resistor Digikey R5 75 kOhm Metal Film Resistor Digikey
69. r some other insulating material The two contacts that connect to the external HAD power supply should be especially well covered and protected since unlike the rest they are not behind a metal box IT IS HIGHLY RECOMMENDED THAT YOU AVOID TOUCHING ANYTHING WITHIN THE VLF RECEIVER WHILE THE POWER PLUG IS INSERTED The AuxB switch was accidentally shorted so one of the power lines so it will not work AuxA is not typically needed so this is not a major issue but in order to use AuxB you will have to follow these instructions The polarities of the line transformers on the output of the preamplifier and the input of the line receiver are not properly labeled Please use the following orientation when you placing the line transformers trace on the filter card must be cut and the two ends connected with 4 7uF ceramic capacitor Please refer to the following diagram 1 Acknowledgements Justin Tan and Morris Cohen the chief creators of the 2005 Stanford receiver would like to thank the following people for the help and contributions to this long but rewarding process Professor Umran Inan for providing guidance throughout the process and maintaining a high standard Phil and Debbie Scherrer for providing the spark to redesign the system and finding great uses for them Shaolan Min for processing PO after PO after PO after PO and still putting on a smile Dr Evans Paschal for endlessly h
70. ramic Capacitor Digikey 399 2054 ND C8 10 pF Ceramic Capacitor Digikey 399 1888 ND C9 10 pF Ceramic Capacitor Digikey 399 1888 ND C10 22 uF Tantalum Capacitor Digikey 399 1531 ND C11 0 47 uF Tantalum Capacitor Digikey 399 1443 ND C12 10 nF Polyprolylene Capacitor Digikey C13 3 3 nF Ceramic Capacitor Digikey 399 2001 ND C14 3 3 nF Ceramic Capacitor Digikey 399 2001 ND C15 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C16 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C17 3 3 nF Ceramic Capacitor Digikey 399 2001 ND C18 3 3 nF Ceramic Capacitor Digikey 399 2001 ND C19 4 7 uF Ceramic Capacitor Digikey 399 1302 ND C20 27 pF Ceramic Capacitor Digikey 399 1891 ND C21 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C22 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C23 4 7 uF Ceramic Capacitor Digikey 399 1302 ND C24 1 0 uF Tantalum Capacitor Digikey C25 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C26 1 0 uF Tantalum Capacitor Digikey C27 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C28 22 uF Tantalum Capacitor Digikey 399 1531 ND C29 22 uF Tantalum Capacitor Digikey 399 1531 ND C30 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C31 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C32 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C33 10 uF Tantalum Capacitor Digikey C34 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C35 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C36 0 1 uF Ceramic Capacitor Digikey 399 2054 ND C37 0 1 uF Ceramic Capacitor Digikey 399 2054 ND D1
71. rmation over the internet ftp li Improvements to the Stanford University 2005 VLF Receiver The AWESOME monitor includes a number of modifications in electrical performance mechanical layout cost and ease of use Since some users of the AWESOME receiver may already be familiar with older design iterations it is helpful to highlight these changes and additions specifically Elimination of line driver circuit The previous receivers contained an elaborate line driver card in the preamplifier in order to drive the signal over as much as 2000 ft of cabling to the line receiver In AWESOME this whole card was eliminated and the output op amp in the preamp card was swapped with one that has more output drive ability This greatly simplifies the design of the preamplifier Elimination of 35 V preamp supply In previous designs the preamp was powered from a 35 V signal coming from the line receiver The 35 V was generated in the line receiver directly from 110V AC power Once in the preamp this 35 V single ended voltage would then be regulated into a 15 V bipolar supply The chief disadvantage was that the preamp and line receiver had different grounds ground for the preamp was at 17 5 V for the line receivet which made it impossible to probe signals in the preamplifier without shorting out the DC signals Instead the AWESOME receiver sends a direct 15 V signal from the line receiver to the preamplifier This removes the
72. s GUI do not directly affect the data acquisition It should be used as reference when studying data acquired Antenna Properties SERIAL SETTINGS Serial Port Settings These are settings that the GPS system uses to communicate to the computer through the serial port Motorola GPS system should use the following settings Baud rate 9600 Byte size 8 Buffer size 2048 Parity None Stop bits 1 Truetime GPS system should use the following settings Baud rate 9600 Byte size 7 Buffer size 2048 Parity even Stop bits 1 ADC SETTINGS Most important in the hardware information GUI is the ADC sub GUI For each ADC card installed in the computer the user should enter information of the card The Device number assigned to the ADC card can be found on the NIDAQ configuration utility ADC Information A D card number o Unique card name Ci Cancel Device number li Card SN Card type Previous Nest Add Delete COMMUNICATIONS SETTINGS The information in this GUI is important for any features in the software that make use of the Internet It is important that the Have Internet Access box is checked if internet 15 available and not checked if it is not available If this box is not checked any features requiring internet connectivity will be disabled OK Network IV Have Internet Access FTP SETTINGS We would like to FTP data particularly narrowband d
73. s of this error originates from jitter in the GPS signal which is the limiting error in this scheme The phase error at higher and lower frequencies will be scaled proportionately to 20 kHz and 2 16 i e a 10 kHz signal has a phase error of 2 16 2 1 08 The circuit was tested in two ways First the oscillator output was connected to a network analyzer which plotted the frequency content of the 10 MHz signal When the power was turned on you could visibly see the frequency start at some amount above ot below 10 MHz and then slowly over a few minutes time zoom in towatd 10 MHz exactly The plots of the steady states taken from the Network Analyzer ate shown below In a second test the FPGA was programmed to output a digital signal whenever the 10 MHz clock deviated enough to warrant adjusting the DAC Additionally the drift between the two signals could be obsetved on a fast oscilloscope and it was observed that the new 100 kpps signal drifted by less than 300 ns at any time 5 10 1 dB REF 86 1 dBm 16 069 dBm 7 3 i SELECT 5 1da 220034 kHz LETTER TENE A NM NT CHi Spectrum BACK SPACE ERASE TITLE DONE a 3 STOR DEV EN ONU PER ATTE C MPE A TEI DISK REN 1 Hz VBH 1 Hz RTNH dB SHP 5 471 sec CANCEL START 99 995 kHz STOP 188 8085 kHz True Time
74. the same result Figure 5 shows the hardware block diagram n 10 MHz 100 kHz 10 Bit D A FPGA Converter Divider Sampling Oscillator Clock FPGA Counter 1 Hz GPS Signal Figure 5 Clock Maintenance Circuit The FPGA 15 the main component here It counts cycles from the 10 MHz oscillator between every 1 Hz GPS pulse and if the number is greater or less than 10 000 000 the FPGA will change the value of the D A converter s inputs which thereby adjust the oscillator accordingly The accurate 10 MHz clock 15 divided down to 100 kHz Since the 10 MHz signal is synchronized every second as long as the count rate of the oscillator remains at 10 000 000 the frequency remains accurate within 1 Hz this the error of the sampling clock will be better than 0 1 parts per million ppm Since the error stretches over 1 s between GPS synchronizations that corresponds to 100 ns of The feedback should be able to improve further on 0 1 ppm since even fractions of a count per second error will eventually lead to clock adjustment But since 0 is already below the GES error we will stay conservative maximum skew at any time Since the GPS signal itself has a built in skew of 200 ns the total error in the sampling clock 15 300 ns or 0 3 ppm Since a 20 kHz signal propagates one degree of phase in 111 ns and the sampling clock s error is 0 3 ppm or 300 ns the phase error at 25 kHz will be 300 139 2 169 Two third
75. the time and 10 11 12 13 14 15 16 location The time quality field reflects on the number of satellites found by the GPS catd Run a test acquisition using the instructions described in the software guide Make sure that the acquisition begins and ends at the proper time and that the correct files appear in the data directory Open up the preamplifier in the silver box and check to make sure all screws ate tight no chips ot part have fallen out or come loose If they have tighten or replace them again Connect the preamplifier to the line receiver using the long Belden 1217B cable This thick four twisted pair shielded cable will transfer power from the line receiver to the preamplifier and signals from the preamp to the line receiver Turn the gain switch all the way counterclockwise on the big baseboard of the preamplifier The LED next to 30dB should be illuminated and the mode from that point can be changed by flipping the switch All modes that past 0 dB which aren t labeled are also 0 dB but keep the switch in one of those four positions Run another test acquisition and again make sure it runs as predicted Attach a dummy loop to the ends of the preamplifier the input and follow the calibration instructions outlined later in this packet Be sure to check that the preamp cards are balanced before proceeding with the calibration Replace the dummy loop connection with an antenna connection
76. tings Select Narrowband Channel Narrowband Channel Number 0 Previous Next Add Delete Channel Name Call Sign NLK Center Frequency 24800 Calibration Factor 5 v Save Data to Disk FTP Data Is MSK Modulated Do Low Res Spheric Channel V Synoptic Cleanup Data Rate and Filtering Primary Filter Number NB200 Y Secondary Filter Sample Frequency 50 Hz Heal Time Processing FET Setting Number Send Full Bandwidth Haw Cancel Superposel Epoch Setting Number FTP FTP Setting zl Selec A D Card A D Card Number AD CI A D Channel Number Set Acquisition Timing Narrowband Timing Number o Previous Next Add Delete Use this channel s timing for all channels Continuous HH MM SS Start foo foo oo Period oo fos 00 End 13 oo 0 Duration 1 0 0 C Synoptic HH MM SS a Click on Add in the Select Narrowband Channel section b Click save data to hard drive c Click FTP data d Click Is MSK Modulated e Click Synoptic Cleanup f Enter NLK under Channel Name g Enter 24800 for Center Frequency h Enter 5 for Calibration Factor 1 Select 50Hz for sample frequency j Select NB200 for primary filter k Select ADCI for A D card 1 Select 1 for A D channel number m Click on Add in the Set Acquisition Timing section
77. vert to mat FTP file starting at 23 30 Delete bin file upon successful FTP end at 3 30 Delete direotoios after 20 days Previous Next Add Delete a Enter vlf europe stanford edu under Host IP Address b Enter 21 under Host Port Number c Enter the ftp username under username d Enter the ftp password under password e Check FTP file f Enter 23 30 00 under FTP file starting at Enter 3 30 00 under end This will give 4 hours to FTP the files h Enter vlf europe for FTP name i Click OK 15 Click OK on the FTP Setting Dialogue 16 Click OK on the Communications Settings dialogue box 17 Click on Data Processing Data Processing a Click Add b Enter NB200 under Unique Filter Name c Click on Filter from File 2i xi Look n 5 tte rt bb_fitert 2500 dat My Recent Documents My Documents mr My k File name b Files ol type tara Places read only d Navigate to the Filter directory and select the file nb_filter dat Click OK to select the filter file f Click Add g Enter BB12500 under Unique Filter Name h Click on Filter from File 1 Navigate to the Filter directory and select the file bbfilter_1250 dat j Click OK to select the filter file k Click OK on the Create M
78. ware will then be installed on the remote computer under cAVLF DAQ LOCAL INSTALL PROCEEDURE HAIL Software NOT required In the case that HAILSoftware is not installed on the remote computer or the internet is not accessible in the remote computer we must install the software locally using a CD with the software on it 1 Make sure Spysweeper is disabled on the remote computer 2 Make a directory preferably NVLE DAQ where the software should be installed into This directory should not have any spaces 3 Copy the entire contents of the CD into the install directory 4 Run VLF DAQ exe The startup folder will be updated the first time the software is run Overview of the Software MAIN GUI The main GUI consists of various status indicator and buttons which open up sub GUIS 1 Stanford University LF DAQ Station Nane Installation Date Password Stanford February 21 2005 Latitude Longitude Software Version li acu sns GPS Date GPS Time GPS Quality 02 22 0 03 53 16 4 Next Acquisition Start Time End Time o fofo 1 IMI L Status Error Messages Continuing without GPS Quality Lock Data Processing Hardware Information ED DVD Writina Broadband Settinas Communicatior Setings About VLF DA Narrowband Settings Disk Management Exit Restore Settings Station Name is the name of the statio

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