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ISIS 3 INTEGRATED SEISMIC INSTRUMENTATION SYSTEM RADIO TELEMETRY SYSTEM Rev: A 01/2012 VLF DESIGNS 1621 BELLA VISTA DR JACKSON,MO. 63755 573-204-1286 [email protected] 1 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. TABLE OF CONTENTS ISIS 3 OVERVIEW 3 ISIS 3 SPECIFICATIONS 4 FUNCTIONAL BLOCK DESCRIPTIONS RECEIVER 5 OUTPUT MULTIPLEXER 5-8 TRANSMITTER 9 CANISTER 10 OUTPUT TEST CABLE 10 ADJUSTMENTS TRANSMITTER 11 RECEIVER 11-12 OUTPUT MULTIPLEXER 12-13 3 CARRIER OUTPUT MUX LEVEL SPREADSHEET 14 6 CARRIER OUTPUT MUX LEVEL SPREADSHEET 15 APPENDIX A HAMTRONICS RECEIVER DOCUMENTATION 16-22 APPENDIX B HAMTRONICS TRANSMITTER DOCUMENTATION 23-30 APPENDIX C PARTS LISTS 31 RADIO CANISTER 32-35 OUTPUT MULTIPLEXER 36-38 2 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. ISIS 3 OVERVIEW The ISIS 3 radio telemetry hardware represents the first major redesign of the field hardware for analog NBFM telemetry. The new RF telemetry equipment utilizes modified Hamtronics radio equipment for receiving and transmitting the data from the various short period monitoring sites. All capacitors used in the circuitry are either mylar, ceramic or high temperature electrolytic in order to maximize longevity of the circuitry. All pc board connections utilize gold plated connectors to prevent interconnection problems due to oxidation. The radio transmitters are modified to remove their pre-emphasis networks. An external switching type high efficiency power supply provides power to the driver and final so that the power output of the radio can be controlled. The radio receivers are modified for low distortion in order to prevent intermodulation between carriers. The receiver outputs are run through external bandwidth limiting filters prior to multiplexing to minimize the accumulation of noise in the multiplexed signal. All power, output signal and monitoring connections are made via a single round shielded 10 conductor ribbon cable. Three preamplifier output signals, gain range signal, analog ground, VCO carrier signals, received audio and composite transmit audio are made available external to the canister for onsite system diagnostics. Transient suppression on the power leads protects the radio and multiplexer equipment. The entire package is housed in a shielded polished stainless steel cylinder capped with aluminum plugs and “o” ring seals for shielded watertight operation to a depth of 25 ft. The system has been designed to fit into the top of a 4” thin wall PVC pipe borehole. In addition a 4” PVC screw plug has been installed on all leads coming from the radio canister, in order to seal the borehole containing the radios and sensors. 3 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. ISIS 3 RADIO SYSTEM SPECIFICATIONS RADIO TRANSMITTER Operating voltage: 12-14 VDC Operating current: Approximately 70mA @100mW 90mA @200mW 110mA @300mW 130mA @400mW 150mA @500mW 200mA @750mW 250mA @1000mW Output Power: 100mW to approximately 1W Frequency Range: 216-220 Mhz, 5 Khz channel spacing Frequency Stability: ±2ppm (-30˚C to +60˚C) Output Protection: short or open Output Impedance: 50Ω Spurious Outputs: -65 dB below carrier or better Modulation Bandwidth: 300 – 3500 Hz Modulation Linearity: 0.1% or better Input Impedance: 1KΩ Deviation Sensitivity: ±5Khz for 1V r.m.s. (2.83Vp-p) Radio Receiver Operating voltage: 12-14 VDC Operating current: Approximately 40mA. Operating Frequency: Factory programmable with 2 alternate frequencies Channel Spacing: 5 Khz Sensitivity: 0.25uV or better (12dB SINAD) Audio Bandwidth: 300-3000Hz Output Impedance: 8 Ω Audio Output: 1Vr.m.s. for ± 5 KHz Deviation Normal Modulation Bandwidth: ±5 KHz Modulation Acceptance: ±10 KHz Distortion: Less than 1.0% THD Selectivity: 1st IF, 2 pole, 250Khz, 2nd IF, 6 pole, 30Khz Image Rejection: 70dB or better Frequency Stability: ±2ppm (-30˚C to +60˚C) Output Multiplexer Card Transmitter Variable Power Supply: 3-11 VDC Output Multiplexer: 3 channel, individual adjustable weighting, adjustable output to 1Vrms. Output Impedance: 100 Ω 4 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. Receiver Filter 1: 1.9KHz Low Pass, 7 pole, (For Low Group Frequencies) Receiver Filter 2: 3.4Khz High Pass, 4 pole, 4.5KHz low pass 3 Pole(For High Group Frequencies) Functional Block Descriptions Radio Receiver The radio receiver used in the ISIS 3 system is purchased from Hamtronics and modified to provide proper operation when used with data telemetry equipment. The modifications consist of removing very narrow band IF filters and replacing them with broader band filters. Receiver de-emphasis components are also removed because the companion transmitters do not employ preemphasis. The quadrature discriminator is also modified for wider bandwidth and lower distortion. Additional modifications to the receivers internal low pass filter are required when use of the three highest frequency carriers are anticipated. Operating power for the radio receiver (s) is provided by the output multiplexer card through an RF filter network from the power input. A single stage of transient suppression is provided by the output multiplexer card. The radio output signal and the filtered radio output signal are available at test points on the output multiplexer card. The radio outputs are set to 1Vrms (2.828 Vp-p) output for a single 1 KHz carrier deviation of ± 5 KHz during radio calibration. Output Multiplexer Board The output multiplexer board is made in three different versions. A transmitter only version for outer ring ( low or high group carriers) stations; a repeater version for multiplexing an inner (middle group carriers) and outer ring station (low group carriers) and 5 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. a non-standard repeater version for multiplexing two receivers (low and high group carriers) with an inner group station. A schematic is provided for a completely loaded system. Unused filter components are deleted from the other versions to save power and minimize cost. Low Group Receiver Filter If the ISIS-3 hardware is ordered with a single receiver, (for a repeater site), it is assumed that this receiver will provide a signal containing the lowest three frequency carriers for subsequent multiplexing with the three middle carrier frequencies. (A high carrier group multiplexed with a middle carrier group requires that the received signal be processed through a high group receiver filter, and this type of repeater will not contain a low group filter.) The receiver output signal (TP601) is routed through a bandwidth limiting filter prior to multiplexing with locally generated carriers to minimize the accumulation of received radio background noise. A 7th order low pass filter is provided to limit the bandwidth of the received signal to only that required by the carriers received. The high frequency corner of this filter is set at 1.9KHz. A 0.5dB Chebyshev filter is used to maximize out of band roll-off consistent with minimal group delay distortion and flat response for in band signals. Each filter provides 0 dB of gain within the pass band. A trimpot at the filter output (TP602) allows variable attenuation of the signal prior to multiplexing. This filtered and possibly attenuated radio output signal is also available for analysis on a test jack on the ISIS 3 test box. High Group Receiver Filter If the ISIS-3 hardware is ordered with two receivers, (for a non-standard repeater site), it is assumed that the first receiver will provide a signal containing the lowest three frequency carriers for subsequent multiplexing with the three middle carrier frequencies. The second receiver will provide the highest three carriers for subsequent multiplexing. Both receiver output signals are routed through bandwidth limiting filters prior to multiplexing with locally generated carriers to minimize the accumulation of received radio background noise in the composite signal. The low group signal will be connected to a low group filter as previously stated. The high group (TP603) signal is processed differently. A combination of low and high pass filters are utilized to band limit noise from the receiver. The high pass filter is a 4 th order filter at 3.4 KHz 6 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. and the low pass filter is a third order filter at 4.8 Khz. These filters also have a 0.5 dB Chebyshev response. This filter provides 0 dB of gain within the pass band. A trimpot at the filter output allows variable attenuation of the signal (TP604) prior to multiplexing. The filtered and possibly attenuated radio output signal is also available for analysis on a test jack on the ISIS 3 test box. Output Multiplexer The output multiplexer combines by means of FDM the internally generated carriers from the site with up to two signals from different receivers. The output of this multiplexer is the composite modulation signal for the transmitter. The locally generated signals from the ISIS 3 sensor package are brought into the multiplexer through transformer T601, and then variable attenuation is provide to this signal by trimpot R626. The output of this trimpot can be seen on the grey test point TP 605. The multiplexer composite output signal is available on the white test point TP606 and on a test jack on the ISIS 3 test box. The gain of the multiplexer can be set from 0.3 to 1.3 by trimpot R632 and provides a means of adjusting the overall composite signal level that will modulate the transmitter. 7 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. 8 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. Transmitter The radio transmitters used in the ISIS 3 system are purchased from Hamtronics and subsequently modified to provide proper operation when used with data telemetry equipment. The modifications consist of removing the de-emphasis components and the application of a variable voltage to power the final stage. An additional modification supplies 12V power to the pre-driver and driver stages. Additional modifications to the transmitters internal low pass filter are required when use of the three highest frequency carriers are anticipated. Operating power for the radio transmitter is provided by the output multiplexer card directly from the fused power input. A single stage of transient suppression is provided by the output multiplexer card. Power for the final is obtained from a switching regulator configured around U604. The output of this regulator is between Vin-3.1 and 2VDC. Higher radio output powers (at the expense of power regulation) may be obtained by removing the wht/org wire from J604-1 and connecting it to J604-4. The transmitter may be completely powered down by unplugging P604 from J604 in order to check for possible receiver desense in repeater configurations. The transmitter deviation sensitivity is set to 1Vrms (2.828 Vp-p) output for a single carrier deviation of ± 5 KHz during radio calibration. 9 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. NOTE: Blue wire attachment point changed after photo was taken. Photo indicates variable power to driver and final, not just final. 10 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. Radio Canister The radios and multiplexer card are housed in a 4” diameter stainless steel cylinder with aluminum end caps. This results in a totally shielded enclosure to minimize leakage of any internally generated signals other than those on the transmitter cable. O-ring seals, screw seals and cord seals are used to make the entire assembly waterproof to a depth of 25 ft. The o-rings should be cleaned and re-greased any time the container is opened for service or adjustment. The canister requires 6 small bags of desiccant and they should also be replaced any time the equipment requires service. The cable seals are installed on the inside of the enclosure to minimize corrosion between the brass and aluminum. An epoxy seal is poured on the outside as a secondary seal between the wires and the enclosure. The canister may be opened by removing the seal screw from the bottom end of the package. Remove the bottom cap and unplug the 8 position cable plug from the header on the multiplexer PC board. The internal assemblies may then be removed by gently pushing up on the end of the aluminum plate that contains the clip nut until the upper O-ring clears the top of the cylinder. Output Test Cable A ten position round, shielded, ribbon cable connected to J605 on the output multiplexer card carries the test and diagnostic signals from the ISIS 3 system to the external test box. A separate ground lug has been provided for the cable shield connection. 11 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. Adjustments Receiver Adjustment Full instructions for receiver adjustment and troubleshooting can be found in Appendix A which contains the Hamtronics documentation. In general, the receiver is adjusted like any other NBFM receiver. The following is a short form of receiver adjustment. The receiver can operate at one of three frequencies, the primary (as indicated on the label) and 2 alternate frequencies that are selectable by jumper and given in the attached calibration sheet. If a new frequency is selected, the VCO coil, L1 must be set to center the range of the phase comparator error signal at approximately 2VDC at TP1. Set the squelch adjustment on the receiver (R25) fully CCW. A low level signal with 1 KHz modulating frequency and a deviation of ±5 Khz is injected into the input such that a SINAD reading of approximately -12 dB is obtained. The input stages are then re-tuned for maximum sensitivity. The input signal may be reduced further as needed during the alignment process. Once maximum sensitivity is attained the input signal is adjusted for a SINAD reading of exactly -12 dB. The rf output level from the test source at this point is equal to the sensitivity of the receiver which should be in the range of .15 to .25µV. NOTE: because of the wide band nature of the modified 1st IF filter, T1 and T2 tune extremely broadly, and normally do not measurably affect the response of the receiver. Set the signal generator to produce -80dBm signal with the modulation unchanged. Connect a distortion analyzer to the receiver filter output on the output multiplexer card. Retune the quadrature coil T3 for minimum distortion. If 1% or less distortion cannot be attained, It is usually necessary to adjust the TCXO U3 slightly, and then retune the quadrature coil. Repeat as needed to minimize distortion. Finally, set the receiver output level to 1 Vrms at the receiver input TP on the output multiplexer board using volume control R37 on the Hamtronics receiver board. If receiver squelch is to be used with the receiver, set the RF signal generator to produce a fully modulated 1 KHz signal at the desired RF squelch level. Set squelch adjustment R25 fully CW. The receiver should now be squelched. (If not, select a lower RF squelch level). Slowly turn squelch adjustment R25 CCW until the receiver output squelches. Increase the RF signal generator output and verify that the receiver unsquelches. Transmitter Full instructions for transmitter adjustment and troubleshooting can be found in Appendix B which contains the Hamtronics documentation. In general, the transmitter is adjusted like any other NBFM transmitter. The following is a short form of transmitter adjustment. The transmitter is completely frequency agile within its band. Once a new frequency is selected, the VCO coil L1 must be set to center the range of the phase comparator error correction signal, to approximately 2VDC at TP1. 12 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. R632 (power adjustment) on the output multiplexer board should be set fully CCW. The RF circuits of the transmitter are then adjusted for maximum power output. Once all adjustments are complete, final power output adjustment should be made by adjusting R632 CW to decrease radio output power until the desired power output is obtained. L5, L8 and C44 may be slightly retuned to increase the power output at this level and then R632 adjusted further CW to return to the desired power output. This will maximize the efficiency of the final at the desired output power level. Finally, the deviation adjustment R35 is set fully CW. Adjust af gain pot R26 so that a 1 KHz, 1 Vrms signal provides ± 5 KHz of deviation. This will also automatically set the limiter. Transmitter Multiplexer Adjustment Adjustment of the multiplexer is slightly complicated by the fact that one of the carriers has AM modulation applied to it to convey the gain range information. The increase in amplitude of this one carrier must be accounted for in order to avoid limiting in the transmitter and distortion in the radio system that would increase during gain range events. Adjustment can be done with either an oscilloscope (p-p signal) or true rms voltmeter. Once the VCO carriers are stabilized, the oscilloscope method can be difficult to implement because the carriers are phase locked and harmonically related to one another. This relationship may tend to obscure the peaks of the waveform during the measurement interval. The rms method does not suffer from this drawback. In any case, the positive or negative peak of the modulation signal cannot exceed 1.414Vp, or peak limiting in the transmitter will occur leading to serious distortion. In reality, we will only use 95% (1.343Vp) of the available 5KHz (4.75 KHz) deviation so that a small safety factor is built in to the system. A math cad spread sheet is supplied indicating how the modulation voltage values were calculated. Outer Ring Site, (non repeater) In this case there are only three carriers involved. Set the local level trimpot, R626, fully CW. Each locally generated VCO carrier is normally 1Vp-p in amplitude and the input multiplexer will add them together to create an approximately 3Vp-p, (866mVrms), signal at test point TP605. The actual modulation voltage will be set using the composite gain adjustment, R632. Using the values determined from the spreadsheet, set R632 to produce a voltage of 411 mVrms, (2.015Vp-p), at test point TP606. Then shake the sensor stack; the voltage at TP606 should increase to 582 mVrms. Careful observation of this waveform will indicate a voltage of 2.687 Vp-p. This is all that is required to properly set the transmitter modulation. Note that the modulation meters in most service monitors are average reading devices and thus will indicate significantly less than the 4.75 Khz peak deviation expected. 13 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. Inner Ring Site, (repeater single receiver) In this case, the three locally generated carriers are multiplexed with three remote site carriers from the radio receiver. The same concerns about limiting in the transmitter are addressed. In the first step, the local carriers are slightly attenuated to keep from overdriving the output multiplexer. Adjust the local level adjustment R626 to produce a 250 mVrms signal at test point TP605. (Make sure that the gain range circuit is not activated during this adjustment!) In the next adjustment, the received VCO carriers will be equalized to the locally generated VCO carriers. Adjust the low group level trimpot , R609 to produce 250 mVrms at test point TP602. (Make sure that the gain range circuit is not activated during this adjustment!) The absolute values of the previous two adjustments are not critical, but both levels should be equal, so that the remotely generated carriers are equal in amplitude to the locally generated carriers in the composite signal applied to the transmitter. Finally, adjust output level trimpot, R632, to produce a signal of 291 mVrms at test point TP606. (Make sure that none of the gain range circuits are activated during this adjustment!) This signal amplitude will insure that when both ISIS 3 systems are operating in gain ranging mode, the transmitter will not be over modulated. The modulation voltage will increase to 411 mVrms when both systems are in gain ranging mode. This is all that is required to properly set the transmitter modulation in this case. Note that the modulation meters in most service monitors are average reading devices and thus will indicate significantly less than the 4.75 Khz peak deviation expected. 14 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. 15 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. 16 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email. 17 Copyright disclaimer: This manual may be copied in full or in part by the equipment owner or user without written permission from the manufacturer. VLF Designs retains the right to make improvements or changes in the equipment design as needed. If any additional information is required by the equipment user, please contact VLF Designs by phone or email.