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7/27/2019 Calibration of Monitoring Antennas and Instruments
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Calibration of monitoringantennas and instruments
Mr.Song KepingEngineer of Management of station and network Division
State Radio Monitoring Center
[email protected]+8610-68318264
Radio Monitoring and Spectrum Management Training
(China,23-31,May,2005)
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General considerations
Calibration of frequency
Calibration of measuring ormonitoring receivers
Calibration of the measuring
antennasCalibration of fixed monitoringrecording instruments
Calibration of monitoringantennas and instruments
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General considerations
General considerations
Calibration of frequency
Calibration of measuring ormonitoring receivers
Calibration of the measuring
antennasCalibration of fixed monitoringrecording instruments
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Calibration:
-Ensure the accuracy of the technical parameters
-Ensure the value is within the specified uncertainty
Technical parameters of the equipment
-Change over time
-Influenced by many factors
General considerations
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Regular calibration of the equipment
-Decrease the risk of error
-Find the equipment need to be repaired
-Traces the technical parameters to standards
Parameters most frequently calibrated
-Frequency
-Signal level
-Antenna gain
-Values of legal significance
General considerations
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Calibration documents
-Accompany with equipment
-Calibration report
-Indicate calibration status
-Incorporated in the equipment file
Calibration interval
-No generally applicable period
-Be chosen from a technical viewpoint
General considerations
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High expense of calibration
-Because of the high demand of equipment used
-Make calibration in monitoring station more difficult
Calibration can be provided
-By service and support centers of manufacturer
-By external calibration lab
General considerations
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Calibration of frequency
General considerations
Calibration of frequency
Calibration of measuring ormonitoring receivers
Calibration of the measuring
antennasCalibration of fixed monitoringrecording instruments
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Calibration of frequency
-Check the accuracy of crystal oscillator
-Correct the error
Calibration task in monitoring station
-Exactly know the uncertainty of equipment
-Find the equipment need to be maintained
-Take action to avoid error
Calibration of frequency
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Methods of check the accuracy of frequency
-Receive a HF standard frequency signal
-Receive a television signal as standards
-Use a GPS system
-Use a high accuracy frequency source
Calibration of frequency
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Receive a HF standard frequency signal
-Standard frequency signals at 2.5, 5, 10MHz
-Other standard frequency signals
-Accuracy of 10-9 or better
-Receiving these signal
-Comparing the frequency to these signal
Calibration of frequency
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Receive a television signal as standards
-High accuracy of television transmitters
-Accuracy of 10-11 or better sometimes
-Not all television signal are usable
-Receiving these signal
-Comparing the frequency to these signal
Calibration of frequency
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Use a GPS system
-Caesium clocks on GPS satellites
-Time accurate of better than 1s
-Frequency accurate of better than 1011
-Signal is available everywhere
-Coded signals at 1575.42 MHz and 1227.60 MHz
Calibration of frequency
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Use a high accuracy frequency source
-Calibrated frequency generator
-Caesium clock
-Rubidium clock
-Frequency accurate of better than 1011
-High cost of atomic clock
Calibration of frequency
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Calibration of measuring ormonitoring receivers
General considerations
Calibration of frequency
Calibration of measuring ormonitoring receivers
Calibration of the measuring
antennasCalibration of fixed monitoringrecording instruments
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Calibration of the measuringantennas
General considerations
Calibration of frequency
Calibration of measuring ormonitoring receivers
Calibration of the measuringantennas
Calibration of fixed monitoringrecording instruments
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Antenna factor
-A part of calibration factors that determined bythe antenna system characteristics
-Gain, cable losses, adaptor losses
-Varies with frequency
Three basic method of calibration an antenna:
-Standard field method-Standard antenna method
-Standard distance (standard site) method
Calibration of the measuringantennas
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All method deliver the antenna factors
-Valid for free space under far field conditions-Avoid influence of nearby object
Calibration of the measuringantennas
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Standard field method
-Derived from the definition of the antenna factor-Direct calibrate in an accurately known field
-Limited to loop antennas
Calibration of the measuringantennas
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Standard antenna method (substitution method)
-Measure a plane wave of unknown field-strength
-Using an antenna with known factor
-Replace it by antenna to be calibrated
-Determine antenna factor from the difference
-3 limitation
Calibration of the measuringantennas
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Standard distance (standard site) method
-Mount 2 identical antennas at different distance
-Measure the attenuation between 2 antennas-Compare with calculated value
-Normally for directive antennas
-Distance should be far enough to avoid mutualcoupling
Calibration of the measuringantennas
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Calibration of fixed monitoringrecording installations
General considerations
Calibration of frequency
Calibration of measuring ormonitoring receivers
Calibration of the measuring
antennasCalibration of fixed monitoringrecording instruments
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Initial calibration under controlled conditions
-Compare with calibrated field-strength meter and
antenna-Only valid when conditions remain unchanged
-Periodic calibration checks
-Calibration curve in the frequency range of interest
Calibration of fixed monitoringrecording instrument
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General calibration procedure
-Field-strength meter with a shielded loop antenna
below 30MHz-Field-strength meter with a dipole beyond 30MHz
-Substitute the recording antenna with the calibrateantenna
Calibration of fixed monitoringrecording instrument
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Thank you!