RECEIVER SETUP
Section 6, Page 11 May 2002
QUALITIES OF A GOOD CALIBRATION
Since all data will be normalized by the system calibration, it is important to ensure that the
calibration is reasonable immediately after it is acquired. (All calibrations are written to
memory. If the operator does not verify the calibrations, a bad calibration can be replaced later
during data processing; but it's always better to catch the problem in the field.)
Table 6.1 (below) lists values from a typical RPIP calibration. Remember calibrations
incorporate the electronic characteristics of each individual receiver, so the numbers may vary
depending upon the filters and other components in a particular receiver.
The magnitudes in the Calibration Cache will differ from the magnitudes shown on the display
while the calibration is in progress. This is because the initial magnitudes are raw values, while
the values stored in the caches have been normalized to the calibration voltage and have been
corrected for any gain differences in the individual channels.
QUESTIONABLE CALIBRATIONS
If a calibration differs significantly from a known, correct value for a particular instrument, and
that difference cannot be due to recent hardware modifications, there may be a system problem.
Consult Section 15 - Maintenance for trouble-shooting. Otherwise, an error may have been
made in the calibration set-up. Re-check the set-up procedure. Common errors include:
Incorrect wiring to the input channels for an external calibration.
Checking the calibrations using a notch filter setting different from the calibration setting.
If a bad calibration is discovered before any data is taken, simply re-run the calibration. This
replaces the old values with the new ones. Either erase (initialize) the old calibration first or run
the new calibration at the same frequencies. This avoids the problem of combining old
calibration data with new.
If an invalid calibration is discovered after taking data, the data can be saved.
1. Dump the bad calibration file into a file on a personal computer (See Section 7.6).
2. Recalibrate the receiver, and dump this file to the personal computer (See Sections 6.1,
7.6).
3. Process the data through the Zonge SHRED program, and provide both the good and bad
calibration files. SHRED will remove the bad calibration and renormalize the data with
the good calibration.
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