NARDA ELT-400, Руководство по эксплуатации

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Annex B: Exposure STD mode ELT-400
B-4
Please note
When you compare the results from the ELT-400 in “Exposure STD” mode
with those from other field measuring instruments, some possible factors
that need to be taken into account are:
•
The comparison system must also measure isotropically and combine
the results from the thee channels correctly.
•
The different bandwidths and the lower frequency limits of comparison
instruments can affect the results considerably.
•
The broadband measurement most often used can only be used for
single-frequency fields. This method does not give a reliable result if the
signal shape is unknown. Any frequency measurement that may be
performed can be subject to extreme errors, so it is impossible to
stipulate the correct reference values.
•
The effective cross sectional area and the positioning of the
measurement sensors (i.e. distance from the field source) significantly
affect the results, particularly in the near field.
•
FFT analyzers usually show the results as peak values. The
corresponding reference values from the standard should be applied.
Spectral components must not be ignored. The recording period of
1 second should also be taken into account.
If the results of isotropic (three channel) FFT analysis are combined, the
phase information is lost. Linear summation of the individual results for
each spectral line leads to a high measurement result that is usually
much higher than the real value.