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INSTRUCTION MANUAL
AM-741R
ACTIVE MONOPOLE ANTENNA
1912 1 E l T o ro R d
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Si l vera do, Ca lifo rni a 9 26 76
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(9 49) 459 -96 00
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co m-p o wer. com
REV112216
4.0 Measurement Correction Factors
Anyone familiar with EMI radiated emissions measurements understands that
‘uncorrected’ values measured on your spectrum analyzer or EMI receiver are essentially
meaningless without the appropriate ‘correction’ factors for the individual components
of your measurement system.
A typical radiated emissions measurement system can include any combination of the
following components, all of which have a quantifiable effect on the measured voltage;
and therefore must be accounted for to accurately ‘correct’ your reading:
•
Receiving antenna(s)
•
Preamplifier(s)
•
Coaxial measurement cable(s)
•
Attenuation Pad(s)
•
Connecting Adapter(s)
•
Low-Pass, High-Pass or Notch Filter(s)
•
DC Block(s)
•
Other similar measurement components
We can separate the factors associated with the above components into three basic
categories:
1)
Antenna (or transducer) Factors,
2)
Gain Factors (for preamplifiers); and,
the cables, attenuators, adapters, filters, etc., can all be lumped into one general
category…
3)
Insertion Loss Factors
These three categories of correction factors are discussed in the following sections.
Most of today’s spectrum analyzers and EMI receivers allow entry of these factors directly
into the instrument. You can then group the factors into factor sets. This makes things
very convenient, and allows the instrument to display/output test results as the corrected
values, with no further correction necessary. These newer instruments will also allow you
to enter the specification limits, so that PASS/FAIL can be determined instantaneously.
Older instruments, however, do not have this capability, so manual correction, or
correction through data acquisition PC software (or other means) is needed.
Whatever the case may be, applying the
CORRECT
correction factors is obviously key to
achieving accurate results. A simple typo when entering factors into your instrument or
PC software will give you incorrect data
every time a test is performed
until such time
that you notice the mistake, or until you recalibrate and enter the new factors. It is a
good idea to double-check your entries.
