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Minimum
recommended specifications for analogue and digital radio
monitoring receivers are described in the
Spectrum
Monitoring Handbook (Edition of 2002).
One
of these specifications is for example the 3rd order intercept
point level (IP3), a measure of the receiver’s linearity. The
higher the IP3 level (usually expressed in dBm), the better the
linearity of the receiver is. The full importance of this
specification comes out when the receiver operates in an
environment of many high level emissions in the spectra vicinity
to the tuned frequency – that is a frequent scenario in a
monitoring station.
Limited
linearity of a receiver is one of the reasons for the monitoring
operator to get signals that do not really exist in the RF
spectrum. These spurious signals are generated in the equipment
itself. They make the radio monitoring task difficult and
tedious and may conduct to wrong results and false reports.
When
comparing the data sheets of similar receivers from different
manufacturers, the IP3 levels indicated are considered by the
users, among other parameters, for the purpose of receiver
quality comparison.
To
be able to get a fair comparison between the receivers, however,
they all should have been tested under the same conditions.
Otherwise, Receivers from different makers showing nearly the
same IP3 levels in their respective data sheets, might |
