Electro-Metrics EM-2115, Instruction Manual

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ELECTRO-METRICS EM-2115 2.0 OPERATING INSTRUCTIONS
(EM2115S2-9)
(LED) will flash rapidly unless the correct quasi-peak IF bandwidth is selected for the Frequency
Range being used. While measurements can be made in the Quasi-Peak position with an invalid
Q.P. IF bandwidth selected, the measurements will not conform to CISPR and related specifica-
tions/requirements.
The IF bandwidths marked in black plus the 200 Hz IF bandwidth are normally used
when measurements to MIL-STD plus other applicable military, government, and commerical
standards are required.
2.4.4.1 Bandwidth Selection Criteria
To obtain the best sensitivity and selectivity from a narrowband signal, select the narrow-
est IF bandwidth. A problem with this approach is that all the sidebands of a modulated CW sig-
nal may not be included in the measurement, plus a CW signal is more difficult to tune with the
receiver set to the narrowest IF bandwidth. In addition, this setting will be the least sensitive to
broadband signals.
NOTE: Refer to 2.4.7 for broadband--narrowband determination.
For most measurements, select a medium IF bandwidth setting unless maximum selectivi-
ty or maximum narrowband--broadband sensitivity is required.
Use a combination of medium and narrowest bandwidths when measuring a signal to de-
termine the following:
a. If both measurements are within 1 dB of each other, any modulation on the signal
is contained within the narrower bandwidth.
b. If the medium IF bandwidth measurement is 2 dB to 6 dB higher than the narrow-
est IF bandwidth measurement, it is likely that some or all of the signal sidebands
fall outside the passband of the narrowest IF bandwidth. In this case the wider IF
bandwidth measurement should be used. However, in the wider IF bandwidth, it is
also possible that nearby signals or receiver noise is influencing the measurement.
c. If the difference between the two IF bandwidth measurements is greater than 7
dB, the signal should be classified as broadband for both bandwidth measure-
ments. However, as in b, receiver noise and/or nearby signals may be influencing
the wider bandwidth measurement.
The widest available IF bandwidth will have the poorest narrowband sensitivity and se-
lectivity but broadband sensitivity will be greatest along with easiest signal tuning. The widest IF
bandwidth should be used for peak broadband signal measurements plus quickly acquiring and