ETS-Lindgren 3301C, User Manual

Page: 39 / 62

Operation
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When using either of the attenuators, make sure to add the attenuation to the
antenna factor for accurate readings. Also, note that if both attenuator switches
are used, the resulting attenuation is approximately 31 dB.
Both of the internal attenuators have a 10% tolerance, so they should be
calibrated before being used in critical applications.
For High Sensitivity Readings
The Model 3301C is optimized to facilitate extremely sensitive readings. For the
most sensitive applications, all internal attenuation should be off. The noise
limiting factor on the Model 3301C is the high front end impedance presented to
the front end of the wideband amplifier.
The signal graphs provided in
Data and Illustrations
on page 49 represent the
smallest signal which can be detected with the Model 3301C.
The data plotted are the noise output of the unit. As a
result, this forms the noise measurement for a signal plus
noise to noise ratio of 3 dB.
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Several typical bandwidths are presented. To calculate the expected sensitivity
at another bandwidth, a
10log relation should be used.
Example
Determine the sensitivity with a 3 kHz bandwidth at 1 MHz:

The minimum discernible signal (MDS) at 1 MHz with a 1 kHz
bandwidth is read from the graph at
7 dBuV/m

The ratio of the bandwidth is 3/1=3

Taking 10log(3) results in 4.77 dB

Therefore, the expected sensitivity would be
7 dBuV/m+4.77dB=11.77dBuV/m