ETS-Lindgren 3301B Active Rod & Field Antenna (Archived) - Manual (Page 28)

28 | Setup and Use
8.2 High Sensitivity Readings
The Model 3301B is optimized to facilitate extremely sensitive readings. For best
performance, all internal attenuation should be off. The gain switch should be
placed in the low gain setting. The noise limiting factor on the Model 3301B is the
high front end impedance presented to the FET. So when the gain stage output
is increased with the gain switch, the noise is also amplified and actually
increased slightly due to additional noise added in the gain state. The high gain
setting is primarily intended to provide additional signal strength for receivers that
require it
A set of minimum discernible signal graphs is included in this manual. These
graphs represent the smallest signal which can be detected with the
Model 3301B. 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.
Several typical bandwidths are presented. To calculate the expected sensitivity at
some other bandwidth, a 10*log relation should be used.
E XAMPLE
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 –2 dBuV/m. The ratio of the bandwidth is 3/1=3. Taking 10*log(3), we get
4.77 dB. Therefore, the expected sensitivity would be –
2dBuV/m+4.77dB=2.77dBuV/m.
Archived 3/18/10