ETS-Lindgren 3301B Active Rod & Field Antenna (Archived) - Manual (Page 22)

22 | Principles of Operation
If both roll off switches are simultaneously set in the on position, the low
frequency 3 dB roll of point will be approximately 23 kHz.
6.3.2 Proper Selection of Internal Attenuation
When dealing with CW type signals, no attenuation is needed to measure field
strengths below 0.7 V/m. At approximately this level, the saturation indicator light
will come on. This indicates a need to switch on the 10 dB attenuator.
When the 10 dB attenuator is switched on, the Model 3301B can measure field
strengths up to 2.2 V/m without saturating. The unit retains 115 dB of dynamic
range, but the maximum reading before saturation is raised by 10 dB while the
minimum discernible signal is also raised by 10 dB. At 2.2 V/m, with the 10 dB
attenuator active, the saturation indicator light will again come on. This indicates
a need to switch the 30 dB attenuator on in place of the 10 dB attenuator.
The 30 dB internal attenuator will allow the unit to maintain calibration while
measuring field strengths up to 22 V/m. Again, the unit retains 115 dB of dynamic
range. Both the maximum reading before saturation and the minimum discernible
signal are raised 30 dB above their 0 dB attenuation values.
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 and not 30 dB.
It is unwise to use attenuation to measure very low field strengths. When the field
strength falls below the minimum discernible signal, inaccurate field strength
measurements will result.
Both of the internal attenuators have a 10% tolerance, so they should be
calibrated before being used in critical applications.
A warning about the internal 30 dB attenuator: With the 30 dB attenuator
active, the unit resonates at 30 MHz. Therefore, the unit should not be used
above 15 MHz with the 30 dB attenuator active
The usefulness of the internal attenuators for impulse response testing is
discussed in Antenna Impulse Response on page 35.
Archived 3/18/10