Manual FCKL 1528 Page 5
4 FCKL 1528 Displays and controls, description
4.1 Reading of the interference voltage in dB
µµ
V
Analogue reading of the inference voltage according to the detectors in dB over 1
µ
V.
If the attenuator (2.2) and (2.3) is set to 0 dB, the meter reading is directly in dB
µ
V in a
50-ohm-system, assumed that the input switch (8.2) is in the direct input position and
switch (4) is in one of the centre Low distortion positions.
The upper meter reaches from -25 dB to +25 dB with good linear dB-scaling. This
means a logarithmic voltage reading which is related to 0 dB in the centre of the scale.
This logarithmic overview range is active, if switch (4) is in one of its right hand
positions. This overview range permits quasi peak measurements, but there are
limitations when very slow pulses occur and the reading is more than +10 dB on the
meter.
Because of the fact that the logarithmic scale goes down to -25 dB, there is a basic
reading caused by noise for Low distortion (4).
As this noise floor is very low, this is no restriction for practical measurement.
The lower meter gives a linear voltage reading. Because of the logarithmic law
between the dB level and the voltage the density becomes higher and higher on the left
side.
The definition is very high in the range between -5 dB to + 6dB.
This linear voltage range is best choice for high precision measurements based on the
comparison between the signal to measure and the calibration signal.
The input signal is attenuated down to the level (2.2) and (2.3) of the internal calibration
signal.
4.2.1 Attenuator display (attenuation in dB
µµ
V)
This 4 digit display (3 digits plus sign) is the result of the attenuation of the step
attenuator (2.3), the high power 10 dB attenuator at the input (8.2) and the 20-dB i. f.-
attenuator, which is active in the extreme left and right positions of the switch (4).
This dB-number plus meter reading is the interference voltage in dB over 1
µ
V
according to the detector standards.
If the magnetic antenna FMZB 1516 is used and the input switch (8.2) is in the right
position, the reading is dB over 1
µ
A/m or in the equivalent electric field-strength in dB
over 1
µ
V/m. In the case of the magnetic field negative dB
µ
A/m-numbers can occur.
4.2.2 10 dB-steps of the input attenuator
With the 10 dB-step attenuator the desired level range of the receiver is controlled. The
dB number visible in (2.1) corresponds to the 0 dB-marker in the centre of the meter
scale and to the 0 dB horizontal centre line of the xy recorder diagram.
The left end of this line touches a small rectangular area, in which this dB number has
to be written.
At the right end of the line the relative level has to be introduced.