Manual FCKL 1528 page - 22
12.2.2.1. Linear scale
Obviously the linear scale has no linear scaling (equal distances for dBs), which is
somewhat of a contradiction.
The explanation for this strange behaviour is that the scale behaves linearly concerning
voltages in V or
µ
V, not dB
µ
V.
The receiver converts the voltage on is input connector into proportional readings on the
meter.
If we would make a scale in V or
µ
V, this scale would be a linear scale.
However the scale used is a dB
µ
V-scale, according to a logarithmic law.
Because of this logarithmic law the distances increase from left to right.
The table below shows this for some characteristic values.
Input voltage is in
µ
V and the attenuator setting is 0 dB.
Input voltage in
µ
V
Meter reading on the linear scale
0,316
µ
V
-10
0,354
µ
V
-9
0,398
µ
V
-8
0,446
µ
V
-7
0,501
µ
V
-6
0,501
µ
V
-5
0,630
µ
V
-4
0,707
µ
V
-3
0,794
µ
V
-2
0,891
µ
V
-1
1,000
µ
V
0 dB Centre of Meter
1,122
µ
V
+1
1,259
µ
V
+2
1,413
µ
V
+3
1,584
µ
V
+4
1,778
µ
V
+5
2,000
µ
V
+6
For the difference of 1 dB from -10 dB to -9 dB only an input voltage difference of
0,122
µ
V is needed.
For the difference b5 dB and +6 dB we need 0,686
µ
V, nearly 6 times more.
This corresponds to the distances in the dB-scaling.
