> How many db increase for every one S-unit, using as factory
> standard ??.
> de YD1BIH
it depends by each factory....
Following conventions (traditions) it should be 6 db per S unit and 50
uV for S-9 in HF. Someone had 5 db per division (Drake, for example, if
I remember correctly) likewise most Japanese RX float and read S9
already with less than 10 uV.
Actually, the majority of S meters do not work well, in the range
between S1 and S-5 they are mostly linear (i.e. 1 dB per division),
between S5 and S9 they start to indicate something that's anyway not
constant and vary between 3 and 6 dBs per division, over S9 they *show*
their best that's often a *poor best*.
Knowing that's not easy to deal with an AGC voltage in the way to
produce a constant S-meter movement, in the digital era it's easy to
correct the readings associating the correct offset to different AGC
voltages and also taking in account for attenuators or preamplifiers.
It seems design engineers still do not consider this opportunity that's
instead widely used in other equipments.
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