[Elecraft] S-Meter Sensitivity

[Vic Rosenthal]

Lyle Johnson wrote:

> Not that it *really* matters, since the "S meter" is just an aid,
> not an absolute measuring device :-)

Indeed.  I might point out to all of those guys who feel a need to trace their
S-meter calibration back to the platinum-iridium standard 'S' which is kept in a
vault underneath the former site of W6AM in Palos Verdes Estates, that the
reading of the s-meter depends upon (among other things):

1) The absolute gain of the antenna in the particular direction of the signal.  
This varies with the type and size of the antenna, height above ground,
directivity, etc.

2) The impedance seen by the receiver at the frequency in question.

So the absolute number of microvolts that cause the meteer to read S9 is
unimportant.  it's almost impossible to make comparisons between signal reports
at different locations.  What an S-meter IS useful for is to compare two signals
received at the same location.  You are interested, therefore, in the number of
DB per S-unit on your meter.  If you have a calibrated attenuator and a
variable-output signal generator, you can find out how much each bar is worth
(and whether they are all the same or what).  Then when a guy asks you "which
antenna is better?", you can tell him in DB.

73,
Vic, K2VCO
Fresno CA