On Jun 2, 2008, at 7:43 AM, Al Williams wrote:
> Is the gain reported in antenna models a gain of: E (electric
> field), I (magnetic field), or W(watts-W=EI)?
>
> Also, Is the S meter in receivers in E (S9=50 microvolts) still in
> E when the scale switches to x DB over S9?
>
All of the above.
Gain is a ratio. It is normally expressed in decibels (dB), which is
10 log (P/P0) or 20 log (E/E0). Since P = I^2R = E^2/R, gain in
decibels is independent of whether you are measuring voltage, current
or power.
Likewise, an S meter nominally has a logarithmic scale, which can
refer to power, voltage or current. The S units (below S9) are
usually stated as 5 or 6 dB, but unfortunately S meters notoriously
vary greatly between receiver manufacturers and models, so are not a
very accurate measure of even relative signal levels.
73,
Bob, N7XY
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