[TowerTalk] ant model gain

[Bob Nielsen]

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