"Jeff Liebermann" wrote in message
...
On Sat, 18 Jul 2009 19:20:04 -0700 (PDT), ve2pid
wrote:

Hope that my question has some sense...: If we double the power
radiated by an antenna (+3 dB), how does it translate on the S-meter
at a receiver 'far' away.. i.e. is the difference in dB on that meter
has some mathematical relation to the 3 dB change at the transmitter?

One S unit is allegedly 6dB. Doubling the power would therefore be
about 1/2 an S unit.
http://en.wikipedia.org/wiki/S_meter


I've heard the same thing, but the reality is that the S-meter usually
follows the AGC and the signal for S9 could be different for every design.
But Flex radio and others define S9 as 50 uV.

Long time past, I heard that S9 was a noise free signal. But "noise free"
is undefined. 30 dB SNR? 40 dB SNR?

Imagine that your S-meter is perfectly logarithmic and your SNR is 54 dB at
S9. That's one way to get 6 dB per S-unit.