On 7/23/2012 4:03 PM, Jeff Liebermann wrote:
On Mon, 23 Jul 2012 12:41:32 -0500, John S
wrote:

From the document you posted, P*G/(4*Pi*D^2) = E^2/(120*Pi)
Let G = 1, D = 3, E = 200uV then
P*1/(4*3.14*3*3) = (200e-6)^2/377 and
P/113 = 40e-9/377 so that
P = 113 * 106e-12 giving
P = 12e-9
This looks like NANOwatts to me.

Well, that looks right. I'll do the short version:

From Pg 29.
http://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet63/oet63rev.pdf

Assuming a 0dBi gain antenna:
Power = 0.3 FS^2
where
FS = field strength in Volts/meter
P = Watts
Plugging in:
Power = 0.3 * (200 uV/m)^2 = 0.3 * (200*10^-6 V/m)^2
Power = 0.3 * 4*10^-8 = 12*10-9 = 12 nano watts.
Argh... You're right.

However, that can't be the correct maximum power. It's much too low
to be useful.

Digging out a cheat sheet from:
http://www.ti.com/lit/an/swra090/swra090.pdf
CEPT (European) 1e and 1e1 are 10mw and 1mw respectively.
However, digging down to the FCC stuff on Pg 11, I find that the specs
are really in FCC 15.231(b).
http://louise.hallikainen.org/FCC/FccRules/2012/15/231/
and are approx 11,000 uV/meter. Grinding the numbers again...

Assuming a 0dBi gain antenna:
Power = 0.3 FS^2
where
FS = field strength in Volts/meter
P = Watts
Plugging in:
Power = 0.3 * (11000 uV/m)^2 = 0.3 * (11000*10^-6 V/m)^2
Power = 0.3 * 0.000121 = 36 milliwatts.


..3 * .000121 = .000036 or 36 MICROwatts.

Thanks for catching my mistake and I'll double check the numbers
(again) when I get home from some service calls.


You're welcome again.