On 7/23/2012 12:30 PM, Jeff Liebermann wrote:
On Mon, 23 Jul 2012 11:54:01 -0500, John S
wrote:

On 7/23/2012 11:21 AM, Jeff Liebermann wrote:
On Mon, 23 Jul 2012 08:56:41 -0500, John S
wrote:

On 7/23/2012 1:28 AM, Jeff Liebermann wrote:
On Sun, 22 Jul 2012 23:21:12 -0700, Jeff Liebermann
wrote:

FCC 15.209
http://louise.hallikainen.org/FCC/FccRules/2012/15/209/
200 uv/meter maximum, measured at 3 meters. That works out to about
-46dBm ERP or about 12 milliwatts into a unity gain antenna.

Sorry, brain damage.
The -46dBm should be 10.8dBm ERP

Hmmm... my calculator says P = 12 nanowatts.

Your calculator is correct. My -46dBm is wrong. It was late, I was
multitasking, the phone range, I was tired, etc. Sorry for the
muddle.
+10.8dBm converts to 12 mw.

12 nw is -49 dBm. Why are you still using 12 mw?

The 12mw is correct. The -46dBm was my mistake. It should
have been about +10.8dBm.

http://www.rapidtables.com/convert/power/dBm_to_mW.htm

Then... I find a 433MHz radio that delivers +20dBm (100mw).
http://www.sparkfun.com/products/10153
By my reading of 15.209, that's overpowered unless operating with a
miserable -9dB gain antenna.

The antenna would have to have -69 dB gain for 100 mw to radiate 12
NANOwatts.

Nope. Use 12 milliwatts or 10.8dBm please. Loose the -46/49dBm.


Oh, I see.

You used 100 MILLIvolts (not MICROvolts) in your calculation! That's how
you wound up with MILLIwatts rather than (NANOwatts).