On Tue, 24 Jul 2012 09:10:20 -0500, John S
wrote:

On 7/23/2012 4:03 PM, Jeff Liebermann wrote:
(...)
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.

Oops and thanks (again). I keep fudging the numbers (unintentionally)
to what I think they should be, instead of what they are. Very
embarrassing.

Microwatts doesn't seem to make sense as there are products being sold
that advertise 10mw and 100mw output power levels. Obviously they are
not being certified under Part 15. However, I can't find another US
service on 433MHz that qualifies (except ham radio). FCC frequency
allocations table is of no use:
http://ecfr.gpoaccess.gov/graphics/pdfs/er27ja12.018.pdf
433MHz is an ISM band, but only in region 1 (Europe) and not in region
2 (US).
http://en.wikipedia.org/wiki/ISM_band
My guess(tm) is that the higher power 433MHz devices can only be sold
in Europe. Yet, that's not apparent on any of the sites selling
433MHz data radios.

"FCC Compliance testing Using the MICRF112"
http://www.micrel.com/_PDF/App-Notes/an-55.pdf
Page 9 has the calcs for a typical key fob transmitter.
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.

I'll do some more reading and checking, hopefully tonite. Paying work
comes first. My appologies (again) for my multiple screwups.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558