On 7/25/2012 8:47 AM, John S wrote:
On 7/23/2012 11:21 AM, Jeff Liebermann wrote:

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. From the manufacturers web pile at:
http://www.hoperf.com/rf_fsk/
they offer +10, +13, and +20dBm outputs and claim they all meet ETSI
and FCC regs. I dunno about that.


I looked at one of the Hoperf parts and found this:

"The RFM69H is intended for applications over a wide frequency range,
including the 433 MHz and 868 MHz European
and the 902-928 MHz North American ISM bands."

That's the catch. Although it is capable of operating at 10dBm on 433,
you are responsible for only doing that in Europe where it is legal.
Otherwise, you may operate it at its maximum power capability here in
the US on 915MHz. Under those conditions, it complies with FCC regs.


Continuing the investigation, I find that the US has no ISM band
anywhere near 433MHz. The closest is 915MHz.

Interestingly, on that band, the FCC says:

"§ 18.305 Field strength limits.
(a) ISM equipment operating on a fre-
quency specified in § 18.301 is permitted
unlimited radiated energy in the band
specified for that frequency."

Wow! Unlimited!

The catch is that you may have no emissions outside the ISM bands
exceeding 25uV/m at 300m. That would be equivalent of less than 2
microwatts of 2nd, 3rd,.... etc, harmonics and other stuff being
radiated by the antenna. That, I think, would be about -37dBc when
running 10mW. The more power you run, the harder it gets to filter.

In addition, I still have some questions in my mind about certification.
Just because a manufacturer says it will meet the requirements, doesn't
necessarily mean it is certificated. Part 15 (not ISM) allows us to
build our own transmitters which are not for sale. But, I can find no
mention of that in part 18 (ISM).

Still lots of questions out there.