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Old July 25th 12, 02:47 PM posted to rec.radio.amateur.antenna
John S John S is offline
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Posts: 550
Default 315mhz/433mhz transmitter

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.
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. 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.