revisiting the 434 MHz band

Werner Almesberger werner at openmoko.org
Wed Jul 21 20:55:52 EDT 2010


More on regulations and transmit power:
http://www.silabs.com/Support%20Documents/TechnicalDocs/AN421.pdf

Note that they don't say anything about the type of application,
duty cycle, etc. E.g., the 434 MHz band figures, low as they are,
assume the 11 mV/m limit from FCC 47.15.231(a), which comes with
a lot of use restrictions. FCC 47.15.231(e), which only restricts
the duty cycle to 1/30 would reduce the limit to 4.4 mV/m.

To be rid of all use restrictions FCC imposes on the 434 MHz band,
transmit power could only reach 200 uV/m, which - using the data
from table 1.2, which assumes ideal propagation but the presence
of real-life interferences - should allow data transmission at
9600 bps over a distance of 6 m, or 3 m at 57 kbps.

- Werner




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