revisiting the 434 MHz band

Wolfgang Spraul wolfgang at sharism.cc
Thu Jul 22 02:30:50 EDT 2010


Werner,
did you mention recently that you found SPI test points on the PCB behind
the LCM? If so we should definitely document that. Do you think we can
hookup HopeRF modules to those test points?
I plan to send you a few HopeRF modules soon, and also some more plastic
parts and stuff to play with.
Thanks a lot for all your feedback, very appreciated!
Wolfgang

On Wed, Jul 21, 2010 at 09:55:52PM -0300, Werner Almesberger wrote:
> 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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