Zhao,
My first thought, from running my own experiments is that it has
something to do with the transmission power. 9 m is about what I would
see with the mica2 in 900 MHz(it uses the same hardware as 433 MHz, but
a couple capacitor values are different) when i set the transmission
power to 0x02 (which by the data sheet should be -20 dBm).
However, there can be many reasons why the transmission range is short.
Are there any obstructions between the two motes? Are you using the 433
MHz antennas (they should be somewhere around 17 cm long, I don't
remember off-hand, but the 900 MHz whip antennas are approximately 8 cm
long)? Are the antennas oriented vertically on both motes? Are you
aware of any other devices operating in the 433 MHz frequency range? If
the the motes are battery powered, are they running low? How are you
setting the frequency, are you manually tuning or using a preset? (If
you are manually tuning, i recommend using one of the 433 presets for
control purposes)
A couple of things I would recommend you try:
1) Try using the default power level (0x80) <- hex, not decimal and
see what range you achieve. When chaning the power level, make sure you
only use values listed on the CC1000 data sheet, otherwise you might get
unexpected results. i.e. Going from 0x0F to 0x10, you will actually see
a decrease in transmission power.
2) Try a different pair of motes, it is possible that one or both
of the motes you used have hardware problems. The antenna connector
might not be fully soldered on, etc.
3) Try the experiment in another location
Hope this helps,
-Paul
On 12/10/2009 6:08 AM, Zhao Stephen wrote:
Dear all
I just test the rf coverage of mica2 in outdoor. two mica2 nodes are
used, one is transmitter and the other is receiver. But the maximum
range is around 9 meters, beyond that the receiver has no response. It
is normal? In my setting, mica2 use 434Mhz and
CC1000ControlM.SetRFPower(255).
Why?
Thanks
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