Thank you for answering but I cannot understand what you mean with "The USRP is not a measurement receiver". If USRP was not a measurement receiver, which is its utility? Moreover, if it is not a measurement receiver what is the result memorized in m.data that is the output of usrp_spectrum_sense.py? When I use a WiFi antenna I can receive (and measure) the energy of WiFi channels. The problem arises without antenna becasue USRP measures a signal that cannot exist! Furthermore, such a signal is always at the beginning of the sensed bandwidth, so this has not any sense!
Any idea about that? Thank you! Nick Foster-4 wrote: > > On Wed, 2011-05-25 at 08:51 -0700, Lebowski80 wrote: >> Hello everyone >> >> I’m using an USRP with a XCVR2450 daughter board working at 2.4 - 2.5 >> GHz. I >> want to find a threshold between thermal noise and signals energy using >> the >> script usrp_spectrum_sense.py and sensing from 2.400 GHz to 2.500 GHz. To >> do >> that, I replaced the WiFi antenna with a resistor of 50 Ω to measure the >> noise. I obtained a very strange peak at the beginning of the bandwidth >> (around 2.405 GHz) and this result was totally unexpected because I >> supposed >> to sense only thermal noise without any particular peak. So, I repeated >> the >> experiment from 2.420 GHz to 2.500 GHz and I achieved the same peak >> always >> at the beginning of the bandwidth (in this case around 2.425 GHz). >> Therefore, I'm quite sure this is a problem linked to USRP or to the >> script >> usrp_spectrum_sense.py, isn’t it? Can someone give me a hint about that >> please? > > The USRP is not a measurement receiver, and some small spurs are to be > expected. You can plan for this, or work around it by changing the LO > offset at a given center frequency using the advanced tuning parameters: > http://www.ettus.com/uhd_docs/doxygen/html/structuhd_1_1tune__request__t.html > > --n > >> >> Regards >> > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://old.nabble.com/Unexpected-energy-peak-sensing-thermal-noise-and-using-usrp_spectrum_sense.py-tp31700266p31705762.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio