Yep, Brian's right. Doing what you propose would be equivalent to reducing the DAC to ~7bit and thus reducing signal-to-quantisation-noise-ratio by 54dB (!). You don't want that.
Try subdev.set_gain(). You can see the available gain range with subdev.gain_range() (subdev is the object to access the subdevice, try usrp.selected_subdev() ). Perhaps that will help. MB On Wed, Jan 21, 2009 at 01:05:50AM -0500, Brian Dunn wrote: > Hi Yong, > > I think with maximum signal levels of +/- 45 on the digital side your > signal would be severely distorted due to quantization noise. Perhaps the > easiest thing to do would be to put a mini-circuits attenuator inline with > the SMA output of the RFX2400 board? Not sure if this will work for your > application though. > > -Brian > > > On Jan 20, 2009, at 8:37 PM, Yong J. Chang wrote: > >> >> Hi, all! >> >> Now I'm using USRP1 and RFX2400 d'board. In our project, we have to be >> able >> to reduce transmit power down to -40dBm. Please correct me if my approach >> is >> wrong. >> >> If we set tx_pga=0dB, the transmit power only depends on the level of >> signal. So, +/-32767 can give us maximum transmit power 17dBm because the >> maximum transmit power of RFX2400 is 17dBm. >> >> Since the power is a square of signal level, we can get -40dBm if we >> choose >> signal level +/-45 roughly. >> >> Am I right? >> >> -- >> View this message in context: >> http://www.nabble.com/RFX2400-Transmit-power-tp21575529p21575529.html >> Sent from the GnuRadio mailing list archive at Nabble.com. >> >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> [email protected] >> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio -- Dipl.-Ing. Martin Braun Phone: +49-(0)721-608 3790 Institut fuer Nachrichtentechnik Fax: +49-(0)721-608 6071 Universitaet Karlsruhe (TH) http://www.int.uni-karlsruhe.de/
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