Marcus, Speaking on the topic of calibration. Has anyone characterized the performance of the Ettus daughter cards, i.e. noise floor and freq/volt measurements to card output?
--Colby On Thu, Apr 28, 2011 at 6:41 AM, Marcus D. Leech <[email protected]> wrote: > On 28/04/2011 7:38 AM, Patrik Tast wrote: > > Hi All, > > How do I convert the value from a number sink to dBm? > GRC attempt > http://www.poes-weather.com/~patrik/1.7GHz/HRPT/April-27th-2011/Screenshot-GRC.png > Output > http://www.poes-weather.com/~patrik/1.7GHz/HRPT/April-27th-2011/Screenshot-7.png > > > Regards, > Patrik > > First, received signal *power* is proportional to the square of the received > *voltage*, and the received *voltage* (instantaneous) is > what comes out of a USRP source block. > > I usually feed into a complex-to-mag-squared block, followed by a > single-pole IIR filter, then I decimate it with a keep-one-in-N block to > reduce > the data rate. Now, after this, you have an unscaled estimate of the > signal strength across whatever bandwidth is "seen" by the > complex-to-mag-squared block. If you want to scale it into dBm, then run > it into a log10 block, and set 'n' to 10, and 'k' to whatever > calibration constant you have determined experimentally will map your > power estimates into actual received dBm. > > Here's the thing. None of the hardware involved here is intended/designed > to be a precision measuring instrument. So you have to calibrate > according to your own local setup so that you get dBm numbers that make > sense. Those calibration constants can, and usually will, change > with frequency, since most garden-variety amplifiers, mixers, etc, aren't > perfectly flat across their operating frequency. > > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
