1) What you are doing is correct. What's the power of your signal generator? I was using -40 dBm, and as Marcus says, that is strong, but you'll need to have a good SNR since the noise bandwidth is ~250 kHz. Several posts ago you stated running -8 dBm into the WBX. You may have damaged the WBX, since that 30 dB difference is about the isolation you may get with a damaged amp. I suggest sniffing down the chain of the WBX with a spectrum analyzer, make sure the two amps are working. Also as Marcus said, you need to be using the same bandwidth and decimation, or that will change the calibration factor.
I choose 250 kHz wince I was working with WBFM channels. 2) If the RX gain is changed, then the k must change to compensate. See my *.grc I linked in the last post. I assigned RX gain to a QT slider then added it to K. The RX gain can be changed and the RX power stays about the same. 3) I'm on travel now so I don't have access to my computer. You ought to update to GR 3.7; lot's of nice features, and it also preserves the flow diagram even if the blocks of changed. Thanks, Lou KD4HSO Gayathri Ramasubramanian wrote > Hi > Thank you for your note. > My questions here are just based on my previous measurements and your last > mail. kindly clarify the same. > > 1) Is it possible that different USRPN210 devices with WBX boards have the > different calibration factors. I set the channel gain to 0 and still get : > @ 400 MHz : k = -62.8 > @ 900 MHz : k = -58.5 > @ 1800 MHZ: k = -52.5 > > I checked the above with 3 USRPN210 +WBX devices and found the K value to > be very close to the stated values. Your values seem to be different , > Hence the question. > > My method was that I first ran the flow graph with channel gain as 0 and k > as 0. Then found the power value displayed for the 'channel_power_dBm'. > I subtracted this value from my input signal value (from signal generator) > and found out the difference. This is what I am taking to be the 'k' > value. > If I use k values (62.5 for 400 MHz) it in the block too, it give the > 'channel_power_dBm' value to be very close to the input signal generator > value. > I repeated this for 3 devices at the 3 frequencies. > > Is this correct or am I doing something wrong. As my values seem to be > almost 30 ~ 33 higher than ones you are getting from your tests. what > could > be causing this error/ discrepancy. > > 2) In you mails you say that we have to subtract RX gain from Calibration > factor to baseline it for RX gain = 0 dB . Also in one of your previous > mails you had sated that you get k = -34.5 wih RX gain of 15. So in view > of > these two stmts, was your 'k' value of -34.5 for 1800 MHz. > > This 1800 MHz is the only one satisfying this rule with previous data set: > i.e *-34.5 - 15 = 19.5 *( this is close to the 1800 MHz results you have > written about in your last email). I just want to check if my > understanding > is correct and Im doing the math right. > > 3) Could you kindly paste a picture of your flow graph for spectrum > calibration along with the xml file like last time. Using the xml to know > which bock is specified is a little tough. Having a visual flow graph > along > with the xml would be more effective to understand and relate between > them. > > > Please clarify above. Look forward to your response. > > > Thanks > Gayathri -- View this message in context: http://gnuradio.4.n7.nabble.com/GR-USRP-and-GPIB-measurements-tp49727p50090.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
