Hi Marcus, > On 11/10/2020 07:06 PM, Lukas Haase via USRP-users wrote: >> >> The reason why I am asking about this is because I would like to cross-check >> my measurements. >> >> My original question was about RX gain but it actually also relates to TX >> gain. >> >> With an X310 and UBX-160, TX Gain=0 and sending out a full-scale sinusoid at >> 915MHz, I measure approx. -2.5dBm. >> >> This is not consistent at all with the file above (assuming I interpret how >> "gain" is defined correctly, hence my original question). >> >> Would anyone with an UBX-160 be so kind to confirm/disconfirm which power >> level I would expect to see? >> >> (Preferably at 915MHz with TXgain=0 and full-scale sinusoid but I'm happy >> with any other configuration that I can x-check).
> So, according to the charts, at 900Mhz, you'd expect about -9dBm with a > 0dB gain setting, with a full-scale baseband signal. > > So, there's a discrepancy of about 6.5dB. Exactly. That's a bit too much for my taste and hence maybe my measurement is wrong. > How did you measure the power > level? I could easily expect a couple of > dB discrepancy just due to component batch-to-batch variability. > So, how was the power measured? I know, ideally you'd use a powermeter for that. But I don't have one. Instead I have a VNA (Agilent E5080A) which is freshly calibrated and hence the power measurement is very accurate (<<0.5dB). I set the measurement as "B Source Port 1" which gives directly the received signal in dBm. I pick a "reasonable" IF bandwidth (50kHz), 100x averaging, save the dBm/f trace to a CSV file and import into MATLAB. Then I integrate over the frequency: deltaF = frequencies(2)-frequencies(1); Ptot = 10*log10(trapz(10.^(PSD/10)/RBW)*deltaF); I can verify that the integrated power is roughly the same as the marker on the frequency. Having said that, I just realized something very, very weird: With the UBX-160 I set: fcenter=915MHz, samp_rate=5e6, TXgain=0 and send a full scale, complex sinusoid with 1MHz. Hence I would expect to see one tone at 916MHz and a small one (due to I/Q mismatch) at 914MHz. However, instead I get the spectrum attached. There is another tone at 910 MHz and the spectrum is centered at 913 MHz (should be 915). That makes no sense! What could be going on here? Thanks, Lukas _______________________________________________ USRP-users mailing list [email protected] http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
