# Upconvert Signal with USRP N210 in GNU Radio Companion

I'm using a USRP N210 with this GRC diagram where I'm trying to upconvert a 1kHz sinewave.

I tried just upconverting the signal from the signal source to 2.5GHz. However, I keep getting the output signal at the frequency of the UHD:USRP Sink Block; this is, I'm not getting the sum of the baseband signal and the USRP signal as expected. What could be the reason?

500 kHz = 0.5 MHz = 0.0005 GHz.

You're providing a signal at +500 kHz, and then upconverting it to produce a signal at 2.5005 GHz. Are you sure that your measurement of the output frequency (and the USRP's oscillator) is precise enough to distinguish between 2.5000 GHz and 2.5005 GHz, absolute?

A way to tell if your signal generation is having any effect is to add modulation. This can be as simple as adding a GUI slider to control the frequency setting of the signal source, and moving it while you watch your spectrum analyzer. It's a lot easier to measure relative values than absolute ones.

• that, and also: the gain is probably 20 dB lower than intended. – Marcus Müller Oct 6 '20 at 8:41