In my assignment I am provided with a recording of a radio signal that was supposedly done in the AM spectrum with a USRP, and I am told to process it in various ways with GNURadio. However, the assignment makes a statement about the recorded signal that I have slight difficulty understanding.
The assignment says that the signal was recorded with the USRP set to 710 kHz, yet it also says that the recording was sampled at 256 kHz, and that the 0 kHz component of the recording actually corresponds to 710 kHz in the original signal.
My understanding is that the only way for this to be the case is that the signal was recorded with a frequency well above 710 kHz, then the frequencies were translated so that the 710 kHz component was shifted to 0 kHz, and finally sampled at 256 kHz. Is my understanding correct?
In relation to that, what does it mean for a USRP to be set to a particular frequency, if the recorded signal seems to contain frequencies several tens of kHz above and below that frequency?