I have an USRP N320 SDR and I have an issue with 3 MHz-450 MHz band center frequency value. When I have a signal between 450 MHz and 6 GHz, I can see the actual frequency value of the signal even if I slide the center frequency but below 450 MHz, the signal is shifted negatively when I slide the center frequency. Is there any reason and solution for this issue? Any help?
As you can see in Figure 1, the FM radio signals are correctly seen when I set the Rx Tune Frequency to 100 MHz.
1
But when I slide the Rx Tune Frequency to 110, 120,130 and 140 MHz, the FM radio signals' frequency values are also shifted. As you can see in Figure 2, 3 ,4 and 5.
2
3
4
5
Addition:
The main picture of the blocks and parameters of USRP source are below figures.
Blocks
USRP Source 1
USRP Source 2
USRP Source 3
Also I figured out that when I applied below 450 MHz, for example 100 MHz signal and shifted center frequency with an amount, it shifts the signal double time inverse. I might not explain well but below figures does.
100MHz Signal at 100 MHZ center frequency
100MHz Signal at 95 MHz Center frequency but appeared at 90 MHz
100MHz Signal at 110 MHz Center frequency but appeared at 120MHz
But When I applied a signal above 450 MHz, for example 2 GHz, it does work properly. As you can see in figure below.
2 GHz given signal can correctly seen in any other center frequency
