The attached mission demonstrates the 1Hz IQ Signal Generator block resolution. Please notice that it needs some time to generate the first spectrum since the dwell time (Low Sample Rate) of the IQ Demodulator is quite high. For an even higher resolution change the sample rate accordingly (e.g. from 100kHz to 10kHz). You might also want to reduce the sample rate of the IQ Signal generator block itself. In this case you can use a smaller FFT (without the need of the 1M FFT key).