I am studying on some signals which occupy more than 20 MHz, maybe 21 MHz, e.g..
I was suggested setting a RF span bandwidth around 10.5 MHz, as I was told somewhere. However I found some spectrum difference if I set the RF span into 21 MHz than 10.5 MHz in my experiment.
If I set it to 21 MHz, the whole interested spectrum could be shown by voltage_0 or voltage_1, only one channel is enough.
But if I set it to 10.5MHz, the spectrum could be shown by voltage_0-voltage_1 choice, which needs two channel, and the obtained spectrums seem different.
What is the mystery?