Content provided by: FlexRadio Systems Engineering Not all sound cards have sufficient dynamic range nor do some properly support the Windows mixer controls. For proper operation it is important to use a sound card that has been certified to work with the SDR-1000. Use of sound cards other than those posted there are at the users own risk. A FlexRadio require an external sound card for one. Then, the wiring between the radio, external sound card, and the computer is not simply accomplished by acquiring and using a CAT cable either. By no means would I call the SDR-1000 a 'plug and play' deal.