The P-SB7 Spirit Box® utilizes a milli-second adjustable Forward or Reverse frequency "sweep" technique coupled with a proprietary high frequency synthetic noise or "white noise" distributed between frequency steps.
We are using a new noise cancellation circuit that we believe is a great improvement. We added noise reduction on the FM channel and we brought back the AM. The FM and AM are balanced equally so both can be heard. The refinements of the new version are made specifically into the AM bandwidth. You will hear more radio detail in the AM bandwidth, it will be clearer m during the sweep session.