[CamperBob2]

Only if it's strong enough to be obvious there's a signal there to begin with. The idea behind SS is to use more bandwidth than necessary, often much more, so that a much-worse SNR can be tolerated.

Many spread-spectrum applications such as GPS use signals that are well below the thermal noise floor by the time they're received. Those signals generally can't be detected without a known sequence to correlate them against.