R7 K-band settings for occasional small-town threats?

I see about 85% Ka threats and 15% K-band threats. The K-band is only for the occasional small town cop or Sherrif around here. What setting should I be using in this situation? K filter or K-narrow on?

I turned on TSF and the detector got a lot quieter. No speed cameras I was aware of, so what was causing all the false alerts prior to using TSF? Active cruise and parking systems from other vehicles?