The DeTeWe 8500 has DCS (Advanced Digital Code System). This allows radio traffic to be "encrypted" using 83 different codes. The participants in a group talk to each other and dial the same code. This makes it extremely unlikely that someone in the reception area uses the same channel and the same DCS. Since I activated the DCS, I have never heard a strange voice again.
But this has nothing to do with the scan function.

I can only recommend DeTeWe! Price-performance is top! Had foreign radio traffic on "my" channel once so far.

With the DeTeWe Outdoor 8500 and the right settings, this should not be a problem.
We have not had any strange radio calls so far.
I can highly recommend this device for this reasonable price.