In message , Mark

As for decrypting true digital encrypted transmissions, I don't believe there
is such an animal since you NEED the key. Without it, you're just guessing.
Perhaps this box rambles through keys in a trial and error mode until it picks
up a signal? Depending on the key size, this could take countless years to
accomplish.

Try doing a google search on "police tetra in the UK."
British police have recently gone from analogue FM to encrypted digital
and are no longer receivable by scanner users.
Where Britain goes today the Americans follow!!
--
Bill