Just to cover the DEA, since they're well known, they'll mostly be here, when not using someone else's system, or Nextel:
F1) 418.625 (R)
F2) 418.900 (R)
F3) 418.750 (S)
F4) 418.675 (S)
F5) 418.825 (R)
F6) 418.950 (R)
They have others, but these are the main ones. Mostly, they only use this system during actual surveillances, on the two simplex channels, but you never know. Some areas are 100% DES encrypted, some are casual about encryption.