I would monitor the Jefferson County Public Services Mot II system. Also the tower frequency at the airport. Also, not sure what direction he will be coming from but Atlanta, Memphis, Houston, or Jacksonville Centers alsao. RR in Jefferson Cty Conventrional has listings for those frequencies. State Police will most likely get into the act, so what ever state frequencies are used in Birmingham. Probably comms with in the Secret Service will be encrypted. But you should have a good time looking for Potus comms. Security provided by locals sources should be in the clear. Any talk group for Birmingham could be used but Iwould guess Events, or Tac or Tac Command.