... so he was supposed to be "scanning" the police radio? If we pretend for a second that the potus is not fucking retarded, my first issue would be that whatever he's supposed to be scanning, he could be doing that from a lot further away.
Police radios are not usually encrypted so you could literally just scan for police radio with an ebay police scanner. There are internet radio stations broadcasting police radio from across the globe 24/7. If it is encrypted, cracking that would certainly be a lot more involved than waving a cell phone around.