This is one of the major pitfalls of phone, skype, video, etc... interviews.
Did you have the interview scheduled at a time that you both agreed on, or did the PSM call you at a time that wasn't confirmed? If the timing wasn't confirmed, I'd perhaps drop a quick note apologizing for the poor connection and offer (but don't ask him to) to schedule a second call if he'd like you to clarify any of your responses that may have cut out.
Chances are if he didn't understand your responses or needed further clarification, he would have asked during the call - so you may be OK.
Here's a
quick and dirty five point blog post that can help with phone interviews in the future. If possible, do your interviews on a land line. If a land line isn't possible, then make sure you're in a location that you know from previous experience has good cell reception.
If you did agree to the time beforehand and you were in a position with poor reception, then unfortunately that's on you and there probably isn't a whole lot you can do. If you agreed that he'd call you at 4:00pm, then it's on you to be ready for the call at 4:00pm. Being ready includes many things, and certainly includes a reliable phone connection. I don't mean to sound bleak, and it's certainly possible others here will have some better advice on the subject. Good luck, and I hope the challenges with the connection don't affect your ability to get this job!
EDIT: Here's another bit from
Lifehacker on phone interviews. Can't recommend this blog enough!