Pompey have signed goalkeeper Brian Murphy on a deal until January.
The 32-year-old – who will wear the number 24 shirt – has been training with the Blues for the past few weeks and played in the friendly victory over Woking.
He said: “I’ve enjoyed getting sharp here and now I’m delighted that we’ve been able to get the deal over the line.
“Motivation certainly won’t be difficult here – there are not any other teams in this league that will get 17,000 for home games.
“Everyone knows where Pompey were a short while ago and where we are now, so it’s up to the players to rise to the challenge.”
The Irish stopper came through the ranks at Manchester City and moved on to play for Swansea, Bohemians, Ipswich and QPR.