Goals from Sol Campbell and John Utaka downed the home side, who saw defender Ibrahima Sonko sent off in only the third minute.
Pompey now have the best record on the road, jointly with Chelsea, but have been struggling in front of their own fans.
Redknapp said: "That's seven wins out of eight away from home - it's amazing. No-one has won as many games away as we have.
"If we had won our fair share of home games we would sitting on the top of the league now.
"I'm delighted with what we have done."
Redknapp was almost claiming an assist for the Utaka goal, which saw the Nigerian outpace the home side's illness-hit defender Nicky Shorey.
He explained: "He has pace to burn but he wouldn't have run for the goal if I hadn't been standing a yard away from him.
"I said to him 'please John, run behind the full-back' and in the end he did."
Reading manager Steve Coppell refused to blame Sonko for conceding his third penalty in four matches and goalkeeper Marcus Hahnemann for gifting Pompey their opener by fumbling a simple cross.
He said: "It was poor defending but I don't do my dirty washing in public. He has been magnificent for this club and if he makes mistakes all of them are genuine.
"And I can count the mistakes Marcus has made on the fingers of one hand. I just took for granted he would take that cross.
"You can't judge them on 85 minutes with 10 men. The 10 men I thought were magnificent. They will sleep well tonight and I could only thank them at the end of the game."