McKenna was speaking after Friday's friendly win against Derby.
McKenna said: “I don’t think there’s anything imminent to update on, to be honest. The club are working really hard, I’m working really hard, everyone’s working really hard to make additions to the squad.
“We would like, in an ideal world, to have been a couple of additions further along by now, but we are where we are.
“It’s a challenging market, there’s lots of challenges in there and I think there’s a balance to be found between getting in players who can help us as quickly as possible but also getting in the right players who are going to help us over the course of the season and over the course of the next 10 months, not just over the next 10 days.
“I think it’s important that we have and we continue to make decisions that are right for the bigger picture for the season and for the years ahead and we’re going to look to try and do that while also strengthening the team as prominently as we can.”