How much does it impact on the performance of the antenna if stainless steel is used a part of the enclosure?

[Ethan]

we are considering using .005" thick stainless steel to provide better bridging effect across the opening on the board for the battery. This will provide more strength to the final assembly. The one question is the performance of the antenna and if the stainless steel panel will impact the antenna strength. The antennas are the same as one in Thingy: 91.

Could you please advise me?

[Denis Rustak]

It's going to depend heavily on the exact arrangement of things (size and placement of the metal, type of antenna). 

That said, you typically can't throw metal into an existing design without drastically degrading the antenna unless it's part of the ground plane (and even there it will likely affect the radiation pattern).  Multilayer or high-dielectric antennas, like chip antennas, are especially touchy with nearby metal.

It can be done, but it has to be designed in.

[haakonsh]

This is true, you can't know for certain without testing the antenna performance in a lab. You can get close with a proper simulation, but that is quite expensive. 

I suggest you start by sending opening a Private ticket and send us your schematics, layout, and a 3d rendering of your enclosure that shows the position of the metal piece with respect to the antenna. We can make an educated guess whether it's feasible or not.