URL and params with %E4

I got an url I like
http://localhost:3000/article?text?n�sta

When I read the parameter params[:text] I only get näa. It deletes the
two characters after %E4.

In my log i can see the parameter:
Parameters: {“text”=>“n?sta”…

The length of chars is only 3
params[:text].chars().length

The length of the parameter is 4
params[:text].length

The Chars is:
params[:sms].length.times

CHARn=0=n
CHARn=1=?
CHARn=2=?
CHARn=3=a

The chars for chars():
params[:sms].chars().length.times

CHARn=0=n
CHARn=1=?
CHARn=2=?

Any suggestions how I should solve this?