I realize the conversion rate could be lower, but why not put this CTA in a non-pop-up form at the end of the article? If I really enjoyed it, that seems like the point where I'd be on board with signing up.
Your metrics may show that you get 0.2% signups with this method rather than 0.15%, but they likely don't show the much larger number of people who won't be coming back to your skeevy site, ever.