Is there a way to make an animated blurred mask?

I want to use an animated mask with blurred edges ( feathered ) so that when it moves over the masked image, it has a blur.

In example a circle getting bigger to reveal the image under but with feathered edges around the circle.
I have tried using gradients in the animated mask, but it still shows up as solid circle. Any help would be greatly appreciated.

Thanks in advance.

Found answers from a great dude.
May help others.