I've had a couple of them and begining to wish I'd kept mine. Anyway. I've never heard of one having to be calibrated. I keep hoping they will come out with one on a regular mount. You know, the old grab the rope and put it up/down. I just have too much trouble physically with the mount they use now. Maybe I should E-mail them and chew them out for not looking out after us old farts. LOL