In my boyhood I was familiar with a number of biplanes where the airspeed sensor was a flat plate on a coil spring mounted against a scale on the interplane struts. However icing would change the drag coefficient and might even lock up the spring
Any blade antenna produces drag proportionate to airspeed that a force transducer could convert into knots. Whether the antenna people provide ice resistant coatings or proper heating elements is another question, but at least such a sensor would not be vulnerable to clogging. To be useful such a sensor would need to provide usable indications at altitude where the available speed range can be quite narrow.