Just your basic silicon signal diode, equiv 1N4148.
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_36311_-1
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_36038_-1
Without seeing the schematic, the bet is that ultrasonic windmeter is not using a UHF diode.