Hi Brian, data sheet here   https://zl2bkc.files.wordpress.com/2013/01/sm3437.pdf  I have a 50W version and a couple of 20W - I have fired them all up and they all work fine - the 50 is now working with a DB6NT driving it. They are very high on gain so you will have to get the drive down to 0.5mW,   Graham G3VKV