I would recommend you use a Shure model 444 or a Shure 444D. Run the "D" model in high impedance mode (it's switchable) , if you end up with the straight 444 it is high impedance only, 50K Ohms. Both of these will work and sound great with your classic Yaesu! Bud Garside, Owner Amateur Radio Service / ARS Sherwood Oregon, (503) 554-8831