I have done a lot of research. If you get the 563 manual from the Tentec site it says driver bias 50 ma and PA 500 MA increase. Also my friend Garry Greene who worked with me at tentec says. Garry Green from TenTec for the Bias adjustment was an idling current of 50mA for the driver and 500mA for the final PA stage Hope this helps everyone Gary K4MT