I'm not tech. but I have the YO-301 hooked up to my FT-990 and it works = fine. I use a jumper from the" AF out" on the FT-990 to the "V amp in" = on the back of the YO-301 to monitor RX. Maybe this helps?? --- StripMime Report -- processed MIME parts --- multipart/alternative text/plain (text body -- kept) text/html ---