There are no hard and fast rules regarding the ratio of technical to managerial skills. Any PM should have a good balance in three functional areas - business management, technology and behaviour.

The important point to note here is that any PM should have a clear and unambiguous understanding of his/her roles and responsibilities and know the boundaries of the job and not step on anyone else's shoes.

As a PMP myself, I believe that a good foundation of technical skills is a mandate for any manager. The PMI also recommends that the best and most effective form of power a person could weild in any organization is 'Expert power', which means that you are an expert in your knowledge area. For instance, if you are going to lead a team of engineers and if you are an recognized engineer in your field, then your team will trust and respect you and it would be easy for you to lead them.