Steve M. Taylor wrote:

Can anyone point to a good resource on TUNING digital control loops?

Steve,
A good reference site telling how to tune digital phase lock loops was in QST magazine entitled "A GPS-Based Frequency Standard" July 1998. The web address is http://www.arrl.org/members-o...807037.pdf

The above site requires you to be a member of ARRL but most libraries carry the qst magazine (the article was featured in that magazine) in their serial section

The article tells of the problems you will encounter while trying to attain lock. There is a lot of experience in the article and might be what you are looking for.

Good luck,

Charles Bannister