Dave J. said:
Should be a good combo.
Every machine has its strengths and weaknesses. A site that's "hunted out" by one, leaves gobs of stuff behind for something else. What this means, is that if you're gonna search a site with two machines (or one machine set up two different ways), you want them as different as possible.
The TR has plenty of depth, a sampled discriminator, comes standard with 8 inch searchcoil, and has slow audio response. You'll probably rely to some extent on target ID to decide what to dig or not dig. That's in disc/ID mode.
You can also search in ground balanced all metals operation if you're willing to "find" everything. It's like having a whole different machine, and the trick is knowing what to do with that whole different machine. There's no straight answer to that, it depends on site conditions and on what works for you personally.
The TK4 doesn't have a lot of depth, but within its depth limits it's got a fast continuous-time discriminator. Putting a 4 inch searchcoil on it plays to its strengths in target separation and ability to reject flat iron.
You're set to clean house. When you're done, tell the Minelab guys you've already been there with BH's, don't waste their time.
Not knocking the Minelabs, but between a guy swinging BH's who knows what the heck he's doing, and a Minelab in the hands of the regular ignoramus user, the advantage goes to the guy with the BH's.
Good one Dave J.. But what about the guys that think they know their minelabs? 
