I’v e been looking around for some really solid advice to put into a post and what seems to come to mind is to recognize that a detector does not “punch down” through the ground to detect metal.  What it does is to separate ground and interference from metal.  When you do a lot of pulse hunting it becomes clear that no machine is invincible–all detectors lose depth under certain conditions.  Point being don’t expect too much from any VLF.  A good demo is to run a VLF near a known source of interference–like a furnace or TV.  Notice how when you increase the Sensitivity–target signals don’t disappear–they get “flatter” –that is–they go into the background and become harder to acquire.  This is what happens in the field.  What will get you more targets is to work with a moderate Sensitivity level and a slower sweep speed.  This is what will allow you to go into “prime ” ground behind other hunters and make finds.  With a VLF–try basing your settings on how the unit stabilizes in all metal mode–this is very telling–where you have “lilting” sounds or “nulls”–this performance loss will be even more pronounced in Discriminate–whether you can hear it or not.  With these multi frequency machines–there is such a bias towards stability that they are capable of loosing depth but still having a smooth threshold.  With a pulse you hear these threshold changes.  A pulse teaches the tuning and coil control needed to get performance from any detector.  Pulse hunting teaches you the reality of interference–and just how much of an effect it has.  The more sophisticated many of these detectors get–the less aware we are of just what we are missing.   Unfortunately–there’s no such thing as an “idiotproof” detector–conditions always dictate.   If any of you VLF hunters have the chance to borrow a pulse–try it–a real eye opener.  Another thing that’s worked well for me with VLF machines is not to be afraid to put in a reject block around “zero.”  This will reduce the interference from targets in the ground that fall on both sides of “zero”–making for cleaner assignment of responses.  The Sensitivity you run will be more usable–and you can set it higher with out so much of the kinds of problems described above.  It will reduce “cross-feeds” making for more stable performance.