I know there is a lot of build your own metal detector info out there. However, I would like some input on changing coil design. Typically, the depth of the EMF is near the diameter of the coil...the very bulky coil. I have had great success gold prospecting by looking where others don't. namely crevices well above current water levels, water laid gravel benches on the sides of bone dry hills etc. My quarry would be: can a substantial EMF be generated vertically? Say, creating a coil that is long and narrow that would direct the EMF to a point 1/4" - 3/8" in diameter? The purpose would be for probing deep cracks above and below water level. There was a detector on the market many years ago...it could pin point very small gold nuggets, however it had virtually no depth, you had to almost be touching the metal to get a reading. And if coils have to be bulky, is there a way to concentrate or direct the EMF in a vertical depth orientation? thanks, plumber.