I'm not as knowledgeable as a fella named Monte, but the way he explained it, it was due to the circuit design of the Compadre. There's no low-noise, high gain circuitry in the Compadre to alter the signal. That, as well as the ED-180 circuitry is why it is able to pick up a fine gold chain while others won't. So don't let anyone tell you that the Compadre is a weak Silver umax or other Tesoro. It is an entirely different circuit. It's hard to believe until you see it for yourself. I have an old Garrett bfo that will duplicate it's behaviour on gold chains WHILE rejecting paper clips and small nails and if it had the depth of the Compadre could probably be a fun detector. But the light weight, depth, etc. made me decide to go ahead and get one.