Small Coil Mystery Solved?

[RLOH]

I read everyones advice and reset the f75 according to the manual. I didn't go back to the spot I was at yesterday, but went to a similar trashy park. I set the detector up exactly like yesterdays hunt and it worked perfectly. Ground balanced at 60 and the ID was dead on. I dug 22 coins with three being 6 or 7 inch deep wheat pennies. I did get a couple of one way high 80's and low 90's readings. These were one way signals that read in the high 60's range when checked from another angle. I dug them to verify what they were. All of these readings turned out to be wadded up aluminum foil. Where I hunted yesterday is a strange place. There is a huge coal fired generating plant less than a quarter mile away. I had one of the first Tesoro Tejons and if I was at the part of the park closest to the plant, I could not get the Tejon ground balanced. If I moved to the other side of the park, it was no problem. Also, I ground balance in the high 80's at this place. Yes, the coil plug is extremely tight and I always feel like I could snap the control box off the rod when removing the plug. I guess it is entirely possible that I did not have the plug completely seated. Thanks for all the advice and with everything working, I am happy with the small coil's performance. R.L.