Strange target response

I went hunting (using my F75) at a local park Tuesday afternoon. The area where I was hunting was an area I had covered very good in the past 4 years with both a Vaquero and Tejon machines.

Right off I noticed the machine was very unstable or perhaps I should say a lot of ground noise ( a lot of pops, cracks etc.) I chose to run the machine a little hot regardless of the extra noise. Not expecting to find much was a mistake, I should have turned the sensitivity down until it was quite, but didn't. In an area where I had found a silver ring last year I got a very loud double beep. From past experiences I knew it could be two targets a few inches apart, surface metal or a coin on edge. Taking Tom's advice I started rotating around the target and about a 90 degrees turn the target completely disappeared, yes not a single sound, no pop, crackel or static. Continuing to rotate the target came back. From past digs I had guessed the target was a coin on edge, and I was right, because about 2" down was a nice 1951 wheat penny on edge. By Tom's compilations I would be assured that there was other target close to where I dug the penny. Thanks Tom for the reminder. That's why it's so important to grid off an area and swing in a different direction every now and then.
Looking forward to watching the DVD soon.

Good 'catch'. This occurence happens more than you would expect.