F75SE Falsing at 3 and 4 tone

I noticed today while hunting in a trashy area that I cannot hunt with 3H or 3 or 4 tones without excessive falsing!! And this is with absolutely NO emi issue. I was hunting in a disc of 3 and a sensitivity of 99 in DE mode. It would start the EMI chatter in DP mode. But in 2F tones it wouldn't false. But if I clicked it up to 3 or 3H I would hear an internal hun or threshold commence. Then, I would sweep the ground and every sweep would cause Hi Tone falsing complete with hi numbers although a sweep in 2f revealed there was nothing but a few nails under the coil. In other words, trying to hunt in any TONE BUT 1, 1f, or 2F was next to impossible due to far too much falsing.
Question: Since I hear a threshold kick on when switching to 3 or 4 tones, are these tones somehow more sensitive than the much quieter running two tone??? Or has this post totally confused all who have tried to make sense of it. I did find a 1952 nickel today at a measured 9 inches!!!! In two tone. Which i wil likely hunt in from now on unless I am doing the ONE TONE and DISC 6 mode of unmasking.

If you were hunting a old site coal might be your Hi tone false problem , try a different site to determine if its a extenal problem.

Everything else seems on par with your F75 . My internal hum kicks in around 85 and the 3rd and 4 th tone do seem a little more sensitive than 2 tone.

Thanks for your reply Gman. This happens when my senitivity is alreay at 99. If I can run Dp mode at the location without EMI interference, I will, but for reasons of my example here, let's say that I am in Sens 99, Disc 1, Notch 1 (will notch even GO down to zero?), Tones @2F Mode: DE Successfully Groung Grabbed at 59 after repeated attempts just to make sure. I am sweeping happily along listening for the deep signals, watching the VDI screen. When all of a sudden I decide to switch to 3H, or 3, or 4 Tone. When I switch to either of these immediately an additional threshold hi pitched hum starts being heard. I switch back to 2F and it disappears. I switch back to the higher tones and it reappears. My question is: Is this significant. Are these "Higher Than 2F" tones more sensitive to targets due to the increased noise? And in addition, in ground that is not cluttered in 2F, starts acting like ground that is full of hi tone-mid tone clutter but I cannot isolate any of the sounds in the ground. In other words, at the higher tones falsing becomes a major problem. I cannot even hunt in these higher tones due to immediate fatigue of the auditory senses. Not so with 2F in the same ground. The iron tones are real and are caused by real iron and are repeatable as I circle the iron tone. Likewise the mid tone target sounds. Repeatable and diggible. In other words, almost zero falsing. Other than that the unit performs well. It will air test a dime to right under 14 inches with a real world sweep speed! I am pleased with the power. I guess that I will stay in 2F when detecting and hope that I won't miss deep coins.

I found the cause of the weird buzz when in 3 or 4 tone!!!! My coil plug wasn't all the way in because the retaining nut had come loose. I tightened it up and the weird buzz went away. Thank you all the same foryour reply Gman.

Thank goodness for simple fixes.