I paid around $580 for my F70 with the Fisher 11" DD coil -- I had to send this unit into Fisher after two months of use because of the constant chatter -- (was I sold a second??) -- I will not tell you who I bought it from this may not have been their fault at all? Fisher was very helpful -- my machine was chattering constant, just could not quiet it down and the Fisher Tech told me to call him the next time I went out to hunt. After many infield conversations with the Fisher Tech he said to send it in -- he could hear the chatter for himself and with me following this instructions for settings in attempts to get this to stop -- I was still finding targets, the target hits were sharper and loader than the chatter, so I was finding things but talk about the ???? torture it was a relief to stop searching. I sent it in and about a week later they sent it back to me with a brand new 11"DD attached and they had opened up the F70 case and replaced the battery compartment and springs -- hum, not sure what that would have to do with the problem? When I got this baby back it was a whole new experience, and setting up Mudpuppy's advised settings, this time, produced a fantastic run for the last 8 months of 2013. So, if you are having, still, such a problem then I would suggest getting a Fisher Tech in the field with you, via cell phone, hearing is believing. But first try the following settings, thank Mudpuppy, and see if this helps, if not then get on the horn with Fisher. Disc 18, Sens 60, dE, Thres -3, Tone 3H and no Notching. This machine has never suffered from EMI interference -- there are a lot of power lines in my town and power boxes all over the parks -- I have searched and found targets right up next to these massive power boxes in their cages (hum, maybe the metal, screen, chain linked protective boxes are acting like some kind of shield?). At first all the chatter was being blamed on EMI but this proved not to be the case, something else going on. Fisher, by replacing the DD coil is indirectly blaming the coil, but why did they open up the case? The battery compartment looked okay to me, but what do I know -- It is definitely a different machine and a different experience. Hope this helps someone. P.S I reset my Thres to -2 because, according to a test chart provide by another member the -2 settings in these air tests were nearly identical as the +2 -- this means the -2 Thres setting is better than -1 and 0 and +1 and verily nearly as good +2 all the way up to the +7 setting. Looking at this test chart it would appear we are talking about differences of 1/2". The +6 setting, for example, tested out as inferior to the -2 setting (that is minus two) -- I am sorry I do not remember who did this test or supplied this air test chart -- :blush: Maybe someone else remembers the member that posted the chart and can redirect us, thanks. Dan