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I've got, what is most likely the first version of the F5, plug in coil machine. The machine seems to work as it should until coins are in the +5" depth range. I have a test garden that has been undisturbed for 7+ years and regardless of settings or combination of settings the machine with the stock coil (concentric coil) is not able to detect a 6" dime with any regularity, no repeatable tones that would trigger me to dig.
A little more information is in order:
After carefully ground balancing the machine I set the gain to 50 and the threshold to +5 with no EMI or chatter. I swept over the two deepest coins in my test garden, which is a 6" dime and a 7" rivet but could only get an occasional repeatable tone in discrimination mode. Noticed the VDI numbers floating from 70 to 10. Switching to the all metal mode and the ID numbers hovered around 11 with an occasional 80 to 90 reading. Strange, I adjusted the gain up while leaving the threshold at +5, then when the chatter began I dropped the threshold to +3 and all was silent. Still could not get a repeatable or what I would call an audio that would trigger me to dig. So, not being satisfied with the progress I studied and played with many different gain, threshold and discrimination settings before turning the machine off and turning on my Eurotek pro with the 11" DD coil. The ET was able to detect each of the two targets with a repeatable high tone down to a sensitivity setting of 8. Next I turned off the ET and setting it with the F5 some 20' away I got my F75 LTD. The ground balance was almost exactly the same number as the F5. It too had no problem detecting the two targets with medium to high sensitivity settings. Both the ET and the F75 gave very clear, nice audio responses over the targets. So I pinpointed the exact location of the two targets and tried the F5 again and the same thing, no audio to speak of. Switched back to AM mode and the ID numbers seemed to stay in the iron range.
I believe there might be something wrong with the coil on the F5, but not sure of that (not a trouble shooter), but I did talk to Lupe at 1st Texas and he said it sounded like a harmonics problem with the coil (what ever that means). But one thing for sure is the F5 would report the two targets as mostly iron, that may be why I would only occasionally get a repeatable high tone or the second tone if I was using the 2 tone option. The F5 acted like the old iron wrap around issue that used to be a common problem with many detectors years ago. Only thing for sure is both of my other machines could detect both targets with no trouble. I have reason to believe, if the F5 was working correctly it should have had no problems detecting these targets.
Thoughts welcome
A little more information is in order:
After carefully ground balancing the machine I set the gain to 50 and the threshold to +5 with no EMI or chatter. I swept over the two deepest coins in my test garden, which is a 6" dime and a 7" rivet but could only get an occasional repeatable tone in discrimination mode. Noticed the VDI numbers floating from 70 to 10. Switching to the all metal mode and the ID numbers hovered around 11 with an occasional 80 to 90 reading. Strange, I adjusted the gain up while leaving the threshold at +5, then when the chatter began I dropped the threshold to +3 and all was silent. Still could not get a repeatable or what I would call an audio that would trigger me to dig. So, not being satisfied with the progress I studied and played with many different gain, threshold and discrimination settings before turning the machine off and turning on my Eurotek pro with the 11" DD coil. The ET was able to detect each of the two targets with a repeatable high tone down to a sensitivity setting of 8. Next I turned off the ET and setting it with the F5 some 20' away I got my F75 LTD. The ground balance was almost exactly the same number as the F5. It too had no problem detecting the two targets with medium to high sensitivity settings. Both the ET and the F75 gave very clear, nice audio responses over the targets. So I pinpointed the exact location of the two targets and tried the F5 again and the same thing, no audio to speak of. Switched back to AM mode and the ID numbers seemed to stay in the iron range.
I believe there might be something wrong with the coil on the F5, but not sure of that (not a trouble shooter), but I did talk to Lupe at 1st Texas and he said it sounded like a harmonics problem with the coil (what ever that means). But one thing for sure is the F5 would report the two targets as mostly iron, that may be why I would only occasionally get a repeatable high tone or the second tone if I was using the 2 tone option. The F5 acted like the old iron wrap around issue that used to be a common problem with many detectors years ago. Only thing for sure is both of my other machines could detect both targets with no trouble. I have reason to believe, if the F5 was working correctly it should have had no problems detecting these targets.
Thoughts welcome