Erratic threshold

[bb]

I am a newbie to detecting and have a DFX 300 with an additional dd2 10" coil. I have been getting very erratic readings and have been reading the forums to try to resolve the problem. My threshold is not a good steady hum even when holding the DFX in the air. As I change between the stock programs the hum breaks up more in some programs than others. The problem is more noticable with the 12" coil than with the dd2. If I have instability in the air, I would assume that my ground readings are not going to be any better.
I also read about using the DC Phase to check for ground mineralization. I tried setting DC Phase ON, place the coil on the ground, pull the trigger and watch my VDI go nuts. I get constantly changing numbers from both extremes of the scale.
I have lowered AC Sensitivity down to 50 and it had no effect on the threshold sounds or the DC Phase readings. I also did the reset by removing the battery and restarting.
In addition to having to listen to the erratic threshold, I am concerned that I may be missing targets due to instability. I recently hunted the front yard of an early 1800's farm house and was very disappointed in in not finding anything other than some clad coins and a lot of junk. According to the owners, whose family has owned the property for at least 3 generations, I am the first person to hunt the property. Needless to say, I had great expectations.
I would appreciate some suggestions from you seasoned experts.

 

[nw1886]

Things that could still be causing this are strong EMI from electric fences, military installations, overhead and underground power, salt/magnetic debris under coil covers.... Lesser chance: Bad coils, bad coil wire connector at box (very unlikely but...?). Others will chime in too. Good luck.

 

[Larry (IL)]

Is the DFX new or used? It could need service. Is it in warranty? I would use the coins program with the 10"DD and be sure to ground balance TWICE back to back before hunting. If it still acts badly, you either have an EMI source or the DFX needs calibration. EMI can be an invisible dog fence, power lines, transformer, electric fence and the like. Try the Coins program in another spot and see if the helps.

 

[bb]

Larry,
It is a new, about 2 months old.
I removed and cleaned the coil covers and tested without the covers. I drove to 4 sites within about 5-6 miles of home and still have the pretty much the same issues. The Coin/Jewelry mode does have a more steady threshold hum than the Relic mode. But even where the threshold sounded good, I still got DC Phase readings from one end of the scale to the other, when pulling the trigger and holding the coil steady against the ground. It might start out with negative numbers and climb towards the high numbers and bounce around there and then move to the positive side. It will continue to change like that as long as I hold the trigger.

BB

 

[Larry (IL)]

My best guess is the DFX has an electrical grounding problem. An exchange with your dealer or a call to Todd at service in the factory should solve your problem. Either way, I think a new detector should solve the problem. A bad loop has been know to cause that problem, but both loops being bad are not likely and that leaves the DFX having the problem. IMHO.

Factory 1-541-367-6121

 

[bb]

I live in northern VA and suspect that the soil may have a high iron content. Would that account for the erratic DC Phase, or should it just give me a number indicating high mineralization?

BB

 

[bb]

Thanks Larry,
I will call the dealer and see what we can work out.

BB

 

[Larry (IL)]

If you are holding the loop still, the DC phase should not vary much at all.