F4 Double DD coil and Dankowski DVD

[gambler13]

Don't know how many of you are familiar with the Dankowski DVD or the F4 but maybe you can compare it your machine using a DD coil. In his test garden, sweeping over a dime, he gets clear crisp repeating high tones but he's using a round coil. If I take a dime, place it on top of the ground, where there is no other signal present, sweep my F4 with the DD coil over the dime, I get high and low tones, ID jumps all over the place, and digital scale jumps around too. Should that be happening? If I take my BHQDII with a 8" round coil, I get clear repeating high tones, and ID of dime. I will try my BH's 8" round coil on my F4 and see what the F4 shows then as well as put the DD coil on the BH and check that also.

 

[gambler13]

Can't believe that in a Fisher F Series forum, nobody replies to a Fisher F series question.

 

[Dave J.]

Gambler13, forum denizens were probably slow to reply because you didn't provide enough information to diagnose the problem.

DD's are different from concentrics. They don't like to ID close-up targets and they are more susceptible to electrical interference than a similarly sized concentric. Despite these disadvantages, DD's have compensating advantages and for this reason we generally prefer them in our newer higher performance products. In fact some of our newer products are designed to work with DD's only.

If you are getting screwy ID's with the searchcoil within 2 inches of the ground surface with the test target laying on the surface, you need to back off.

If you are getting screwy ID's with the searchcoil lofted 4-7 inches above the surface, you are probably getting electrical interference and need to turn down the sensitivity a little.

Out on the detection fringe you can expect a metal detector to give jumpy ID's regardless of what kind of searchcoil.

--Dave J.

 

[rick in mi]

Good reply Dave. My f4 does the same thing,but I use it to my advantage,its just telling me the target is close to or on the surface.