F70 in DD SIZZLE mode

I didn't have a lot of time to detect, but I was going by Oakland and decided to take my F70 & the 11" DD with me as there's a park there I wanted to try. This particular park is right smack in the middle of the city, with skyscrapers all around it, yet I get ZERO EMI here, and previously was able to run fairly high sensitivity on the F70 (better then anywhere else, which is odd given its location).

At any rate I was able to run the sens at 95! I tried 99, but apparently I was pushing my luck as it was picking up a little ground noise even though it's only four increments higher (I assume it's also hitting the max range of the amp which probably is is prone to inject noise into the circuit?). About the highest I could get away with on the threshold was -2, with disc @ 5, 4H tones, nothing notched, and it ground balanced @ 64.

In a well pounded area I got an iffy signal, bounced all over but never into the lower iron or higher iron falsing range. Dug it and it was a 1940 wheatie. Another iffy signal turned out to be a pendant with a pair of parrots on it (love birds), but here's the bizarre one. Got a deeper signal, hitting high 70's low 80's but bouncing. Dug it, and found what appeared to be an old ceramic top to a bottle or something. Waved it passed the coil and it would sound off. It had dirt caked on it, so I figured there must've been some iron inside it. When I got home I rinsed it off and it actually appears to be made of white marble, and on the top it's acid etched (and barely legible) with a circle and inside the circle is a Victorian style monogram of HK, and going around the parameter of the outside of the circle it says "Hansen & Kamler - Oakland, CA".

After rinsing it off, it doesn't appear to have any iron, and no longer produces a response on the F70. Strange huh? I thought perhaps it originally had a metal retainer that rotted away, but there were no signs of such in the plug (no blood spots or visible bits of iron) and no rust spots on the marble piece. I know it was common place to use marble tops on medical implements, and am wondering if "HK" wasn originally a Pharmacy or such (google didn't return hits).

At any rate, a couple of interesting finds after an hour of hunting and the DD did well here. I've never been able to run with as high of sensitivity and threshold as here yet, so I hope to coax out some deep silver hiding (so far the only silver I've only managed to pull here was a 1910 Barber). It may be a good place to take the Sovereign with the Sunray S12 12.5" DD coil to hunt the deepies...hmmm. I'm also tempted to take the Coinstrike there with the 10.5" coil as it should do well with this tame soil and lack of EMI (which just kills the C$). It might sniff out some coins on edge with the 10.5" elliptical concentric, or some deeper stuff as well.

hh,
Brian

PS - Why does zinc so funky (moves around when pinpointing, and generally sounds cruddy if there's the slightest amount of decomposition ???



Edited 3 time(s). Last edit at 06/30/2009 08:10AM by Cal_cobra.

You may have been able to put Sens on '99'..... then swing the coil....and the EMI would have (most probably) mitigated.

Sometimes one side of a Zinc penny (left-side, right-side...... not obverse/reverse) will corrode....and cause the detector to respond a bit irregular.