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Date Posted: 11:32:24 05/03/02 Fri
Author: Steve Herschbach
Subject: Underwater Fisher Gold Bug 2

Hi Everyone,

I've wanted an underwater nugget detector for years. I've done lots of gold dredging, and always wished I had a compact little detector I could use to check the bottom and sides of my excavation before backfilling it. Like most dredgers I always wonder if there is a nugget lurking just another inch into the material.

I've also done lots of underwater detecting, mostly freshwater, for coins and jewelry. I've used the Fisher 1280X, White's Surfmaster II, Surf PI, Tesoro Tiger Shark, and just got a Fisher CZ-20 for this summer. These are all good machines, but they really are not made for tiny gold. The Tiger Shark is probably the best for small gold in fresh water, as it has a ground balance and can use optional smaller coils. But it still lacks the edge of the nugget detectors. I've always wondered what kind of earrrings and thin gold chains an underwater nugget detector would find.

I floated the idea this winter of Tesoro building an underwater Lobo. The Lobo with it's automatic ground balance and the existing Shark housings would seem a easy experiment for Tesoro. Lots of people liked the idea of a environmentally protected Lobo.

But it will probably never happen. Anyway, I already have a Fisher Gold Bug 2, and so I built a cheap little underwater housing for it. The key here being cheap and easy... I just want to see if this idea has any merit before getting too carried away!

The Gold Bug 2 is a good candidate due to it's small size. Pelican makes a watertight case that just fits the Gold Bug 2, and they have larger cases of all sizes. I got the smallest model 1120E case online at casesbypelican.com for only $13.25 plus postage.

I bought a set of underwater headphones from Fisher and a spare 10" coil for the Gold Bug 2. I considered using the 6.5" coil but decided the 10" would be better for general use. The 6.5" would probably be better if the unit was going to be just for underwater bedrock sniping.

I cut the connectors off the coil and headphones and ran the cords through holes I drilled into the case. The cords were then permanantly sealed into the case with E6000, which is made for sealing underwater electrical cables. Keene dealers carry it.


Case with headphones and coil attached

The hard part for me was putting the connectors back on. I had not taken the length of the coil connector into account when measuring the case, and so had to cut the coil connector down and make it into a 90 degree elbow. The next larger case size would have eliminated this need to squeeze things in, but I like the smaller end product here.


Closeup of case and connectors

So, with everything done, all I have to do is drop the control box into the case and hook up the connectors:


Control box in case

The downside to being cheap and easy is I must turn on the detector, tune it up including ground balance, and then shut the case to use it. As the GB2 is a manual ground balance unit this will be very unsatisfactory for areas with varying mineralization. In my area I am lucky to have pretty easy ground, and so will be able to get away with this. It is the main reason I think the Lobo would be better if someone wants to try this, as it will stay properly ground balanced.


Finished product ready to detect

I am going to put the box in a small rucksack on my back. Headphones on my head with hood (full drysuit here in Alaska) and use the coil with just the plastic isolator rod as a handle.

I'm going to try several different experiments. First, underwater nugget detecting in a trash rich environment. Tomorrow I plan on heading down to Crow Creek Mine south of Anchorage and sniping the bedrock unerwater. Lots of nails and other iron trash, so I'll tune the unit up and run it in all metal and try for nuggets, plus dig iron spots looking for the gold that usually accumulates with the nails.

If the iron trash proves too annoying, I'll try running in iron id mode. This may be better for underwater use anyway, as it is a silent search mode and gives a sharp signal that will be easier to hear underwater.

I have another creek I want to try where trash will not be a problem, and all metal will be the way to go.

Finally, after the lakes melt off soon, I want to try the unit on the swimming holes and see if I can find any small gold earring studs that my gut tells me I've been missing with other units.

I know my unit is pretty low tech, but thought I'd share the idea here for those of you like me who are not really up to trying to build a housing with actual underwater controls. But mainly I will know in a few weeks of trying wheter the idea is any good at all. I'll report back here on my finds (or lack of finds) soon.

Steve Herschbach
Steve's Mining Journal

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