Jump to content

Looking For Advice On Detector...


Recommended Posts

According to legend, in a creek not too far from home, there are two gold bars from a stage robbery. Typical bars in these cases were 125 lbs, and would be about 8 x 16 x 3". I'm going to build a small raft, with a detector mounted on it. Said raft will be controllable by me, so it can be caused to sweep back and forth across the width of the creek as I wade behind it. I'd probably be 10-12' behind. because of barbed wire, and other iron trash, I need really good iron discrimination, and the size of the target means I don't need super sensitivity. A large coil would be a help, as would auto ground tracking. Wireless headphones would be a big help, assumin they can reach that 10-12' I'll be behind the detector. Also I'd need the coil to be waterproof to 24", Though I'm not planning on having the coil that deep. The detector being at least water-resistant would be a help. I'm thinking a lower frequency VLF of some sort, for depth, and will probably be buying on the used market as I'm happy with my current fleet of detectors, except for this specialized task. I'm looking for suggestions from you hotshots, and appreciate the help. I guess it doesn't need to be said that I'd like to keep the cost as low as possible.

Jim

  • Like 1
Link to comment
Share on other sites


First, I did a quick calc and the size bar you indicated would weigh 121 kg (267 lb) if pure gold.  That size bar would have to have a specific gravity of about 9 (right around copper) to weigh 125 lb.  So even accounting for less than pure gold (e.g. if someone just melted a bunch of nuggets and/or fine gold) it would still be heavier than that.

You didn't say how deep you expect the gold to be, other than you want the coil to be able to be submersible to 24".

Would auto tracking work at the presumably slow speeds you will be moving this raft?  And would the detector be required to run in non-motion all metal -- e.g. what is typically pinpoint mode on most IB/VLF's?

I'm not great on suggestions but hopefully my above questions/concerns will help you refine your requirements.

  • Like 3
Link to comment
Share on other sites

I'm unaware of any two box detectors that are waterproof, so, I would hesitate to use one in a river. One dunk and they're history. If the gold bars are not too deep, I would consider using an Excalibur or CTX with the biggest coil available. It would be pretty tough to modify an Excal with wireless headphones, but, the CTX shouldn't be much of a problem. Both of these choices have good iron I.D. and will go fairly deep for their intended use. If the target is 3+ feet deep, you would need something different, but, finding something that goes deeper, has discrimination, and waterproof might be a challenge.

Link to comment
Share on other sites

2 hours ago, Steve Herschbach said:

Might consider a Gemini 3 or TM-808 in a raft with no metal for the main hunt. A two box will ignore small targets and only get the biggies, might be just what you need.

Thanks, Steve! I'm considering that, but the lack of water resistance worries me. Whatever can go wrong, will go wrong...LOL But, you're right...the other attributes are hard to beat for this use. And, I've already got TM808.

Jim

  • Like 1
Link to comment
Share on other sites

Do the 3m x 3m pi frames go deeper? Wondering if those would be easier to mount on a raft.

Link to comment
Share on other sites

1 hour ago, cudamark said:

I'm unaware of any two box detectors that are waterproof, so, I would hesitate to use one in a river. One dunk and they're history. If the gold bars are not too deep, I would consider using an Excalibur or CTX with the biggest coil available. It would be pretty tough to modify an Excal with wireless headphones, but, the CTX shouldn't be much of a problem. Both of these choices have good iron I.D. and will go fairly deep for their intended use. If the target is 3+ feet deep, you would need something different, but, finding something that goes deeper, has discrimination, and waterproof might be a challenge.

Thank you, Cudamark. I'm thinking of the AT Max, sorta.  But, wish it had larger coils. I may just go with Steve's suggestion, and make a watertight bag to go over the entire TM808, and make an extension for the headphone cable. I've got a lead bar the exact size of the assumed gold bars, and the 808 sees it at 33", which is about as good as it gets...but no discrimination, and that might mean a whole bunch of under water digging, which would be a deal-killer. I may be over-thinking the need for discrimination, however. I'm also thinking of the DFX with a 14" coil. In Prospect mode it sees the lead bar at 30", and I could set it up to discriminate, even in prospect mode, I think.

Jim

Jim

Link to comment
Share on other sites

1 hour ago, kac said:

Do the 3m x 3m pi frames go deeper? Wondering if those would be easier to mount on a raft.

I've got a Delta Pulse with a 1m x 1m coil, but no discrimination. On iron it's better than the TM808, but not as good on the lead test bar....probably because of the lower frequency.

Jim

  • Like 1
Link to comment
Share on other sites

Nel Big works on the AT Pro and Max and does go pretty deep. I have picked up cans at the beach in the dry/damp sand in the 3' mark, lobster traps further. I could try to test the big on how far it can sense big metal, think I have some lead bars to see.

Link to comment
Share on other sites

Quickie air test between my Mars Tiger 10x13 and Nel Big 17x15 with a 2 lb lead ingot. Tone breaks from high to low 19" on the Tiger and 24" on the Big. Tone carries to to medium then nothing not much further.

I do have a lot of emi so guessing in the water you may get better performance than that and if on the Max much more depth.

The Nel Big can also double up as an anchor in case you wanted to have lunch out in the river and not lose your place.

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...