home brew coils for BH

[diamondjim]

I'm building some crazy coils for my old school Rediculous Shack BH circa 1992, just to see what's possible. It wasn't a bad machine and did find plenty of silver...but I always felt like the stock 8" coil (long since dead and vanished) was missing deeper stuff.

What I've got at the moment is essentially a home made bigfoot coil that actually works...but gets poor depth so far, even though the target ID still locks perfectly. The poor depth is a combination of two issues I think, 1) I didn't have enough wire to wind the Tx coil I had planned for and 2) I don't actually know what frequency the BH runs on. At the moment coil is tuned to 6.59 kHz...White's freq...the BH is only barely stable in all metal, have to keep retuning. This first prototype was just a "proof of concept" platform...I've never seen inside a real bigfoot coil...this is just my guess at how it works...and surprisingly it actually does work.

Anyone know the freq of the old BH's

Anyone interested in building whacko coils for BH's?

I have this picture in my mind of going to some of the OLD parks around here...the ones hit daily by clad hunters with thousand dollar machines...with a crazy ancient BH and start pulling deep, deep silver. My OTHER machine has proven there are deep coins in the 8 to 10 inch range...pennies. When I get down there always the same thing, a huge green ball...halo effect. I know there are dimes down that deep that are simply escaping me and everyone else. Don't really want to risk experimental coils on the other machine I depend on and can't afford to replace...so time to reinvent the BH.

So, if anyone's interested I'll keep you posted on the bigfoot for bounty hunter project. (Actually calling mine the warp bubble coil for now, til I find a better name)

Working now on the 2nd prototype, with a max depth of 10 inches and sweep of 12 inches. Just a stepping stone towards an amazing coil idea that holds the promise of silver dime at 20 inches. While that IS excessive, you'd never, ever have worry about anything escaping.

Any info on stock BH coils helpfull to get my stuff tuned up.

 

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[MD Dog]

See now ya got me interested. I've had the same dream. I've got alot of other machines and have had about the same results as I have with my Mark IV. For $130.00 or less we could maybe take the basic design and tweak it to be the super machine that everyone wants but at a fraction of the cost. Before one of you brand loyal jerks starts mouthing off about how deep your machine can go, I don't care. Beside I've probably already tried your machine and discouted it and such statements as pure B.S. Why anyone would want to dig 12 or 20 inches is beyond me unless you could be really sure of what your diggin for. So yeah lets see what you come up with and I'll see what info I can find for you.

 

[diamondjim]

Yeah, I know those depths seem excessive but could you imagine all the fun forum fights you could start with an antique cheapo detector pulling coins at 12-20 inches? Minelab this, Hasbro 250 that...WHATEVER...bite my Super Trooper Bounty Hunter.

Besides, if you're in a 200 year old park and get a silver beep at 18 inches...wouldn't you be just a LITTLE curious?

As for detector brand "loyalty"...I agree, it's a bunch of non sense. The #1 cause of poor detector performance is not knowing your machine.

Still experimenting with the first prototype...a stronger recieve coil has pushed the detection limit to 5-6 inches. I'm begining to suspect it's a quantum thing...the stronger the Rx coil the easier it is to sense changes in the Tx feild. Conversely, a stronger Tx field should give a better response on small objects. Now I just need another 600 feet of 30 ga. wire...

Have to admit, I am having a bit o' fun...the advice I've gotten from others is "Jimmy Seirra will sell you the same thing." I don't want to BUY a coil...it's the challenge of it...any odd ball shape that pops into my head and I don't have to pony up another pile of cash to buy a different design.

 

[MD Dog]

Oy ! Don't get me wrong, I'd dig to China if I could be reasonably sure that what I'll find will be worth it like silver or gold or platinum etc... I've seen some videos Jim, of some guys using a rectangular coil about 12-18 inches in length. This shape intrigued me from the standpoint that I've never seen such coils offered to the general public. With a rectangular shape thats say 3 in. wide x 18 in. long how deep do ya think it would penetrate ? How about pinpointing with such a shape would it be harder or maybe easier due to increased power at center and falling off at ends, maybe ? :P Depth of course is only one aspect of a truly great machine, variety in tones would also greatly enhance its performance, thus increasing target id. Also volumetric intensity, IE; the deeper the quieter and the shallower the louder, or vice versus. Manual control of the power output may or may not be useful

 

[diamondjim]

The 3X18 is the Bigfoot Coil, becoming more and more widely available...it can be purchased right on White's web site now, though I don't think they produce it. I haven't seen one available commercially for BH yet, I'm sure some custom builders can whip up one.

From everything I've read about the coil it's not merely a very long oval version of stock concentric round coils...there's something else entirely going on inside...the description of how it responds is just too different from round ones. Not sure if this is the same concept I'm experimenting with, but mine is begining to respond like the ads for bigfoot.

As for depth, I haven't seen any absolute facts on that either except as mentioned in the ad "comparable in depth to a standard 8 inch coil." My best guess based on possible designs is 9 inches with a fringe zone out around 10" to 12". But it's a "different" kind of 9 inches I think...the rounds we're used to have a decreasing abilty to pick out small objects like dimes at greater depths. This thing maintains a strong field density all the way to limit and then little or nothing beyond.

Also there is no field drop off at the edges...that's a little harder to explain, according to the ads, the field is 3 inches wide and X number of inches deep, squared off at the bottom, like a slab instead of the cones created by rounds. The field isn't actually square at the bottom, but it loses effectiveness at the same depth equally along the enitre coil. I've just figured this part out as it relates to the concept I'm using...this field shape is created at a threshold point of transmission coil power, too much and the feild will cone up like the rounds, to little and it sprays all over the place.

Not making things any clearer am I? The net effect is every sweep gives you a flat line at the limit of the coil instead of a pin point...less overlap needed, wider search area...perfect for doing large almost empty fields. Though I have an idea to shorten up the bigfoot...maybe down to 10 or 11 inches for the same types of general hunting of an 8" round with better coverage at depth, yet maintain the abilty to work in average trashy parks.

I guess there are various ways to pin point with this thing too...worst case you just turn 90 degrees and narrow it down to a 3X3 spot. And there's a really sweet trick to pin point my short bigfoot idea...getting too far ahead...need to get this one working first.

Absolute depth is of course not the end all and be all for a good machine...some of my best finds have been just two inches deep. I hated the old TRs and BFOs BAD...though those tones conveyed far more information than modern machines...maybe time to find a tonal hybrid of sorts? More and more I find myself listening to the very subtle varations of my one tone machine instead of watching a display.

I do like using the old BH as a test bed for ideas...it's a pretty straight forward, basic VLF machine...no programing required. I too am thinking beyond advanced coils to tweak out old BH's...I find absolutely no sense in the hype to fork over more cash for a more expensive machine to hunt rapidly decreasing territory....for what? To keep up with the "jone'es"? No doubt many good advancements have been made...but those are tough to sort out from the hype.

I'm sure everyone has thought, gee I wish the machine would put out a stronger field. Or why doesn't brand X build a more powerfull machine? Maybe some folks, like me, have even wondered about using inline power amps to the coil. But in the end it turns out broadcasting a 6.59kHz tone from new york to london isn't really all that helpfull. In truth, these VLF freqencies have plenty of umff to blow right through miles of dirt...it's what you do with the signal that matters, not producing more of it. It's not the dirt causing depth limits at all, rather the shape of the output field.

 

[MD Dog]

Hey I actually understood pretty much everything you just said Jim. So you can speak english huh.
Now we're getting somewhere, so what can I do to help ? Anything ?