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Using Lower Frequency, Larger Coils For Larger Gold?


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First, I new here so hello and thank you for contributing to this forum.  I just purchased my first detector and am excited to get started in this hobby.  I bought an xterra 705 with the 8x5 18.75khz coil to go along with the standard 7.5khz round coil.  I'm hoping to take some trips looking for gold over the summer, but I live in Texas so I was also looking for a general purpose detector for parks, beaches, dinking around.  I'm thinking this setup gives me a pretty solid all arounder to get started.  

I am wondering about the different coils for these things and how to get the most out of a singe detector.  Obviously, the 8x5 will be my best option for small gold.  My question is whether there would be a benefit to getting something like the 15" 3khz coil for larger or deeper gold?  Would it be useful in this capacity?  Would there be much difference from the stock 7.5 coil?  I suppose I'm trying to ask if there's a way to get a VLF to work more like a PI detector.  I'm guessing I also know the answer, but I'm asking anyway.   What do you guys think?  Useful or money better saved?

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Welcome aboard Matt.

First of all, no combination of coils will give a vlf detector the depth performance of a PI gold machine.  The PI gets it depth because the detection principle primarily utilizes the shear power of the detector combined with the coil to maximize the strength of the detection field “pulse” put into the ground.  Whereas coil size, sensitivity, sophisticated signal processing and minimizing noise are what primarily influence depth performance in “continuous” field vlf induction balance detectors.   It’s actually more complex than that, but in a nutshell, when talking chasing deep gold the PI or ZVT detection principles are the “gold standard” (pun intended).

While going with a bigger coil and lowering frequency will improve raw detection depth, generally speaking, with respect to gold, specifically, you don’t want to do this for two reasons.  First of all, the larger coil will be less sensitive to smaller targets.  99.99 % of the gold you will be chasing will be tiny.  Look at the pic below that I ripped off from Steve the forum admin.  Furthermore, even though the smaller, higher frequency 18.75 kHz coil will have less depth penetration, the higher frequency will be better able to light up shallow micro gold better than the big low frequency coil, because the higher frequency coil is better at “illuminating” small mid conductive targets like small gold (as well as brass, lead, birdshot, and micro aluminum bits, unfortunately).  But no one said gold detecting would be easy.  :smile: HTH

I would only consider 15”, 3 kHz coil for coin shooting or relic hunting in mild ground or on the beach.

BTW just curious why you went with the older X-Terra 705 instead of the Vanquish or Equinox 600/800? It is an unusual choice nowadays considering the value and versatility of the Vanquish and Equinox lines (for gold, beach, coin, and relic hunting) and their use of cutting edge but affordable Multi IQ multifrequency technology.  The 600 with its versatile 11” stock coil, sits right at about the same price point as a new 705 with two coils and the Vanquish Pro Pack with two coils, just below.  To be sure, the 705 is a solid, proven detector and should serve you well as you learn the hobby, especially if you got a good deal, used or otherwise.  
 

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The advice Chase Goldman has given above covers most of your post. I would add that most of mine and friends finds are easy targets for standard coils, the uses of large coils is for getting the rare ones (nuggets, jewellery and coins) that are missed and in deeper ground and require a lot experience under your belt first. When you get the experience it will be worth up grading the detector. Lets hope Midas smiles on you.

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2 hours ago, Chase Goldman said:



While going with a bigger coil and lowering frequency will improve raw detection depth, generally speaking, with respect to gold, specifically, you don’t want to do this for two reasons.  First of all, the larger coil will be less sensitive to smaller targets.  99.99 % of the gold you will be chasing will be tiny.  Look at the pic below that I ripped off from Steve the forum admin.  Furthermore, even though the smaller, higher frequency 18.75 kHz coil will have less depth penetration, the higher frequency will be better able to light up shallow micro gold better than the big low frequency coil, because the higher frequency coil is better at “illuminating” small mid conductive targets like small gold (as well as brass, lead, birdshot, and micro aluminum bits, unfortunately).  But no one said gold detecting would be easy.  :smile: HTH

 

Yeah, I was thinking more like going over an area with each coil.  One to compliment the other's weaknesses.  I'm just not sure if it really makes enough difference to justify.  Just trying to figure out how big the difference is between what these two coils would return.

I chose the 705 because my understanding at least was that it would do a better job at finding small gold than something like the vanquish models.  The equinox 800 was a finalist, but a little more than I wanted to pay.  I ultimately decided on the Fisher F19 or equivalents or the 705.  This was just the first one I found a good deal on.  

I'll probably be toting my wife along on most trips so I'll be looking to add a second one.  I'll either go with a similar "value" model or get an equinox 800, or just start saving for a PI who knows.  

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1st off Matt,  Welcome to the finest and most informative gold nugget detecting forum in the US...and has been for it's lifetime.

2nd, If you have a lady (your wife) who enjoys going along on such detecting adventures, hats off to you...you have what most of us don't.

X-Terra 705.  Did you make a mistake on its purchase?  Really doesn't matter, it's old business now and over with.  But how to get the most out of that detector for chasing gold.

As Chase mentioned, the most important part of coil selection is for the size of gold and what reality is of the gold you'll be finding.  Small 6" round HF coil is best for small pickers.  10" ellip HF is good for ground coverage in semi rough terrain and the 9" round HF (not the 7.5 kHz 9" round) is great depth in non mineralized soils (not very often, but some tailing piles when hunting marble size nuggets and above.  Is a 15" round HF coil the best for bigger deeper gold.  Most certainly, but also the hardest to find and most rare.

My suggestion to you.  Go do it a few times with small 6" HF coil and the 10" Ellip coil and see how much fun you enjoy digging lead.  If finding small bird shot lead gets you excited, then I know you have the patience to be a gold hunter.  

If your next go around for a detector is in the near future (within the next year), at that time step up to the Equinox 800 and you'll have a detector that can be used in salt water beaches, better than the detectors you mentioned, is a better coin/relic detector than ones mentioned and also a better nugget unit than what you mentioned.  Don't worry about that...until that time arrives though.

Lead is your friend and small #8 and #9 birdshot lead find shows your proper coil control and operating of the detector.  Keep chasing those and sooner or later the detector will mess up and you'll actually dig a piece of gold.

All pictures are some of my X-Terra 70 and 705 gold finds.  I used the HF - 18.75kHz coils of different sizes for all kills.

We look forward to hearing of your adventures and seeing success when it happens.

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Thanks for the tips.  Maybe I should have posted this before buying, huh?  Haha, that's okay I would guess that I can sell it for the same price I bought it for with no problems.  If you say the Equinox 800 is better at finding gold (including very small) then that looks like the all arounder I'm looking for.  

I actually didn't realize that the vanquish models had Multi IQ.  Their pricing looks pretty attractive.  My main concern is that I don't want to miss small gold.  We go to Colorado every year and should be able to find some pickers where we already go.  I have no idea what else we will do, but beach, coin and relic hunting are all likely.  

 

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16 hours ago, Gerry in Idaho said:

This 1 pound Idaho Potato (as it's called) is 12.73 ozt and has 3.56 ozt of gold in it.  I found it in hand dug rock stack placer piles with the X-705 and 10" Ellip coil.

It is my largest Idaho piece to date, so yes the X-705 has a special place in my heart.

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Welcome aboard and as you can see there are plenty of people on here to give you an honest answer to your questions.

When you get a chance please post some of your finds for everyone to see your adventure.

Where are you located?

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14 hours ago, Matt Wilson said:

Thanks for the tips.  Maybe I should have posted this before buying, huh?  Haha, that's okay I would guess that I can sell it for the same price I bought it for with no problems.  If you say the Equinox 800 is better at finding gold (including very small) then that looks like the all arounder I'm looking for.  

I actually didn't realize that the vanquish models had Multi IQ.  Their pricing looks pretty attractive.  My main concern is that I don't want to miss small gold.  We go to Colorado every year and should be able to find some pickers where we already go.  I have no idea what else we will do, but beach, coin and relic hunting are all likely.  

 

Wecome, Matt!  IMO the X-Terra 705 is a better choice than the Vanquish for one over-riding reason -- it has adjustable ground balance and the Vanquish models don't.  (I know that the hard way, well maybe better said "the soft way" since I got it wrong in a thread/discussion regarding the Vanquish here on this site a few weeks back.)

You said the Equinox 800 was out of your price range, so that eliminated it.  I'm definitely one who sticks to my budget.  A lot of people argue that you spend more and that you should start with the biggest and best.  Not I.  "You get what you pay for" sounds good, and it's right except when it's wrong.

Even more pertinent, though, is that of the three components of detecting, the detector comes in third after 1) site/location and 2) skill/capability of the person swinging the detector.  (Note that research, very important, is a combination of 1 and 2.)

I have an X-Terra 705 but never used it for gold detecting, where I've read from more than one reliable source that it is better at that than for other forms of detecting.  (It has a prospecting side and a coins/jewelry/relic side and I only used the second.)  I bought several coils and my favorite was the 6" round DD @18.75 kHz, and I was coin hunting.  I suspect the 5"x9" DD @18.75 kHz would have worked as well or better for me but I only bought that late in the game to 'complete' my package.  So you are set.

Bottom line -- you have a good detector for the job.  Don't doubt it.  Learn to use it, find (with research) a good place to detect and go have fun!

P.S. You said you are in Colorado.  I heard they have a state-wide gold prospecting club that researches available -- meaning unclaimed -- properties and shares their findings with members.  I'm pretty sure Jeff McClendon (member here) knows of them and maybe belongs.  He can give you more info.  I would PM him; he won't bite.  😁

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