Equinox Coils

[Steve Herschbach]

1 hour ago, Andy2640 said:

Hi Steve, good to talk with you, long time reader.

May i ask, what depth difference do you think the larger coil will provide? and im interested in your comment regarding you not wanting the larger coil for depth?

Its my own logical fallacy perhaps that is motivating my question, because in my noob mind, im thinking depth - or lack of, is the reason for less roman finds.

Thanks in advance.

I will take the extra depth if I can get it. It is just that I have learned that larger VLF coils do not add depth like large PI coils can except on the mildest of ground. If the ground is bad at all larger VLF coils “see” more ground and more trash. That in turn often means sensitivity must be reduced a little with larger coils. This trade is such that really large VLF coils really don’t work well at all compared to what you see on PI detectors.

Also consider that when taking depth of elliptical versus round, using the smaller dimension gives a clearer picture of comparative depth. A 12” x 15” coil gives depth more comparable to a 12” round coil than a 15” round coil. You have taken a 12” coil and stretched it for more ground coverage. It is not like you squish a 15” round coil and retain all the depth.

Manufacturers know you tend to focus on the larger number, so I fight that by putting the smaller number first - it is a 12” x 15” coil in my mind, not a 15” x 12” coil.

Therefore when I look at an 11” round and a 12” x 15” coil my mind is comparing 11” to 12” and guess what - not a mile more depth but instead just a little more depth.

In favorable conditions you might see a 10 - 15% depth edge on coin size targets going from a VLF stock coil to a “large” VLF coil. In poor ground depth may be about the same. In the worst ground, you may lose depth with a larger VLF coil!

Long story short the reason I personally consider large coils is for better ground coverage with extra depth, if any, a bonus.

That’s just how I look at large VLF coils. They have rarely proven to be the magic bullet I was hoping for and in fact usually screw up weight and balance more than they are worth on a VLF.

Another way to explain it. I have almost always found a small coil to be a great investment that puts more finds in my pocket. Large VLF coils - not so much.

[Andy2640]

Howdy Steve,

Many thanks, you have really given me a wake up call and pointed things out that i didnt consider.  Its particularly interesting what you said about the nature of elliptical coils.  In essence,  it is a 12 inch coil with more ground coverage ? .  So in short ,this new larger coil will give me a very small increase in depth, but the main thing is that it will cover more ground.   Got it!

In reevaluating these coils, i may get both eventually.  The big one for the large fields in the UK , and the small for around the Manor house's little steps and crevices.  

Lol ...  Why i didnt consider the larger coil to just be comparable to a 12 inch coil vs the stock 11 inch (in terms of depth capability) has got me scratching my own noggin ?  I think it was the pictures of the size of the thing and as you say, the marketing that says 12 x 15, with the number > (15) (EDIT: Sorry 15) ...  residing deep in my psyche !!  

 

Steve on another note if i may, which i will keep brief as i dont want to take too much of your time up.

Its this: 

What method would you suggest for ground balance in the UK on fields.  When ive manually adjusted, ive had numbers crazy high, like 55, 60 70.  Is ground tracking a good option? or a manual balance say every 20 mins or so ?

Thanking you kindly Steve,

Andy.

[Steve Herschbach]

Best bet is to take that last question and post it as a new thread so our UK members will see it and respond. I have no idea what ground balance method works best in the U.K. I use auto (the pump method) with tracking off myself.

Another note on large coils. My post you first reference is discussing using large coils to hunt trashy parks. The problem there is large coils increase the chances of multiple targets under the coil at one time. This in turn increases the risk of target masking (bad targets hiding good targets). Equinox has an advantage here versus the CTX for instance, because it’s much faster recovery speed can help fight the masking. The problem still exists however and due to masking alone I think getting “more depth” in dense trash is basically impossible with a larger coil. Again, counter intuitively, a small coil may see between the trash better and therefore punch deeper than the larger coil.

Large VLF coils are best for wide open spaces with sparse targets like a huge beach or in your case, a huge farm field. And they can indeed get more depth on targets in milder ground, with the best increases being on larger targets.

[Chase Goldman]

14 hours ago, Steve Herschbach said:

Long story short the reason I personally consider large coils is for better ground coverage with extra depth, if any, a bonus.

Exactly!  It's a 15" (round) ground coverage coil with 12" (round) coil depth. (i.e., about the same as the 11" round, depth wise).  Great explanation.

[Chase Goldman]

5 hours ago, Andy2640 said:

Many thanks, you have really given me a wake up call and pointed things out that i didnt consider.  Its particularly interesting what you said about the nature of elliptical coils.  In essence,  it is a 12 inch coil with more ground coverage ? .  So in short ,this new larger coil will give me a very small increase in depth, but the main thing is that it will cover more ground.   Got it!

The thing about the elliptical is it gives you the larger coil ground coverage but at less weight than a 15" round coil, so that is the primary advantage with a slight depth compromise.  15" round gives you perhaps additional depth, but not so much that it is worth the extra weight.  Another way to look at it is giving your 12" coil 15" ground coverage without all the weight.  Small elliptical coils give you the advantage of being able to swing side-to-side in tight spots with only a slight sacrifice in depth vs. it's "round" cousin with a diameter the same as the elliptical long axis.  Also some folks have the mistaken impression that the elliptical shape gives you more "separation".  But target separation on a DD coil is determined by the width of the active coil area (which is the center spine of the coil whether it is round or elliptical) ignoring coil edge effects which typically only come into play with surface or very shallow targets.