elipticle coil question.

Am I right in my thinking that with the elipticle coils that the width equates to the sensitivity and the depth where the lengths eqates to ground coverage, for example a 12x8 elipticle would have similer depth and sensitivty to the 8" round but covers more ground. I know that this sounds like a real simple question that the average person should know the answer to, but I was asked the other day and I have never owned one and realy dont know for sure,

cheers mikez

You're wrong mikez, it's not a simple question and the average person doesn't know the answer. Many times people have tried to work out the exact formula of an elliptical coil as compared to a round one, but I don't really know of how the exact answer is worked out. Some people square the width and add the square of the length and then square root them. Others subscribe to the formula you wrote. I believe something similar to what you wrote, that the depth is equal to the width of the elliptical plus about 1/3 the difference of the width as to the length ie in your example of the 12x8, the depth would be 8 + 1/3 of 4 so about 9.3". The footprint would be equal to the 12 but because the cone is dragged in to the depth of that of a 9.3 coil and not that of a 12" coil, then the angle would be somewhat sharper than that of a 12" coil, hence slightly deeper targets that a close to the front end of the coil that may be just detected with a 12" round, may be missed with the 12x8" elliptical. All theory, not sure if it's how it actually works in the real world, but it makes sense to me until someone can prove to me differently.

thanks costasdee, now I dont feel so bad as telling my mate I didnt know, maths has never been my fort'e

No worries mikez, but keep in mind that the formula I use is only a very rough guide as if you had a NF 30x6 patchfinder coil, you wouldn't really expect the depth of a 6 + 24/3 = 14" coil, you'd probably get the same as 7 or 8 or maybe 9" round coil. It is a rough guide when it's an elliptical coil that is about on a 3 to 2 ratio or less.