gjdevlin: said:
I'm trying to grasp the understanding of the coils.
Welcome to being retired as well s to this great outdoor sport. I've been retired for over a decade now, and have been very involved in this great sport and industry for over 56 years and I can twll you this:
"I have been trying to grasp the understanding of the manufacturers when it comes to coil choices."
When I built my first three Metal / Mineral Locators staring in early '65, they had me wind a search coil that was about 8" in dimeter. Most of the vast array of detectors produced in that era and into the '70s had a 'standard coil' of 6" to 8" in diameter. In the latter '70s and into the early-to-mid '80s, the notable USA manufacturers generally offered their detectors with a 'standard' search coil from about 6" to 8" or maybe 8½", with popular units from Garrett, and the then-new Teknetics and Tesoro featuring 7", 7¼" and 7½" search coils. They were all round-shaped.
Some competitors were also in the ±7" diameter to the common 8" in diameter. Why did they use this size search coil? Simply because they worked just fine, they provided a comfortable weight and balance, and because they fit well in and around brush, metal structures in playgrounds, handled conditions around building rubble as well as operating near metal fences, etc. Not to mention being able to work well in very high-use locations with a lot of lost pocket change in close relationship.
There were some smaller-size coils on the market in the 4", 4½", 5" and 5½" round-shaped size, and most manufacturers also offered some larger-size coils that ranged from 10" to 11", 12", 14", 15" and even 16" in a round-shaped size. Almost all of the search coils after ±1976 were of a CoPlaner or Concentric type and very few Double-D coils were used, for practical known reasons based on performance compared with Concentrics.
Then by 1988 we noted two changes in search coil sizes and shapes and designs being used. We noted more elliptically-shaped coils being used, especially Double-D types, and especially for Gold Nugget Hunting detectors. Also, in '88, White's was the first major detector maker to start shifting to a '950' Concentric coil
(measuring close to 9½" in diameter). It didn't take long before many other manufacturers started using a greater-than-9" coil, or 10", 10½", sort-of-elliptical 7X11 and then a round-shaped 11" coil as 'standard'. That was even on many of their lower-priced to mid-priced models as well as their top-of-the-line series.
What brought about these change? Marketing more than a beneficial in-the-field advantage. Sure, a Beach Hunter
might benefit from a slightly larger-size coil for coverage of a wide-open beach. The same goes for those searching a plowed field, or maybe out in the center area of a big grassy park with minimal masking trash. Coverage was the primary benefit, and to some degree a
little bit of extra depth over a 'standard' coil, depending upon the target size and shape.
However, the majority of the typical metal detecting 'Hobbyists' are into urban Coin Hunting most of the time and a 'standard' coil can provide all the coverage and performance they need. For hunting in tot-lots with metal playground structures, searching renovation projects, around building rubble, maybe a site with dense brush and weeds, or any locations with a lot of trash, closely-located coins, etc., etc., an 'Avid Detectorist' is going to be better-served if they use a smaller-size search coil, and in modestly-littered locations a good 'mid-size' coil can usually work well.
But the marketing folks at many detector making facilities continue to promote "more depth --- more depth", and to achieve that it might take a larger-size search coil. So many consumers are not finding very many desired targets like they hoped to, or used to, and that's because those early era opportunities had a lot of coins lost, but those of us who got an early start found a lot of them, and bringing us up-to-date others have found a lot of what we missed.
My first factory-produced detector the summer of '68 came with a 6" round search coil. From that time to today, the vast majority of the hundreds of thousands of coins I have found came my way when I had a smaller-size coil mounted. Those used to be 5" to 7½", and in the more recent fifteen years the coils have mainly been 5" to 6½" wide.
To
me, with the improvement in detector performance I consider any search coil from 4" to 6½" in diameter to be a
'smaller-size'
coil, and a round coil of 7" to 9" in diameter, or an elliptical coil such as a 5X8 or 5X9½, usually a DD type, are what I consider to be a
'mid-size' coil. For most typical hunting needs, a 'mid-size' coil can also be considered what I would like to be a 'standard' size coil.
gjdevlin: said:
I'm aware the Nokia Simplex+ comes with a 11-inch coil but folks say the 5x9 SP24 coil that comes as an add on in some deals is the one to use. Why is that the case?
As I just explained, too many times the manufacturers have supplied a detector with an 'over-size' search coil as 'standard' rather than a 'proper' sized coil for general-purpose hunting.
To
me, the Garrett Apex and AT MAX should have used the 5X8 DD as standard. The Minelab Equinox should have used something like the 5X8 DD for their Vanquish as a 'standard-size' coil. The Nokta / Makro Anfibio Multi could have used the round 7" Concentric or 5X9½ DD as a 'standard' coil, and the same goes for the Simplex +.
Notice how many Simplex + users have added the 5X9½ DD SP24 coil and speak highly of it, and how many of us keep it mounted as a primary-use coil on their Simplex +? That's because it works quite well and, in all seriousness I feel it should have been an early design and used as the 'standard' coil.
Just my personal views of the Simplex + coil as well as how things have been going for too long. Let's get back to 'normal-size' standard search coils. If someone wants a bigger coil, let them buy it down the road.
Monte
