Coils being tuned (or designed) to be "in-spec" Vs tuning a coil-and-detector together. New
Posted by: Monte [ Send a Message ]
Date: November 25, 2012 06:19PM
Registered: 8 years ago
Posts: 4,777
Search coils can be 'tuned' within certain specifications. By design, some manufacturers have a little "sloppier" tuning allowances while other coils follow a much tighter or more controlled set of 'specs.' In the internal winding alignments is out-of-whack, the coil can easily fail to perform well, or at all. The same applies to failure with any internal electronic components in the search coil. Dropping a search coil on a hard surface, smacking it hard against a tree or rock, or even some cases of temperature extremes can cause misalignment's or make a coil fail.
So, each manufacturer has their own design criteria to follow in their coil design allowances in order for them to work with the manufacturers detector circuitry design and operating frequencies.
Most manufacturers check a detector and coil combo and make sure they ought to be compatible before shipping, and then they are off to get boxed up as a checked-and-tuned pair (detector and coil). In this case, the detector itself has to pass the test to make sure it functions properly, and is then checked with the assigned search coil. If it is a factory preset GB model, then they set the GB to their desired spec with that coil to work in their determined level of iron mineralization.
Unfortunately, we face several challenges with this type of design, such as the following.:
a.. We trust that the detector and coil are each functioning within 'spec.'
b.. We trust that the factory-set Ground Balance will provide good functional performance in BOTH the All Metal mode AND Discriminate mode.
c.. We have to hope that, by design, the Disc. and All Metal modes function well with a similar GB setting.
d.. We also hope the manufacturer has provided and internal GB trimmer that a savvy detectorist can easily adjust to tweak the detector for peak performance in radically different ground than what the factory set-up instructions will handle.
The next thing that we could benefit from is having an assortment of search coils that share very 'tight specs' which lets them be highly functional on an assortment of metal detectors designed to operate withing their design criteria. With some makes of coils, they see to have a little more 'slop' in their design and at times that can mean too much variance from a tight design specification. Due to the variables in detector and coil design, and having used a LOT of detectors in my 48 years of detecting, and being a multi-line dealer most of the time since '77, I have found the following to be true.
1.. With some brands, I can try maybe 10 search coils on the same detector, even the same size coil, and I am able to set the Ground Balance and have the detector work. However, I might notice a pronounced difference in the perceived performance between one or more search coils of similar size and type. They work, and they are not noisy or erratic, but some might seem a bit 'hotter' and others are perhaps a little weaker performing.
2.. With some brands, they have very tight specifications for the search coils as well as specific operating frequency that is crystal controlled or otherwise established at a tight setting. Equally, their search coils have a very rigid specification design. If I switch an assortment of search coils around I might have one of two things happen. They all work, work well, and are not noisy, or there might be a coil or two that doesn't seem to perform well and the operation is unstable. Usually, this is a case where the coil is just "out-of-spec" and even adjusting the GB will not result in proper performance.
In the end, regardless of the brand of detector and coil we choose to use, we need to make sure they are a quality-built product and then learn them and know their strengths and weaknesses. There is no such thing as a 'perfect' detector so we have to appreciate each detector we chose to use for its abilities for our needs, then learn and know how to get the most out of it. When it comes to Tesoro models, I have reached the following conclusion, all based upon the facts that I most often hunt in moderate-high to very-high iron mineralized sites.
I know that:
A.. I do not like, and haven't had good performance in a variety of ground environments with, the Cort
